If you have an unspayed female dog, there will come a time when she goes into heat. It can catch first-time owners off guard. But once you know what to expect, it is much easier to keep her comfortable and safe.
Here is what veterinarian Dr. Michael Kearley wants dog owners to understand about the heat cycle.
How Often and How Long
Most female dogs go into heat about twice a year, roughly every six months. That said, breed, age, and individual differences all play a role. Some dogs go into heat only once a year, with as many as 11 months between cycles.
When heat does arrive, it typically lasts 14 to 21 days. During that window, your dog is fertile and can become pregnant.
The Three Phases
A dog’s reproductive cycle has three distinct stages. Knowing what happens in each one helps you recognize where your dog is and what she needs.
- Proestrus — This is the opening phase, lasting about 7 to 10 days on average, though it can range from a few days to four weeks. You will notice a swollen vulva and a bloody discharge. During this phase, she will not allow mating.
- Estrus — This is the fertile stage. It lasts about 9 days on average, but can stretch anywhere from 3 to 21 days. Your dog will accept mating during this time and can become pregnant.
- Anestrus — This is the resting phase, lasting roughly 4 to 5 months. Her reproductive system takes a break before the next cycle begins.
When Does It Start?
Most female dogs have their first heat somewhere between 6 and 24 months of age. Breed size plays a big role in the timing. Even though a dog can technically become pregnant during her very first heat, breeding at that stage is generally not recommended because she has not yet reached full physical maturity.
Signs Your Dog Is in Heat
Your dog’s body and behavior will both signal that something has changed. Here is what to watch for:
Physical signs:
- Swollen vulva
- Bloody or pink vaginal discharge
- Swollen nipples
- Increased urination
Behavioral signs:
- Restlessness
- Decreased appetite
- Excessive licking of the vulva
- Becoming more affectionate or more aggressive than usual
- Increased attention from male dogs
Do Dogs Ever Stop Going Into Heat?
Unlike people, dogs do not go through menopause. An unspayed female dog can continue going into heat and can become pregnant throughout her entire life. Her cycles may slow down or space out as she ages, and that is considered normal.
However, if her cycles stop completely, a vet visit is a good idea, since this can sometimes point to an underlying medical or metabolic condition.
It is also worth knowing that female dogs older than 8 years face a higher risk of developing pyometra, a serious uterine infection. And while older dogs can still become pregnant, breeding senior females is generally not recommended because they tend to have smaller litters, higher puppy loss, and a greater risk of difficult labor.
Keeping Her Comfortable and Safe
When your dog is in heat, your main goals are preventing an unplanned pregnancy and keeping her at ease. A few practical steps make a real difference:
- Use a dog diaper to contain discharge and reduce mess around the house. Choose one that is absorbent and leakproof, and change it every 3 to 4 hours.
- If you have male and female dogs in the same home, keep them fully separated using crates, gates, and closed doors. Dog diapers alone are not a reliable way to prevent pregnancy.
- Avoid dog parks and places where she might encounter intact male dogs.
- Keep her on a leash during all walks.
Even dogs in fenced yards can find a way to mate, so close supervision is essential during the heat cycle.
Your vet is your best partner in deciding what is right for your dog and your situation. A quick call or visit can give you a clear plan and real peace of mind.