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❤️ Vet’s 2025 Guide to What to Expect When Your Dog Is in Season: The Estrus Cycle Explained 🐶
By Dr Duncan Houston, BVSc
Whether you’re planning to breed or simply missed the window to spay, having a female dog “in season” can be a confusing and stressful experience. Her first heat—also known as estrus—can bring changes in behavior, appearance, and even her social life. 😅
This comprehensive 2025 guide walks you through what to expect at each stage of the canine estrous cycle, how to keep her safe, and why timely spaying matters. 🐾
🩸 What Does “In Season” Mean?
Being “in season” refers to your dog’s reproductive cycle—similar to menstruation in humans, but with important differences. Dogs don’t bleed monthly. Instead, estrus typically occurs twice a year, or every 6–7 months. 🗓️
The entire cycle consists of four phases:
- Proestrus – Getting ready (beginning)
- Estrus – Receptive and fertile (middle)
- Diestrus – Winding down (end)
- Anestrus – Resting phase (pause before the next cycle)
📅 Age of First Estrus
- 🧒 Small breeds: Around 6 months old
- 🦮 Large breeds: May not cycle until 9–12 months old
Tip: Plan spay surgery before 6 months if you want to avoid the first heat. Call your vet early to schedule! 📞
1️⃣ Proestrus (Beginning Phase)
What You’ll Notice:
- 🩸 Bloody vaginal discharge
- 🔴 Swollen vulva
- 🐕 Frequent urination
- 🐾 Attracting males but not receptive
- 💋 More clingy or affectionate—or grumpy
- 🗣️ Increased vocalizing or whining
Discharge may be heavy and bright red. She may lick herself often or leave spots around the house. Be prepared for cleanup—puppy pads or washable diapers can help (though diapers won’t stop determined males!). 🧽
Duration: Typically 7–10 days but may last up to 4 weeks.
2️⃣ Estrus (Fertile Phase)
What You’ll Notice:
- 🌸 Lighter discharge
- ❤️ Receptive to males—will turn and “flag” tail
- 🚪 Wants to go outside more often
- 🐶 May try to escape the yard or jump fences
This is when ovulation occurs—your dog is fertile. Male dogs can detect pheromones from long distances, so don’t be surprised if neighborhood dogs appear. Keep her indoors, supervised, and never off-leash—even in a fenced yard. 🔒
Duration: 7–9 days on average, but can last up to 21 days.
3️⃣ Diestrus (End Phase)
What You’ll Notice:
- 😌 She’s no longer interested in males
- 🩺 Discharge stops or becomes minimal
- 🧘 Vulva slowly returns to normal
If she was bred, pregnancy begins now. Canine gestation is around 58–63 days. If she wasn’t bred, hormone levels slowly normalize. You may notice little behavioral change, but her body is going through a lot. 🧬
Duration: About 60 days (whether pregnant or not).
4️⃣ Anestrus (Rest Period)
The calm before the next storm. 😌 This is the downtime between cycles. No discharge, no hormonal swings—just peace and normal behavior. 🌼
Duration: Around 4–6 months, depending on breed and individual cycle.
⚠️ Dangers of Estrus
- 🐶 Unwanted pregnancy
- 🧬 Increased risk of mammary tumors (especially after multiple heats)
- 🦠 Pyometra (life-threatening uterine infection in unspayed dogs)
Spaying before the first or second heat significantly reduces these risks. 💉
💡 Managing a Dog in Heat
- 🏠 Keep her indoors
- 🐾 Use diapers or limit access to carpeted areas
- 🚫 Avoid dog parks and social outings
- 🔒 Double-check gates and fences
- 🧼 Clean bedding frequently
What NOT to Do:
- ❌ Don’t let her roam—even with a fence
- ❌ Don’t assume diapers will prevent mating
- ❌ Don’t delay a vet visit if you suspect she’s pregnant
🧠 Signs She May Be Pregnant
- 🐕🦺 Behavior changes
- 🍽️ Appetite fluctuations
- 🩺 Abdominal enlargement
If you suspect pregnancy, schedule a vet visit ASAP. Early detection can help you make informed decisions. 📋
📱 Ask A Vet Can Help
Worried about behavior changes or discharge? Need to know when to spay or how to prevent pregnancy? Visit AskAVet.com for:
- 📅 Spay timing advice
- 📸 Review of photos if you’re unsure about swelling or discharge
- 💬 Behavior management support during heat
📲 Download the Ask A Vet App
Track her cycle, get alerts for the fertile window, and chat with a licensed vet when questions arise. 🐶📱
🎯 Final Thoughts
A dog in season needs protection, guidance, and supervision. Whether you plan to spay or not, understanding her cycle helps you safeguard her health and prevent surprises. 🩺
From behavior to bleeding, you’ve got the knowledge—and we’re here if you need backup. 🐕💬
Because caring for her through every cycle is part of being her person. ❤️🐾
