Updated - Jun 29th, 2022
It’s spring, which means the birds and the bees are out and about – but hopefully, not your dog, unless you want to deal with a litter of puppies you didn’t expect. Thankfully that’s only a risk when your dog is in heat, and they’re not in heat all the time.
When do dogs go into heat?
Most dogs enter estrus – the scientific term for heat – twice a year. In the wild, this is the time when they’d be pairing up and mating. The cycle starts when dogs enter puberty, around six months of age, but this depends on your dog’s breed. Some dogs, particularly larger dogs, experience their first heat cycle later and have their subsequent cycles less frequently, and other dogs (generally smaller breeds) begin their first cycle sooner and experience estrus multiple times per year.
In general, heat lasts around two to three weeks and occurs twice a year, after your dog reaches sexual maturity and before she reaches menopause. If your dog is spayed, she won’t enter heat.
The first stage: Proestrus
Each stage of a dog’s heat cycle lasts between one week and ten days. The first stage, proestrus, is the buildup: your dog starts to show the signs but isn’t ready to mate yet. The signs of a dog in heat are simple.
Your dog’s vulva will appear swollen and red compared to its normal size and color. Your dog will also start to urinate more – and their urine may contain blood. The bleeding and vaginal discharge usually last around a week before it lessens.
To prevent mess and make your pooch more comfortable, consider getting them a doggy diaper.
The second stage: Estrus
In the second stage, your dog starts actively seeking a mate. You’ll see less discharge in your dog’s urine. The swelling of the vulva will slightly lessen. At this point, you’ll notice certain behavioral changes. Your dog may seem anxious or restless, keeping their tail bent at odd angles, and might even engage in mounting and humping.
Be sure to keep your dog away from other dogs, especially male dogs, during this period. Instead, offer games and toys to distract her and create a vent for her unspent energy. It’s worth noting that a doggy diaper won’t prevent breeding – it only helps with discharge – so don’t think it will provide a fool-proof barrier.
The third and fourth stages: Diestrus and Anestrus
After this stage, if your dog hasn’t been impregnated, she will rest for another week – the comedown, or diestrus – as their estrus comes to an end. Swelling will decrease and eventually vanish. In this stage, your dog may become lethargic or seem depressed. Your treatment will have to change accordingly: instead of trying to find outlets for her energy, you’ll want to create a comforting space for recovery.
What happens next is called anestrus: the period between heat cycles. Your dog’s behavior will return to normal. This will last around six months until the next heat begins – however, again, this depends on their breed.
If your dog seems to be in pain at any point during this cycle, consult your vet. She may be suffering from a uterine infection or other estrus-related difficulty. Extremely long periods of estrus may be the result of an underlying condition such as a cyst or a tumor: if your dog appears to be in estrus for weeks at a time, talk to your veterinarian.
Medical care for dogs in heat
It bears repeating: if your dog is spayed, she won’t enter heat. Spaying or neutering your dog is essential for preventing unwanted pregnancies and reducing aggressive behavior. Spaying also reduces the risk of certain cancers, and as a result, spayed dogs have a longer life expectancy. An unspayed female faces more health risks. If your dog is only intended as a companion, you should definitely get her spayed.
There’s a debate, however, over whether dogs should be spayed before their first heat. Getting spayed early might eliminate the risk of ovarian cancers, but it might increase the risk of other diseases – particularly diseases related to bone growth. There’s still a lot of debate in the veterinary field about this issue. Most vets agree, however, that the earlier the better when it comes to spaying. Your decision will have to depend on the particular circumstances of your dog’s health.
At the end of the day, if you have concerns about your dog’s health or behavior, you should always talk to your vet. Make sure that your vet becomes familiar enough with your dog to recognize her particular behaviors and symptoms. Learn the signs that your dog is entering heat so you can be ready to support her throughout her cycle.