Pet Supplement Dose Calculator for Dogs & Cats

All 85 at a glance

Every supplement in this calculator, with the doses vets actually use and an honest evidence rating — including the ones worth skipping. Ranges are typical published figures for guidance only. Use the calculator above for your pet's exact weight.

How often, and for how long: the schedule cheat sheet

Dose is only half the instruction — the schedule is the other half, and it is where supplements quietly fail. Some are daily forever, some are per meal, some are short courses, and some (like B12) have a completely different vet-given schedule. The calculator shows this for every supplement; here are the ones people get wrong most.

Human supplements that put pets in emergency

This is the part of the supplement aisle a vet worries about. These are not "be careful" items, they are call-the-vet items. Amounts are approximate published toxic thresholds; if in doubt, ring a vet or a poison line with the container in hand.

The label maths nobody does

Most supplement failures are not the supplement failing, they are the maths failing. Three examples this calculator quietly fixes:

A 1000 mg fish oil capsule is not 1000 mg of fish oil that matters

The active part of fish oil is the EPA and DHA. A standard 1000 mg capsule carries roughly 180 mg EPA and 120 mg DHA, so about 300 mg of active omega-3. A 30 kg dog with arthritis needs roughly 2,250 to 3,000 mg of EPA+DHA a day, which is 7.5 to 10 standard capsules. Owners give one or two, see nothing after a month, and conclude fish oil does not work. It never had a chance. Concentrated capsules carry around 600 mg, pet liquids around 300 mg per ml, and krill capsules a modest 90 mg, which is why the calculator asks what is actually on your bottle.

Plain turmeric powder is about 3 percent curcuminoids

Kitchen turmeric is mostly not the active compound. A 500 mg capsule of plain powder holds roughly 15 mg of curcuminoids, while a 500 mg capsule of a standardised 95 percent extract holds around 475 mg. That is a thirty-fold difference between two bottles that look identical, before you even get to the absorption problem, since plain curcumin is barely absorbed without piperine or a phytosome form.

Glucosamine salts are not equal

Glucosamine hydrochloride is about 83 percent glucosamine, while the common glucosamine sulfate potassium salt is about 59 percent. Veterinary products use the hydrochloride. If you are using a human sulfate product, a "1500 mg" dose delivers materially less glucosamine than the same number on an HCl label.

The detail

Fish oil for dogs and cats: the one worth doing properly

Fish oil is the best-evidenced supplement in small animal practice, with multiple controlled trials in arthritic dogs showing improved comfort and, in some studies, reduced NSAID doses. But the dose that achieved that was large: around 75 to 100 mg of combined EPA+DHA per kilogram per day for joints, with lower targets used for skin (roughly 50 to 70 mg/kg), kidneys (55 to 80), heart (around 65) and general wellness. There is also a genuine ceiling: the National Research Council's safe upper limit works out to roughly 370 mg per kg of metabolic weight per day in dogs, and this calculator shows that limit for your dog's weight. High doses can cause loose stool (build up over one to two weeks), affect platelets (mention it before surgery and alongside NSAIDs or anticoagulants), and add real calories. Cats sit lower, usually around 50 to 75 mg/kg and about 200 to 250 mg a day in practice, with higher amounts vet-supervised only. Choose a product with added vitamin E, and never use cod liver oil to chase omega-3 targets, because the vitamin A and D arrive at toxic levels first.

Fish oil dosage chart for dogs (joint dose)

Worked examples at the arthritis target of 75 to 100 mg/kg EPA+DHA daily, using standard 1000 mg capsules that contain about 300 mg of EPA+DHA. Skin, kidney and heart targets are lower; the calculator above works all of them out for your exact weight.

Build up to these amounts over one to two weeks, stay under the NRC safe upper limit the calculator shows for your dog, and remember a joint-support therapeutic diet may already be supplying a large share of this before you add anything.

CBD for dogs and cats: dose, evidence and the legal bit

CBD is the best-studied of the newer supplements, and the honest picture is narrower than the marketing. For arthritis in dogs, 2 mg/kg twice daily improved comfort in small placebo-controlled trials over 4 to 12 weeks — promising, real, not yet definitive. For epilepsy, 2.5 mg/kg twice daily modestly reduced seizure frequency in one trial, strictly as an add-on to proper anticonvulsants. For anxiety, the best-controlled study found no effect at all, and CBD blunted the effect of trazodone given alongside it. Cats absorb it poorly and the feline data is early: one small 2025 placebo-controlled trial in arthritic cats showed pain benefit from a CBD/CBDA paste, with a lot of vomiting dropouts along the way.

Three practical rules. First, the law: in Australia therapeutic CBD for pets is Schedule 4, prescription-only through a vet, and the UK likewise requires a veterinary prescription; in the US it is unregulated and varies by state. Second, quality: independent testing has found products carrying anywhere from 0 to about 54 mg/ml of actual CBD, so only buy something with a batch certificate of analysis and no THC, which is toxic to pets. Third, monitoring: CBD commonly raises liver enzymes and slows the clearance of other drugs, so long-term use belongs alongside blood tests and a vet who knows it is on board. And do not pay CBD prices for hemp seed oil — the seeds contain no CBD at all.

The rest of the joint aisle, ranked honestly

Beyond the big four (fish oil, green-lipped mussel, UC-II and glucosamine), the joint shelf runs long on promise and short on replication. Eggshell membrane at 13.5 mg/kg daily has one well-designed manufacturer-funded trial showing benefit within weeks. Elk velvet antler at 15 to 25 mg/kg daily has one small placebo-controlled trial, never repeated. Boswellia at around 40 mg/kg of a resin extract has a single study with no placebo group. ASU mostly rides along inside Dasuquin at label amounts well below the experimental dose. Hydrolysed collagen peptides have two small trials at wildly different doses, and are not the same thing as UC-II. MSM has no efficacy trials of its own at all, and oral hyaluronic acid appears in chews at token amounts with no trial behind the swallowed route. None of these are dangerous; the question is only ever which ones deserve your money before fish oil is at a proper dose, and the answer is none of them. The same verdict covers the deeper shelf — cetyl myristoleate, rosehip and shark cartilage have no controlled dog trials, shark cartilage adds a sustainability problem, and yucca's saponins irritate the gut when used long-term.

Glucosamine and chondroitin: the honest story

This is the world's most-bought pet supplement and the evidence has quietly collapsed underneath it. Early studies were mildly positive, but a 2022 meta-analysis found a clear non-effect for arthritis pain and a 2023 placebo-controlled trial agreed. It remains safe, with mild digestive upset the main issue and some caution in diabetics, so a supervised trial is not unreasonable, typically 20 to 30 mg/kg of glucosamine daily with double doses for the first four to six weeks. But if you are choosing one joint supplement on evidence, fish oil wins, with green-lipped mussel and UC-II collagen as the better-supported second tier. MSM, often blended in, has no published veterinary efficacy trials at all.

Green-lipped mussel for dogs: the better second-tier joint pick

Green-lipped mussel powder has several supportive dog studies at roughly 25 to 75 mg/kg daily and is a reasonable adjunct in arthritis, with anti-inflammatory omega-3s and glycosaminoglycans doing the work. One conversion trap: the concentrated lipid extract products (PCSO-524, sold as Antinol) are a different, far more concentrated preparation and should be dosed by their own label, never converted from powder figures. In cats the data is thin, with typical products at 150 to 300 mg daily, so run it past your vet. Avoid it entirely in pets with shellfish allergy.

UC-II collagen: one small tablet, whatever the size of the dog

UC-II undenatured type-II collagen is the odd one out in all of veterinary dosing: the studied dose is a flat 10 mg of UC-II once daily, usually one 40 mg tablet, whether the dog is a terrier or a Great Dane, because it works through immune signalling in the gut rather than blood levels. In trials it performed at least as well as glucosamine-chondroitin, and benefit faded within a month of stopping, so treat it as a continuous supplement rather than a course. In cats it has only been tested for tolerability, not effect.

Turmeric: popular, unproven, and easy to get wrong

Turmeric is probably the most-Googled dog supplement and the least deserving of its reputation. The controlled trials in arthritic dogs did not show benefit on objective measures, and the 2022 meta-analysis found no effect. If you and your vet still want to trial it, the empirical range quoted in veterinary herbal references is about 50 to 250 mg of curcuminoids two to three times daily for a dog, always as a bioavailable form, and always away from a growing list of interacting drugs, including NSAIDs and anticoagulants. Do not give turmeric to cats; there are no feline trials and the drug-interaction concerns are real. And remember the maths above: kitchen powder is around 3 percent curcuminoids, so golden paste made from pantry turmeric delivers far less than owners assume.

Melatonin for dogs and cats: dose by size, and the gummy trap

Melatonin is given at roughly 1 to 3 mg for small dogs, 3 mg for medium and 3 to 6 mg for large dogs, up to two or three times daily or 30 to 60 minutes before a storm, fireworks or a car ride, and 1.5 to 3 mg for cats in the evening. The evidence is modest, mostly small studies and formulary convention, but it is cheap and well tolerated. The non-negotiable rule is the format: plain, xylitol-free tablets or capsules only, because many human melatonin gummies and fast-melts contain xylitol, and a handful of those is a genuine emergency for a dog.

L-theanine (Anxitane) for mild anxiety

L-theanine is dosed by weight band: 25 mg twice daily for cats and small dogs, 50 mg twice daily for medium dogs and 100 mg twice daily for large dogs, matching the Anxitane label it was studied under. For predictable events like storms, give a dose about 12 hours before and again 2 hours before. It suits mild fear and stress; it was not designed for, or tested against, severe phobia or aggression.

Zylkene (alpha-casozepine) dose for dogs and cats

Alpha-casozepine, a milk-protein derivative sold as Zylkene, is dosed at about 15 mg/kg once daily, which maps neatly onto its 75, 225 and 450 mg capsules, and the label allows doubling for the first days or major stressors. Start it a day or two before a predictable event such as travel, boarding, fireworks or a house move, or give it continuously for a month and reassess. It has blinded trials behind it in both species, and its only real exclusion is true milk-protein allergy. None of these three calming options fix severe separation anxiety, noise phobia with self-injury, or aggression; those need a vet and a behaviour plan, not a capsule.

Probiotics: strains, not milligrams

Probiotics are the one category where per-kilogram maths is marketing, not medicine. Efficacy belongs to specific strains at the labelled amount: Enterococcus faecium SF68 (FortiFlora) shortened diarrhoea in studies, particularly in cats and shelter settings, and Bifidobacterium longum BL999 (Calming Care) has small supportive studies for anxious behaviour. The dose is simply one labelled sachet or capsule a day, whatever the size of the animal. Choose veterinary products with a guaranteed live count, because independent testing of shop-shelf probiotics has repeatedly found them short of label claims. The interesting newcomer is Saccharomyces boulardii, a probiotic yeast with a placebo-controlled dog trial behind it at 1 billion CFU per kg twice daily — and because it is a yeast, antibiotics do not touch it, which makes it the one probiotic that keeps working mid-course.

Pumpkin for dogs and cats: what it can and cannot do

Pumpkin is the internet's favourite gut fix, and it half-deserves it. Plain canned purée adds soluble fibre and water, which genuinely helps mild soft stool and mild feline constipation: roughly 1 to 4 tablespoons a day for dogs by size, split over meals, and 1 to 4 teaspoons for cats. Two catches. A tablespoon only carries about half a gram of fibre, so pumpkin is a garnish, not a treatment — diarrhoea that lasts more than a day or two, contains blood, or comes with a flat, unwell pet is a vet visit, and genuinely fibre-responsive guts do better on psyllium or a prescription fibre diet. And it must be plain purée: pie filling carries spices, sugar and sometimes xylitol, which is toxic to dogs.

Digestive enzymes: life-changing for EPI, useless for everyone else

Pancreatic enzyme replacement is one of the few entries on this page that is close to curative — for the right patient. Dogs and cats whose pancreas has genuinely stopped making enzymes (exocrine pancreatic insufficiency, diagnosed with a TLI blood test) transform on about a teaspoon of enzyme powder per 10 kg mixed into every meal, usually with B12 alongside. For healthy pets, there is no evidence enzyme supplements improve digestion at all — a normal pancreas already makes plenty. So this one is binary: diagnosed EPI, essential; everything else, marketing. Slippery elm, meanwhile, has tradition and zero trials, and its mucilage can blanket the gut and reduce absorption of real medication, so keep it two hours from any drugs if you use it at all.

Ginger for car sickness

Ginger has genuine anti-nausea evidence in dogs, but from a chemotherapy model using concentrated extracts, not from car-sickness trials. The practical translation is low-dose powdered ginger, roughly 10 to 25 mg/kg, 30 to 60 minutes before travel with a small snack. It affects platelets, so stop it before surgery and mention it alongside NSAIDs or anticoagulants. And if your dog is truly miserable in the car, maropitant (Cerenia) from your vet is the proven fix and worth every cent over kitchen spice experiments.

SAM-e and milk thistle for the liver

SAM-e at 18 to 20 mg/kg once daily raises hepatic glutathione and is a standard adjunct in liver disease, with a separate placebo-controlled trial supporting it in older-dog cognitive decline. It is also the easiest supplement to accidentally neutralise: the enteric-coated tablet must be swallowed whole, on an empty stomach, at least an hour before food. Milk thistle (silymarin) is widely used at 20 to 50 mg/kg daily divided, but clinical trials in real hepatic patients are lacking, so treat it as a safe adjunct with unproven benefit; the silybin-phosphatidylcholine complexes absorb several times better and need less per kilogram, which is why products like Denamarin pair a small silybin amount with SAM-e. One newer arrival to watch: TUDCA, imported from human biohacking, has no veterinary dose or trials — its cousin ursodiol is a real prescription liver drug, so ask your vet about that instead of buying powder.

Taurine dose for dogs and cats: genuinely disease-modifying when deficient

Taurine is the supplement with the best story in veterinary history: supplementing it reversed feline dilated cardiomyopathy in the 1980s and reshaped every cat food on the market. Today it is dosed at 250 mg once or twice daily in cats and 500 to 1000 mg twice daily in dogs under 25 kg, 1000 to 2000 mg twice daily above, typically alongside a cardiology workup in the breeds and diet histories that raise suspicion, including Cockers, Goldens and dogs on grain-free or legume-rich diets. It is extremely safe, but the point is precision: get the echocardiogram and ideally a blood taurine level first, then supplement with purpose.

L-carnitine for dogs and cats

L-carnitine at 50 to 100 mg/kg twice daily supports a documented subset of dogs with dilated cardiomyopathy, classically Boxers and American Cocker Spaniels, and cats get 250 to 500 mg daily as part of vet-run weight management or hepatic lipidosis support. Two rules: always the pure L-form, never D- or DL-carnitine, and treat it as an adjunct inside a cardiology or weight plan rather than a standalone fix. High doses cause diarrhoea and a fishy odour, and canine cardiac doses get expensive.

Vitamin B12 (cobalamin) dose for dogs and cats

B12 is the quiet achiever of this whole page: dogs with chronic gut disease and low blood cobalamin do measurably better supplemented. There are two ways to give it, and the schedule differs completely: the classic protocol is a weekly injection at the vet for 4 to 6 weeks, then monthly; the home route is a daily tablet for about 12 weeks — and a randomised trial showed the daily tablets work as well as the injections for most patients. Either way, blood levels get retested afterwards. Dogs get 250 µg daily under 10 kg, 500 µg from 10 to under 20 kg and 1000 µg from 20 kg, and cats 250 µg daily, for about 12 weeks before retesting. It is water-soluble and essentially non-toxic, which is exactly why the right move is a blood test first, so you are correcting a real deficiency rather than hiding one. Use plain cyanocobalamin, not a multivitamin with added iron.

Cranberry for dogs with recurrent urinary infections

Cranberry extract, standardised on its proanthocyanidins (PACs), has one small positive dog study and one well-designed trial that found no reduction in bacteriuria, so grade it honestly as "may help, probably will not". It is reasonable to trial in a genuinely infection-prone dog at label doses, but never let it delay a urine culture, because recurrent infections usually have an underlying cause worth finding. For cats it is close to irrelevant: most feline urinary disease is sterile stress cystitis, not infection, and a straining cat that cannot pass urine is an emergency, not a supplement conversation.

D-mannose and the cat bladder supplements

D-mannose is popular for urinary infections and has exactly zero dog or cat trials behind it. The circulating dose (about 500 mg per 9 kg, two to three times daily) is borrowed from a single human study, and mechanistically it could only ever matter for E. coli. It must never replace a urine culture and antibiotics for an active infection. On the feline side, N-acetyl glucosamine (Cystaid, Cystease, Cystophan) is marketed for stress cystitis at 250 mg daily loading then 125 mg — and the only placebo-controlled trial found no significant benefit, with both groups improving because owners switched to wet food. That accidental finding is the real prescription: water intake and stress reduction are the treatment for feline idiopathic cystitis, and any capsule is optional garnish. A cat straining and passing nothing is an emergency, tonight, no supplement conversation attached. And for kidney disease, the heavily marketed Azodyl deserves its own honest line: the only controlled study, in CKD cats, found it did not lower kidney values — renal diets, phosphate control and blood pressure care are where kidney money belongs.

PlaqueOff and dental powders: the surprise performer

Ascophyllum nodosum kelp (ProDen PlaqueOff) is the rare pet-shop product with several placebo-controlled trials behind it, showing meaningfully less plaque and tartar in dogs over about 90 days at label doses — one scoop (330 mg) daily under 10 kg, two to 25 kg, three above, and one scoop for cats, where the evidence is thinner. Two caveats: it is a seaweed and carries iodine, so it is off the table for hyperthyroid cats and any pet with thyroid disease; and it reduces plaque, it does not replace tooth brushing or the dental your vet has been recommending. As a low-effort add-on for a pet that will not tolerate brushing, it is one of the more defensible purchases on this page.

Turkey tail mushrooms and cancer claims

The turkey tail story deserves telling straight. A 15-dog pilot in splenic hemangiosarcoma using PSP extract at 100 mg/kg daily showed encouraging survival numbers and made global headlines; the follow-up study did not confirm a survival benefit. It is well tolerated, and as an adjunct alongside a vet or oncologist's plan it is a reasonable conversation. Among the mushrooms, turkey tail PSP is the only one with dog cancer-trial data — maitake's one lymphoma trial failed, and shiitake AHCC's trials are in leishmaniosis, not cancer. But no mushroom treats cancer on its own, and any seller implying otherwise is selling hope to people at their most vulnerable, which is the ugliest corner of the supplement industry. The same warning covers the fenbendazole (dog dewormer) cancer protocol circulating online: no controlled evidence, and it delays real care. Bring it to the vet running the case; never swap it for treatment.

Vitamin E, CoQ10 and MCT oil

Vitamin E has one decent trial in itchy dogs at about 8 IU/kg daily and is often already inside a good fish oil product, which is usually the smarter way to get it. Coenzyme Q10 has no controlled pet trials, so its 30 to 90 mg empirical dosing is faith, not evidence, and it is not cheap faith either. MCT oil has real diet-trial evidence in senior-dog brain ageing, translated practically to about a quarter to half a millilitre per kilogram daily, divided over meals and built up slowly over a few weeks, and avoided entirely in dogs with a pancreatitis history. For the "dog dementia" searches: the branded brain blends (Senilife, Aktivait) are phosphatidylserine-based and carry small supportive trials — a reasonable 6–8 week test in an ageing dog once the vet has ruled out pain, thyroid and bladder disease masquerading as senility. One hard safety line: dog Aktivait contains alpha-lipoic acid, which is toxic to cats, so cats only ever get the CAT-specific version.

Lysine for cats: the one to skip

Lysine for feline herpesvirus is the cautionary tale of the whole supplement industry. It was recommended for years on a plausible theory, then a 2015 systematic review concluded it does not prevent or treat the infection, and some field studies found supplemented cats actually shed more virus. It still sells in every pet shop. Save the money and the daily pilling stress, and put both towards what does help a snuffly cat: vaccination, stress reduction, and vet-prescribed antivirals for genuine flare-ups. This page says so out loud because that is what a veterinary tool is for.

The mushroom shelf, sorted

The mushroom wave has reached the pet aisle, so here is the shelf graded honestly. Turkey tail is the only one with dog cancer-trial data, and its follow-up study disappointed. Shiitake-derived AHCC has real blinded trials, but specifically in canine leishmaniosis as a vet-managed add-on. Reishi has one healthy-beagle immune-marker abstract and a counterfeiting problem (independent testing found around three-quarters of products weren't authentic reishi). Maitake took a proper swing at canine lymphoma and missed. Lion's mane, the loudest one on social media, has zero dog trials behind its "dog dementia" claims. Cordyceps has nothing in pets at all. And chaga is the one to actively avoid: it is exceptionally oxalate-rich, with documented human kidney injury, which is the wrong gamble for stone-prone dogs and every cat. Buying rules for any of them: fruiting-body extracts with a stated beta-glucan percentage, hot-water extraction, never raw or wild mushrooms.

The herbal shelf: one genuine surprise, several vet-only, a few hard nos

The surprise is ashwagandha: it now has several small placebo-controlled pet trials (all one manufacturer's extract, honesty compels) showing lower cortisol and stress scores at 15 mg/kg once daily — making it one of the very few herbs with actual pet dosing evidence. The vet-only shelf: hawthorn is a real traditional heart herb that stacks dangerously with the exact drugs heart patients take; Yunnan Baiyao is used by oncologists for bleeding tumours even though controlled studies keep failing to show it changes clotting or survival; and licorice is a genuinely drug-like herb (it potentiates steroids and shifts potassium and blood pressure) that belongs in short vet-guided courses, as DGL for gut use. Echinacea has one placebo-free study and a hard rule: never in immune-mediated disease. Devil's claw's only dog evidence is a seven-herb combination trial. And the hard nos: elderberry (no pet data, mildly toxic raw plant) and goldenseal (a "natural antibiotic" that mostly delays real antibiotics).

Sardines: the one where food beats capsules

A typical 100 g can of water-packed sardines carries roughly 1,000 to 1,500 mg of EPA+DHA — the same active omega-3s this calculator doses as fish oil, plus vitamin D and soft edible bones. That makes half a can to a can and a half a day a legitimate whole-food joint-and-skin dose for small and medium dogs, swapped against their food rather than added on top. Big dogs hit a calorie wall (a 30 kg dog needs about two cans a day for the full joint dose), which is where concentrated capsules or liquids win. Buy water-packed with no added salt, never smoked or in tomato sauce, and introduce gradually. Cats get half a sardine to one sardine a few times a week as a treat-level top-up.

Kitchen remedies, graded

The kitchen shelf, in one honest sweep. Manuka honey is the standout: medical-grade honey dressings are genuine veterinary wound care with laboratory evidence against wound bacteria, including resistant staph — but that is a vet-guided tube on a wound, not a spoonful in the bowl, and the pantry jar can seed spores into an open wound. Diatomaceous earth does not de-flea a humid dog or deworm a wet intestine, whatever the label promises, and the dust irritates lungs. Pumpkin seeds are a nice snack and a mythical dewormer — praziquantel actually cures tapeworms for a few dollars. Aloe vera juices are unproven for guts while the plant sits on the toxic lists. Oregano oil burns before it treats, and cats cannot clear it at all. Brewer's yeast prevented exactly zero fleas in its 1983 controlled test, and the yeast-and-garlic combination tablets add a toxin to a dud. On the happy side of the ledger: catnip and silvervine are evidence-backed feline joy (79% of cats respond to silvervine, including most catnip non-responders), and a pot of cat grass is harmless enrichment that doubles as lily-avoidance insurance.

Powder, liquid, extract or whole: when the form changes the dose

The same supplement name can hide a thirty-fold potency difference, and this is where owners silently overdose or waste money. The repeat offenders: fish oil is dosed on its EPA+DHA, never total oil, and a standard capsule is only ~30% active. CBD oils are labelled by total mg per bottle but dosed by mg per ml — a "1000 mg" bottle is strong or weak depending entirely on its volume, which is why the calculator asks for your bottle's strength. Plain turmeric powder is ~3% curcuminoids while a standardised extract is 95% — thirty times stronger, gram for gram. Glucosamine HCl is 83% glucosamine but the sulfate salt is 59%, so the same label number delivers different amounts. Mushroom products range from fruiting-body extracts (the studied form) to mycelium-on-grain powders that are mostly starch, and 8:1 concentrates need proportionally less. Herbal doses here are for dried herb or standardised extract as stated — tinctures dose by their own label. Psyllium powder packs about twice as densely as whole husk. Vitamin E's natural form is ~1.5× the synthetic per mg. And plant part matters as much as form: aloe gel versus its toxic latex layer, elderberry's cooked ripe berries versus its cyanogenic leaves and stems. Every entry in the calculator now carries a "form matters" line where this changes the number.

The oil aisle, sorted in one paragraph

Fish oil and salmon oil deliver EPA and DHA directly, which is the entire point, and are the only oils this calculator doses for joints, skin, kidneys and heart. Flaxseed oil is plant ALA, which dogs convert poorly and cats essentially cannot convert, so it is not a practical omega-3 source for pets. Coconut oil is the wrong fats entirely, with no trials and 120 calories a tablespoon. Hemp seed oil is a pleasant omega-6 salad oil containing no CBD, whatever the bottle design implies. Krill oil is real but weak per capsule. And cod liver oil is actively dangerous at omega-3 doses because the vitamin A and D arrive at toxic levels first, especially in cats. When in doubt: fish oil, dosed on its EPA+DHA, from the calculator above.

The vitamin aisle: what your pet does not need

Dogs and cats synthesise their own vitamin C, so those tablets buy nothing except extra urinary oxalate, which helps build the bladder stones you least want. Vitamin D is the opposite problem: genuinely needed, dangerously easy to overdose — poisoning signs start around 4,000 IU per kilogram, so a single high-strength human capsule can poison a small pet, and supplementing it is a blood-test-and-vet decision, never a shop-shelf one. Multivitamins on a complete commercial diet are money down the drain. The one place vitamins and minerals become essential is the homemade diet: a landmark study found 95 percent of internet home-cooking recipes deficient in at least one nutrient, which is why home-fed pets need a veterinary nutritionist's recipe with its matching balancing supplement, including a formulated calcium plan — about 1 g of calcium per half teaspoon of ground eggshell, but the amount belongs to the recipe, not to guesswork, and never freelanced into a large-breed puppy.

The hard-no list

Four things this page will happily talk you out of. Apple cider vinegar has not one veterinary trial behind any claim — fleas, itch, urinary infections or digestion — and can irritate the stomach, erode enamel and put cats off their water. Colloidal silver treats nothing, per the FDA, and chronic use causes permanent blue-grey skin discolouration and organ damage. Garlic tablets sold as natural flea prevention are three to five times more toxic than onion, oxidise red blood cells into anaemia days later, hit cats hardest, and have never repelled a documented flea; a real parasite preventive costs less than the anaemia workup. And concentrated green tea extract killed dogs in controlled studies, especially on an empty stomach. While we are here: brewer’s yeast flea tablets were put to a controlled test in 1983 and prevented exactly zero fleas, and the garlic half of those combination tablets is the toxic half. The supplement aisle rewards scepticism; that is why every entry in this calculator carries an evidence rating.

Cats are not small dogs

Every feline dose on this page is its own number, not a scaled dog dose. Cats run lower fish oil ceilings with platelet effects at high doses, cannot have cod liver oil chasing omega-3 targets, are ten times more sensitive to alpha-lipoic acid, cannot clear salicylates from willow bark blends, and gain nothing from cranberry in the typical stress-cystitis cat. Meanwhile the supplements with the best feline stories, taurine, B12 and alpha-casozepine, are genuinely useful. If a supplement page you are reading treats "dogs and cats" as one column, close it.

When not to supplement at all

A complete commercial diet already carries the vitamins and minerals; the classic harm is adding calcium to a large-breed puppy's balanced diet, which contributes to developmental bone disease. A sick pet needs a diagnosis before a supplement, because "senior slowing down" is often treatable arthritis pain, and "just a dull coat" is sometimes thyroid disease. And a pet on medication needs the interaction conversation first: fish oil and turmeric alongside anticoagulants, SAM-e alongside serotonergic drugs, and anything sedating alongside behaviour medications. Supplements are the garnish of veterinary care, not the meal.

FAQs

More free ASK A VET™ tools

Building the picture of your pet's health? Try the antihistamine dose calculator, the parasite treatment finder, the vaccination & worming calendar, and the full free tools hub. For health records, reminders and certified vet chat in one place, that is what ASK A VET™ is built for.

Sources & methodology

Every dose in this calculator is anchored to published veterinary sources rather than supplement marketing: peer-reviewed trials (JAVMA, JVIM, JSAP, JFMS, Frontiers in Veterinary Science), the NRC safe upper limits, formulary conventions consistent with Plumb’s and the BSAVA Small Animal Formulary, the Merck Veterinary Manual, university references (Cornell, Colorado State, Tufts, UC Davis), Pet Poison Helpline toxicity data, and manufacturer labels where dosing is label-based (Cosequin, Dasuquin, Denamarin, Zylkene, Anxitane, Crananidin, Cystaid, ProDen PlaqueOff). Key trials cited include Bauer’s JAVMA fish oil reviews, the 2022 Barbeau-Grégoire nutraceutical meta-analysis, Gamble 2018 and McGrath 2019 for CBD, Toresson’s oral B12 work, Ruff 2016 for eggshell membrane, and Bol & Bunnik 2015 for lysine. Evidence tiers are graded on controlled-trial support, not popularity. Where a dose is convention or label rather than trial-derived, the calculator says so in plain sight.

Reviewed by Dr Duncan Houston, University of Sydney BVSc, emergency and general-practice veterinarian and founder of ASK A VET™. Last reviewed August 2026. Doses drawn from published veterinary references including Bauer (JAVMA), the NRC safe upper limits, formulary and label sources, and peer-reviewed trials cited in the text. General guidance only. Confirm every plan with your own vet.