How to Give Insulin to a Diabetic Cat Safely

By Dr Duncan Houston

Giving your cat an insulin injection for the first time can feel intimidating. The dose looks tiny, the needle feels suspiciously sharp, and suddenly every meal, injection and glucose reading seems capable of going wrong.

The reassuring part is that most owners become comfortable with insulin injections surprisingly quickly. Cats also tend to tolerate the injections well because insulin needles are extremely fine.

The real risks are usually not the injection itself. They are using the wrong syringe, confusing insulin concentrations, accidentally giving a second dose, changing the dose without enough information or failing to recognise hypoglycaemia.

Quick Answer

Give your cat exactly the insulin and number of units prescribed by your veterinarian, using a syringe or pen that matches that specific insulin. Confirm that your cat is behaving normally, prepare the insulin according to its product instructions, inject it under the skin and record the dose.

Toujeo® is insulin glargine U-300 and requires particular care. It should be administered from the appropriate prefilled pen, not withdrawn with an insulin syringe, and its dose must not be converted as though it were simply a stronger version of glargine U-100.

Why Does a Diabetic Cat Need Insulin?

Insulin allows glucose to move from the bloodstream into cells, where it can be used for energy.

In a diabetic cat, there is not enough effective insulin to control blood glucose properly. Glucose accumulates in the blood and spills into the urine, causing signs such as:

• Increased thirst

• Increased urination

• Increased appetite

• Weight loss

• Muscle loss

• Weakness

• Reduced energy

• A plantigrade or dropped-hock stance in some cats

Without effective treatment, the cat may become dehydrated, lose substantial muscle and develop diabetic ketoacidosis, or DKA. DKA is a life-threatening complication involving ketone production, acidosis and electrolyte abnormalities.

The aim of insulin treatment is not to force every glucose reading into a perfect range. The practical goals are to:

• Reduce excessive thirst and urination

• Stop inappropriate weight loss

• Maintain normal appetite and activity

• Avoid hypoglycaemia

• Prevent diabetic ketoacidosis

• Support a good quality of life

• Give the cat the best realistic chance of diabetic remission

Which Insulins Are Commonly Used in Cats?

Several insulins can be used in cats, but they are not interchangeable. They differ in concentration, duration, handling, administration device and suitability for individual patients.

Insulin	Common brand examples	Concentration	Typical feline use and important points
Insulin glargine U-100	Lantus®, Basaglar®, Semglee®	U-100	A common first-choice insulin. Usually administered every 12 hours. It is a clear solution and is used extra-label in cats.
Protamine zinc insulin	ProZinc®	U-40	Veterinary-approved for cats. Usually administered every 12 hours using a U-40 syringe. The vial must be gently rolled before drawing the dose.
Insulin glargine U-300	Toujeo®	U-300	A concentrated basal insulin with a relatively flat action profile. It is used extra-label in cats and must be administered with the appropriate prefilled pen.
Porcine lente insulin	Vetsulin®, Caninsulin®	U-40	Veterinary-approved. Usually administered every 12 hours in cats. It may have a shorter duration than glargine or PZI and must be shaken until uniformly milky.
Insulin degludec	Tresiba®	U-100 or U-200	A basal insulin used in selected cats. It requires an appropriate pen and veterinary-specific dosing instructions.

Current feline diabetes guidance identifies glargine U-100 and PZI as the most common starting choices because they generally provide an appropriate duration of action and are associated with reliable glycaemic control. Lente insulin remains an option, but its shorter duration means it is not routinely preferred as the first choice by the current AAHA task force.

A note about starting doses

For most cats starting glargine U-100 or PZI, current AAHA guidance commonly begins around 1 unit per cat every 12 hours. Toujeo® is different because it is a basal U-300 insulin and its initial dosing may be calculated from the cat’s estimated lean or ideal body weight.

These are veterinary reference points, not instructions for owners to calculate or alter insulin doses. The dose must be selected using the cat’s diagnosis, glucose data, body weight, concurrent diseases, food intake and previous treatment history.

What Is Toujeo® and Can It Be Used in Cats?

Toujeo® is insulin glargine at a concentration of 300 units per millilitre, commonly described as glargine U-300.

It is approved for people rather than cats, so feline use is extra-label. Current feline guidance recognises that Toujeo® can control hyperglycaemia, reduce daily glucose variability and support remission in some cats. It is not yet as widely used as glargine U-100 or ProZinc®, but it may be considered for newly diagnosed cats and some difficult-to-regulate patients.

Toujeo® has a relatively flat or “peakless” action profile. Its effect may last long enough for once-daily administration in some cats, while other cats require it every 12 hours. That decision should be based on continuous glucose monitoring and the cat’s clinical response rather than convenience alone.

A small prospective study evaluated Toujeo® in diabetic cats. Clinical signs and fructosamine concentrations improved, and four newly diagnosed cats entered remission during or after the study. However, the study was small, so larger and longer comparative trials are still needed.

Toujeo® is not simply “three times stronger”

Toujeo® contains three times as many insulin units in each millilitre as glargine U-100. However, it forms a different subcutaneous depot and has different absorption characteristics.

This means:

• Do not divide a glargine U-100 dose by three

• Do not multiply a Toujeo® dose by three

• Do not convert between Toujeo® and another insulin at home

• Do not assume the same numerical dose will behave identically

• Do not draw Toujeo® out of its pen with a syringe

Current AAHA guidance treats glargine U-300 as a separate insulin type rather than a simple concentrated replacement for glargine U-100.

Which Toujeo® pen is suitable for a cat?

Toujeo® SoloStar delivers insulin in 1-unit increments.

Toujeo® Max SoloStar delivers insulin in 2-unit increments and is intended for much larger human doses. Its 2-unit adjustment steps are generally too large for the small doses and careful adjustments commonly required in cats.

When Toujeo® is prescribed to a cat, the veterinary team should confirm the exact pen, needle length, dose and administration schedule. The owner should never substitute another Toujeo® device simply because it contains the same insulin.

Why Do U-40, U-100 and U-300 Matter?

The “U” number tells you how many insulin units are contained in 1 millilitre.

Concentration	Units in 1 mL	Correct administration device
U-40	40 units	U-40 insulin syringe or the product’s veterinary pen
U-100	100 units	U-100 insulin syringe or compatible pen
U-300	300 units	Product-specific prefilled pen when using Toujeo®

A U-40 syringe and a U-100 syringe have different spacing between the dose marks. Drawing U-40 insulin into a U-100 syringe, or U-100 insulin into a U-40 syringe, can result in a major overdose or underdose.

The safe rule is simple:

The insulin concentration and the syringe concentration must match exactly.

Toujeo® is the exception because it should remain in its prefilled pen. The dose window already displays the number of insulin units being delivered, so no volume conversion is required.

What Equipment Do You Need?

Before beginning, prepare:

• The correct insulin

• The correct matching syringe or insulin pen

• A new sterile needle

• A puncture-resistant sharps container

• Your cat’s prescribed dose and schedule

• An insulin treatment log

• Food or an appropriate reward

• A veterinary emergency contact number

• Plain glucose or corn syrup for a hypoglycaemic emergency

• A veterinary-calibrated glucometer or continuous glucose monitor if prescribed

Keep the insulin, syringes and written dosing instructions together in one clearly labelled location. This reduces the chance of another household member using the wrong product or giving a duplicate dose.

How to Give Insulin to a Cat With a Syringe

Your veterinary team should demonstrate the complete procedure before you attempt it alone. Practising with sterile saline can also help you become comfortable with holding the syringe and giving a subcutaneous injection.

Step 1: Confirm the insulin and dose

Before every injection, read:

• The insulin name

• The concentration

• The prescribed number of units

• The scheduled time

• The syringe type

Do not identify insulin solely by the colour of the box, cap or label. Packaging can change, and several insulin products look similar.

A written or digital log is particularly important when more than one person shares responsibility for the cat.

Step 2: Check your cat

Before giving the full prescribed dose, ask:

• Is my cat alert and behaving normally?

• Has my cat eaten or shown normal interest in food?

• Is my cat vomiting?

• Is my cat weak, wobbly or unusually sleepy?

• Could someone else have already given the insulin?

• Is there any possibility the previous dose was given late?

A cat that is not eating, is vomiting or seems unwell needs individual instructions. Depending on the insulin and circumstances, the dose may need to be reduced or skipped while veterinary advice is obtained.

Step 3: Prepare the insulin correctly

Different insulins must be handled differently.

ProZinc®

Gently roll the vial between your hands until it has a uniform cloudy white appearance.

Do not shake or vigorously agitate it. Do not use the vial if persistent clumps or visible white particles remain after gentle rolling.

Vetsulin® or Caninsulin®

Shake thoroughly until the suspension is uniformly milky. Allow surface foam to disperse before drawing the dose.

Do not use the product if visible clumps or large white particles remain after thorough mixing.

Glargine U-100

Glargine is a clear solution rather than a suspension. It should remain clear, colourless and free of visible particles.

Do not vigorously shake it.

Toujeo®

Toujeo® is also a clear solution. It remains in its prefilled pen and does not need to be drawn into a syringe or resuspended.

Step 4: Draw the prescribed dose

When using a vial:

1. Remove the syringe cap carefully.

2. Pull the plunger back to draw air equal to the prescribed insulin dose.

3. Insert the needle through the vial stopper.

4. Push the air into the vial.

5. Turn the vial and syringe upside down.

6. Keep the needle tip within the insulin.

7. Draw slightly more insulin than required.

8. Tap the syringe gently to move bubbles towards the needle.

9. Push the bubbles and excess insulin back into the vial.

10. Align the correct dose mark with the leading edge of the rubber plunger.

Small bubbles can create meaningful dosing errors when a cat receives only one or two units. A 0.3 mL syringe with half-unit markings can make small doses easier to measure accurately.

Step 5: Choose the injection site

Use the location demonstrated by your veterinary team. Common sites include areas of loose skin along the side of the chest, flank or back.

Rotate sites rather than injecting into exactly the same spot every time. Repeated injections into one small area can cause local irritation or tissue changes and may make absorption less predictable.

A simple rotation might be:

• Morning: left side

• Evening: right side

• Next morning: slightly further forward

• Next evening: slightly further back

Step 6: Give the injection

1. Part the fur so you can see or feel the skin.

2. Gently lift a fold of skin to create a tent.

3. Hold the syringe like a pencil.

4. Insert the needle into the base or side of the skin tent, not through the top.

5. Keep the needle directed beneath the skin rather than towards the spine.

6. Press the plunger completely.

7. Remove the needle smoothly.

8. Release the skin.

9. Reward your cat.

The entire injection usually takes only a few seconds.

Step 7: Check whether the dose went in

Run your fingers over the fur near the injection site.

Wet fur, a medicinal smell or insulin visible on the coat may mean some or all of the dose missed the skin. This is commonly called a fur shot.

Do not immediately give another full dose.

You cannot know how much insulin entered the cat, and repeating the injection could cause an overdose. Record what happened, monitor your cat and contact the veterinary team for advice. When advice is not immediately available, the safer general approach is to wait until the next scheduled dose rather than attempting to replace an uncertain dose.

Step 8: Dispose of the syringe safely

Place the used syringe directly into an approved sharps container.

Do not:

• Leave used syringes on a bench

• Place them loose in household rubbish

• Allow children to handle them

• Reuse a blunt or contaminated syringe

• Attempt to straighten a bent needle

Follow local regulations for disposal of the full sharps container.

How to Give Toujeo® With a SoloStar Pen

Toujeo® requires a different technique from an insulin vial.

1. Confirm the correct pen

Check that the label says:

• Toujeo®

• Insulin glargine

• U-300

• SoloStar

Do not rely on the pen’s colour alone.

2. Inspect the insulin

The insulin should appear clear and colourless, without particles or cloudiness.

Do not use the pen if:

• The insulin is cloudy

• Particles are present

• The pen has been frozen

• The pen has overheated

• The pen has been dropped or damaged

• You are unsure whether it is working correctly

3. Attach a new needle

Use a new sterile pen needle for every injection.

Very short human pen needles may not reliably pass through a cat’s thick coat. Current veterinary guidance suggests that a 10 to 12 mm pen needle may be more appropriate for many cats, but the veterinary team should select the needle for the individual patient.

4. Perform the safety test

Toujeo® SoloStar should be primed before every injection so you know that the pen and needle are working.

The current SoloStar instructions direct the user to:

1. Dial 3 units.

2. Hold the pen with the needle pointing upwards.

3. Press the injection button fully.

4. Confirm that insulin appears at the needle tip.

If insulin does not appear, repeat the safety test according to the product instructions. Replace the needle if it may be blocked. Do not use a syringe to extract insulin from a pen that is not working.

5. Dial the prescribed number of units

The dose window displays insulin units.

Do not:

• Convert the dose to millilitres

• Multiply or divide the number

• Count clicks instead of reading the window

• Use a U-100 or U-40 conversion chart

• Alter the dose without veterinary instructions

6. Inject the dose

1. Lift the skin as demonstrated by your veterinary team.

2. Insert the needle beneath the skin.

3. Press the injection button completely.

4. Keep the button depressed until the dose window shows 0.

5. Count slowly to five.

6. Remove the needle from the skin.

Holding the pen in place is important. Removing it too early can leave insulin dripping from the needle and result in an incomplete dose.

7. Remove the needle after every injection

Use the outer needle cap to remove the needle carefully, then place the needle in a sharps container.

Do not store the pen with the needle attached. Leaving the needle on can allow leakage, air entry, contamination or inaccurate dosing. Replace the pen cap after use.

Where Should Insulin Be Injected?

Insulin is given subcutaneously, meaning beneath the skin rather than into a muscle or vein.

The ideal site is one where:

• The owner can see or feel the skin clearly

• The cat remains comfortable

• The needle can pass fully beneath the skin

• The exact site can be rotated

• The fur does not hide the injection completely

The loose skin over the side of the chest, flank or back is often easier than repeatedly using the thickest part of the scruff.

What matters most is consistency of technique. An injection given through a dense clump of fur is more likely to become a fur shot than one given where the skin has been properly identified.

Ask the veterinary team to clip a small demonstration patch when necessary. A tiny patch of missing fur is considerably less exciting than twelve hours spent wondering whether the insulin went into the cat or the carpet.

Does a Cat Need to Eat Before Every Insulin Injection?

Meal feeding is preferred for many diabetic cats because it makes appetite easier to monitor and supports consistent calorie intake. However, cats do not always eat two large meals on command, and some diabetic cats continue to graze throughout the day.

Current feline guidance states that meal feeding is not essential for every cat. Free-choice feeding may be acceptable when the daily ration is measured and the eating pattern is reasonably consistent. Strict meal timing is also less important with basal insulin such as Toujeo® because it has a flatter profile and does not need to be matched to a sharp post-meal peak.

That does not mean appetite can be ignored.

A diabetic cat that suddenly refuses food may have:

• Nausea

• Pancreatitis

• Infection

• Kidney disease

• Diabetic ketoacidosis

• Hypoglycaemia

• Another concurrent illness

If your cat is not eating or drinking, is vomiting or appears unwell, contact your veterinarian before giving the usual full dose. Current AAHA guidance advises reducing or skipping insulin when necessary to avoid hypoglycaemia, but also warns that a diabetic cat should not remain without any insulin for more than approximately 24 hours without veterinary assessment.

Every diabetic owner should have written instructions covering:

• What counts as an adequate meal

• What dose to give after a partial meal

• What to do after a completely missed meal

• What to do if vomiting occurs

• When to check glucose

• When to check ketones

• When the cat needs examination

How Should Insulin Be Stored?

Insulin can lose effectiveness when it is frozen, overheated, exposed to prolonged direct light or handled incorrectly.

Product-specific instructions matter because not every insulin has the same storage requirements.

Insulin	General storage guidance
ProZinc®	Refrigerate upright at 2°C to 8°C. Do not freeze. Protect from light. Current US labelling specifies 60 days after first puncture for the 10 mL vial and 80 days for the 20 mL vial.
Vetsulin®	Refrigerate upright at 2°C to 8°C. Do not freeze. Protect from light. Use within 42 days of first puncture under the current US label.
Glargine U-100 vial	Keep unopened vials refrigerated. Current human labelling permits an opened vial to remain refrigerated or below 30°C for up to 28 days, although veterinary instructions may differ.
Toujeo® SoloStar	Keep unused pens refrigerated at 2°C to 8°C. Once first used, store the pen at room temperature below 30°C, with the cap on and needle removed. Do not return an in-use pen to the refrigerator. Discard after 56 days.

Always follow the instructions supplied by the veterinary clinic for the exact product and presentation you have been given.

Replace insulin when:

• It has been frozen

• It has been exposed to excessive heat

• The appearance has changed unexpectedly

• Clumps persist after correct mixing

• Clear insulin becomes cloudy or discoloured

• The pen or vial is damaged

• Diabetic signs suddenly return despite correct administration

• The veterinary team suspects reduced potency

Write the date of first use on every vial or pen.

What If You Miss an Insulin Dose?

Do not double the next dose.

If you realise shortly after the scheduled time, contact your veterinary team because the appropriate response depends on:

• Which insulin is being used

• Whether it is normally given every 12 or 24 hours

• How late the dose would be

• Whether the next injection time can safely be adjusted

• The cat’s glucose and ketone status

• Whether the cat is eating normally

When advice is unavailable and the dose has been completely missed, it is generally safer to wait until the next scheduled administration than to give two doses too close together.

Official ProZinc® guidance similarly advises owners who miss or underdeliver a dose to contact their veterinarian and, when the cat is eating and acting normally, resume the usual dose at the next scheduled injection rather than trying to catch up.

What If You Accidentally Give Too Much Insulin?

Treat a suspected insulin overdose as urgent.

Contact your veterinarian or the nearest emergency veterinary hospital immediately. Do not wait for symptoms to appear because glucose may continue falling for several hours, particularly with longer-acting insulin.

Tell the veterinary team:

• The insulin name

• Its concentration

• The normal dose

• The amount possibly given

• The time it was administered

• Whether the cat has eaten

• The current glucose reading, if available

• Whether any signs of hypoglycaemia are present

Do not induce vomiting. Injected insulin cannot be removed from the body by making the cat sick.

What Does Hypoglycaemia Look Like?

Hypoglycaemia means the blood glucose has fallen too low.

Early or mild signs can include:

• Sudden hunger

• Restlessness

• Unusual vocalisation

• Sleepiness

• Weakness

• A wobbly or drunken gait

• Strange behaviour

• Disorientation

• Muscle twitching

• Trembling

Severe signs include:

• Collapse

• Inability to stand

• Seizures

• Reduced responsiveness

• Unconsciousness

• Coma

Cats may not show obvious warning signs until the hypoglycaemia is already significant. Any neurological or behavioural change in a cat receiving insulin should therefore be taken seriously.

What Should You Do During a Hypoglycaemic Episode?

If your cat is alert and able to swallow

1. Offer several small bites of normal food.

2. Recheck glucose if a suitable meter is available.

3. Contact your veterinarian immediately.

4. Do not give another insulin dose until you have received instructions.

If your cat is weak, trembling or poorly responsive

1. Apply a small amount of plain glucose or corn syrup between the cheek and gums.

2. Use a cotton-tipped applicator or syringe rather than placing your fingers in the mouth.

3. Do not pour liquid down the throat.

4. Allow the sugar to absorb through the oral tissues.

5. Offer food once your cat is alert enough to swallow safely.

6. Travel to a veterinarian or emergency clinic.

A poorly responsive cat can aspirate food or liquid into the lungs. The syrup should be smeared across the gums, not forced into the back of the mouth.

If your cat is unconscious or having a seizure

This is an emergency.

Apply syrup carefully to the gums while arranging immediate transport, but do not place your fingers inside the mouth and do not delay departure while repeatedly attempting to feed the cat.

Hypoglycaemia can recur after the cat initially improves because long-acting insulin may continue working. Veterinary monitoring and intravenous glucose may be required.

Does One High Glucose Reading Mean the Insulin Dose Is Too Low?

No.

A single high reading may be caused by:

• Stress

• Recent food intake

• A poorly timed measurement

• A fur shot

• A failing sensor

• Day-to-day glucose variation

• Insufficient insulin duration

• Rebound after an earlier low glucose episode

• Concurrent disease

A glucose reading above 300 mg/dL is not automatically an emergency in a cat that is bright, comfortable and eating. The cat’s clinical condition and the glucose trend matter more than one isolated number.

Do not increase insulin because of one high result. An excessive dose can cause hypoglycaemia followed by rebound hyperglycaemia, making the glucose appear high despite the cat receiving too much insulin.

How Is a Diabetic Cat Monitored?

A monitoring plan may include:

• Appetite

• Water consumption

• Urination

• Body weight

• Muscle condition

• Energy and behaviour

• Vomiting or diarrhoea

• Home blood glucose readings

• Continuous glucose monitoring

• Urine glucose

• Urine or blood ketones

• Fructosamine

• Periodic blood and urine testing

Current AAHA guidance emphasises monitoring the cat rather than chasing individual numbers. Improved thirst, urination, appetite, body weight and demeanour are major signs that treatment is working.

Continuous glucose monitors

A continuous glucose monitor, or CGM, can provide several days of glucose trends and identify hypoglycaemia that might otherwise go unnoticed.

However:

• Human CGMs are not specifically calibrated for cats

• Low readings should be interpreted alongside clinical signs

• Important results may need confirmation with a veterinary-calibrated meter

• A sensor can produce occasional errors or gaps

• Owners should not alter insulin based on hourly readings without veterinary advice

Current guidance no longer recommends routine in-clinic glucose curves for every diabetic cat because stress can significantly alter feline glucose results. Home monitoring and CGMs generally provide more useful information about the cat’s normal routine.

When should monitoring be repeated?

Glucose monitoring is particularly important:

• Approximately 5 to 14 days after starting insulin

• After a dose change

• When diabetic signs return

• When hypoglycaemia is suspected

• When appetite or body weight changes

• When another illness or medication is introduced

• When remission may be developing

Toujeo® often requires CGM monitoring from the beginning because its dose and frequency may be adjusted more rapidly than traditional non-basal insulin regimens.

How Worried Should You Be?

Situation	What it may mean	Recommended action
Stable	Eating, alert, comfortable and diabetic signs are gradually improving	Continue the prescribed plan and record daily observations
Needs veterinary advice	One missed dose, possible fur shot, persistent thirst, increased urination or uncertain pen technique	Contact the veterinary team during normal hours
Prompt assessment needed	Reduced appetite, repeated vomiting, ongoing weight loss, persistent high glucose, ketones or two reduced insulin doses because of poor eating	Arrange same-day veterinary assessment
Urgent	Weakness, wobbliness, strange behaviour, trembling or suspected insulin overdose	Treat as possible hypoglycaemia and seek urgent veterinary care
Critical	Collapse, seizures, unconsciousness, severe dehydration, breathing changes or profound lethargy	Go to an emergency veterinary hospital immediately

When Is Feline Diabetes an Emergency?

Seek urgent veterinary care when a diabetic cat has:

• Collapse

• Seizures

• Severe weakness

• Inability to stand

• Altered consciousness

• Suspected insulin overdose

• Persistent vomiting

• Complete refusal of food

• Marked dehydration

• Rapid or laboured breathing

• Ketones combined with illness

• Sudden profound lethargy

• A very low glucose result

• Hypoglycaemic signs at any measured glucose level

Poor appetite, vomiting, dehydration, weakness and weight loss can indicate diabetic ketoacidosis. DKA is life-threatening and requires hospital treatment with fluids, insulin, electrolyte support and investigation of underlying disease.

Can a Diabetic Cat Go Into Remission?

Yes.

Diabetic remission means the cat maintains normal glucose without insulin or an oral glucose-lowering medication for more than four weeks.

Remission is not the same as a permanent cure. A cat in remission still has reduced pancreatic insulin reserve and may relapse later.

Current AAHA guidance uses an average feline remission rate of approximately 30% in the United States, although published rates vary according to the population and management protocol. Approximately one-quarter of cats that achieve remission do so within the first two to three months, and most remission occurs within six months of diagnosis.

Factors that may support remission include:

• Early diagnosis

• Effective glucose control

• Close monitoring

• Appropriate insulin adjustment

• A suitable high-protein, lower-carbohydrate diet

• Healthy weight loss in obese cats

• Stopping insulin-antagonising medication when medically possible

• Treating dental disease, pancreatitis or other causes of insulin resistance

The type of insulin matters, but good monitoring and timely adjustment may be more important than choosing one supposedly magical product. Diabetes, annoyingly, refuses to be impressed by marketing departments.

Why remission can create a hypoglycaemia risk

As pancreatic function improves, the cat may suddenly need less insulin.

Warning signs include:

• Falling glucose readings

• Repeated low glucose alerts

• Lower fructosamine

• Loss of glucose from the urine

• A progressively reduced insulin requirement

• Hypoglycaemic behaviour despite an unchanged dose

Never continue giving the previous dose blindly when glucose control has improved dramatically. A cat entering unrecognised remission can develop life-threatening insulin-induced hypoglycaemia.

What Diet Is Best for a Diabetic Cat?

Many diabetic cats benefit from a complete and balanced diet that is:

• High in animal protein

• Lower in carbohydrate

• Appropriate in calories

• Suitable for any concurrent kidney, intestinal or pancreatic disease

• Consistently accepted by the cat

Current AAHA guidance generally favours canned food because it often contains less carbohydrate, supports hydration and makes portion control easier.

However, reliable food intake is more important than forcing a theoretically perfect food that the cat refuses to eat. Concurrent disease may also change the priority. For example, a cat with advanced kidney disease may need a renal diet rather than an aggressively carbohydrate-restricted diabetic diet.

Overweight cats should lose weight gradually. Rapid restriction can cause muscle loss or hepatic lipidosis and may change insulin requirements unexpectedly.

Common Insulin Mistakes to Avoid

Using the wrong syringe

Never use a U-100 syringe for U-40 insulin or a U-40 syringe for U-100 insulin.

Drawing Toujeo® into a syringe

Toujeo® should be administered from the prescribed pen. Removing it with a syringe creates a serious overdose risk.

Repeating a possible fur shot

Some of the dose may already have entered the cat. Wait for veterinary advice rather than guessing.

Giving a double dose

Use a written log, shared app or physical marker so every household member knows whether insulin has already been given.

Changing the dose after one glucose reading

Dose decisions require glucose trends, clinical signs, weight and an understanding of insulin duration.

Failing to prime an insulin pen

A blocked or unprimed needle may deliver little or no insulin.

Removing the pen too quickly

Keep the button depressed and wait for the full manufacturer-recommended injection time.

Leaving the pen needle attached

Remove the needle after every dose to reduce leakage, contamination and air entry.

Mixing insulin incorrectly

ProZinc® is gently rolled. Vetsulin® is shaken until uniformly milky. Clear glargine products should remain clear.

Injecting into exactly the same spot

Rotate sites to reduce local tissue changes and improve comfort.

Assuming every diabetic cat must finish a large meal first

Meal requirements depend on the insulin and the individual cat. What matters is knowing the cat’s normal eating pattern and having clear sick-day instructions.

Ignoring reduced appetite or vomiting

These are not merely inconvenient disruptions to the insulin schedule. They may be early signs of significant illness or DKA.

How Can You Make Insulin Injections Easier?

• Use the same calm location each time

• Prepare the equipment before bringing your cat over

• Give the injection while your cat is eating or distracted

• Keep restraint gentle and brief

• Ask another person to assist initially

• Reward your cat immediately afterwards

• Take a video of the veterinary demonstration

• Practise with sterile saline under supervision

• Keep the routine predictable

• Remain calm when an injection does not go perfectly

Most cats react more to being chased, grabbed or restrained than to the needle itself. Quiet confidence usually works better than turning each injection into a small hostage negotiation.

What Should You Do Next?

Before taking insulin home

Confirm that you know:

• The exact insulin name

• The concentration

• The number of units

• The injection frequency

• The correct syringe or pen

• How to prepare the product

• Where to inject

• How to recognise a fur shot

• What to do if a dose is missed

• What to do if the cat does not eat

• What to do if vomiting occurs

• How to recognise hypoglycaemia

• Who to call after hours

• When the first recheck is due

During the first week

Record:

• Every insulin dose

• Injection time

• Food intake

• Water consumption

• Urination

• Vomiting

• Energy

• Behaviour

• Glucose readings when prescribed

• Any suspected fur shots

Arrange the recommended early recheck. Initial monitoring is particularly important because the dose may need adjustment and some newly diagnosed cats can begin moving towards remission.

During long-term care

Continue monitoring body weight, appetite, thirst, urination and general wellbeing.

Do not allow a well-controlled cat to remain on automatic repeat prescriptions indefinitely without periodic reassessment. Insulin requirements can change because of remission, weight loss, kidney disease, infection, pancreatitis, dental disease, medication or another hormonal disorder.

Frequently Asked Questions

Can I use a human insulin syringe for my cat?

Yes, but only when its concentration matches the insulin. Use a U-100 syringe for U-100 insulin and a U-40 syringe for U-40 insulin. Toujeo® U-300 should be given using its prescribed pen rather than a syringe.

Can Toujeo® be drawn from the pen with a syringe?

No. Toujeo® contains 300 units per millilitre and removing it with a syringe can cause a severe dosing error. Use the pen’s dose window and administer the number of units prescribed.

What should I do if my cat does not eat?

Contact your veterinarian before giving the normal full dose. Depending on the insulin and the cat’s condition, the dose may need to be reduced or skipped. A diabetic cat that remains inappetent, vomits or seems unwell needs assessment for ketosis and concurrent disease.

What should I do after a fur shot?

Do not repeat the full injection. Record the possible missed dose, monitor your cat and contact the veterinary team. Resume treatment according to their instructions.

Do insulin injections hurt cats?

Most cats tolerate them extremely well. The needles are very fine, and many cats barely react when the injection is given calmly while they are eating or receiving attention.

Can my cat ever stop insulin?

Possibly, but only after monitoring confirms diabetic remission. Never stop insulin simply because your cat appears better. Unrecognised remission can also make the existing dose unsafe, so falling glucose or hypoglycaemic signs require immediate veterinary advice.

Final Takeaway

Giving insulin to a cat becomes much easier once the routine is familiar. The key is not speed or bravery. It is accuracy and consistency.

Always confirm the insulin, concentration, device, dose and schedule. Match U-40 insulin with U-40 syringes and U-100 insulin with U-100 syringes. Treat Toujeo® U-300 as a separate pen-administered insulin rather than attempting to convert it from another glargine product.

Monitor the cat as carefully as the glucose. Appetite, water intake, urination, body weight, behaviour and energy often tell you whether treatment is working before one isolated number does.

Most importantly, know the hypoglycaemia plan before you need it. Weakness, wobbliness, tremors, strange behaviour, collapse or seizures in a cat receiving insulin should be treated as urgent.

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If you are uncertain about an insulin dose, a missed injection, a glucose reading or whether your diabetic cat’s symptoms are urgent, ASK A VET™ can help you organise the information and understand what veterinary care may be needed next.