Dogs in Heat: Signs, Safe Management and When to Call the Vet
In this article
By Dr Duncan Houston
A first heat can bring spotting, a swollen vulva and a dog who seems unusually distracted. Knowing what changes are expected helps you keep her comfortable, prevent an unintended mating and recognise illness that should not be dismissed as hormones.
Quick Answer
A dog's heat is the part of her reproductive cycle when she attracts males and may become pregnant. Timing varies considerably, so keep her securely separated from entire male dogs throughout the season rather than relying on bleeding or a calendar. Marked illness, foul discharge, vomiting or increased thirst require veterinary advice, particularly in the weeks after a heat.
When does the first heat happen?
According to Cornell's guide to dog heat cycles, the first season can begin between about six and 24 months, with smaller breeds generally starting earlier. Many dogs cycle roughly twice yearly, but individual and breed differences are substantial.
Visible signs commonly last a few weeks. Some dogs clean away most discharge, making the start easy to miss. Record dates and changes, then ask your vet about unusually prolonged signs, a major change in pattern, or uncertainty about whether your dog is in season.
What the cycle stages mean
| Stage | Typical changes | Practical implication |
|---|---|---|
| Proestrus | The vulva enlarges; bloody discharge and male interest often begin. | Start secure separation immediately. |
| Oestrus | The female may accept mating; discharge may become lighter. | Less bleeding does not mean pregnancy risk has ended. |
| Diestrus | The reproductive tract remains under progesterone influence after the receptive period. | Monitor for illness and false-pregnancy signs. |
| Anoestrus | A quieter interval occurs before the next cycle. | Discuss longer-term reproductive care with your vet. |
These stages do not follow a precise home timetable. Veterinary hormone testing and examination can help assess reproductive status when needed; coat colour, tail position or the day bleeding started cannot reliably identify a safe mating-free window. The Merck Veterinary Manual's reproduction guidance explains why breeding timing requires more than counting days.
Prevent mating with a practical household plan
- Walk on a secure lead in quieter places and avoid dog parks or group daycare.
- Supervise garden visits. A fence does not make an unattended dog safe from mating or escape.
- Separate entire males and females with secure physical barriers; a single baby gate may be inadequate.
- Tell every household member, walker and boarding provider that she is in heat.
- Arrange genuinely separate accommodation if reliable separation at home is not possible.
Dog pants can help protect furniture, but they are not contraception. Change them often, check the skin and remove them for toileting. Keep bedding washable and offer normal opportunities to rest, sniff and interact without crowding her.
If mating occurs, contact your vet promptly even if you are unsure whether pregnancy is possible. If the dogs are tied, keep the situation calm and do not pull them apart, which can cause injury. Do not use human emergency contraceptives or home remedies.
Which changes need medical attention?
Some restlessness and altered social behaviour can accompany a season. Substantial pain, fever, pronounced lethargy, repeated vomiting or refusing food are not signs to simply wait out. Arrange assessment for unexpectedly heavy bleeding, offensive discharge or repeated straining to urinate.
Pyometra is a serious uterine infection that often develops one to two months after heat. Warning signs include increased drinking or urination, poor appetite, vomiting, weakness and a painful or enlarged abdomen. Discharge may be absent when the cervix is closed. Seek urgent veterinary care rather than waiting for discharge to appear.
Collapse, breathing difficulty, pale gums or severe weakness warrant emergency care. Tell the clinic when the last season occurred and whether mating was possible.
Planning ahead and avoiding common mistakes
Discuss desexing with your vet based on your dog's health, breed, age and circumstances. Surgery that removes the ovaries prevents future heats; the best timing around a current season is an individual decision. Tell the clinic she is in heat before an appointment, but do not postpone necessary medical care.
Dogs do not need a litter for emotional wellbeing. Breeding requires preparation, relevant health screening and plans for pregnancy, birth and puppy care. Avoid treating it as an inevitable next step after a first season.
Frequently Asked Questions
Can she become pregnant on her first heat?
Yes. A first season is not a safe exception, even when the dog still looks like a puppy.
Is she safe once the bleeding stops?
No. Discharge can decrease while pregnancy remains possible. Continue precautions and ask your vet when the season appears to have ended.
Can she still exercise?
Usually she can have comfortable lead walks and supervised enrichment. Avoid encounters with entire males and adapt activity if she seems uncomfortable.
Why is she nesting after her season?
Hormonal changes can cause false pregnancy, including nesting and mammary changes. Arrange veterinary advice, especially if she is distressed or unwell; do not assume every post-heat change is harmless.
A calm routine and reliable separation make a heat easier to manage. For help preparing questions about cycles, desexing or changes you have noticed, contact ASK A VET™; an unwell dog needs prompt examination by your local veterinarian.
