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A Guide To Female Dog Heat Cycles

Written by Ella White


dog lying in bed

Like humans and all other mammals, dogs experience a cycle where they are most receptive to mating. Known as estrus, or ‘heat’, female dogs begin to experience this cycle from the age of six months old, and it will continue for the rest of their life unless medically prevented.

Here we’ll explain everything you need to know about heat cycles in female dogs, from the signs that your dog is in heat, to how long the cycle lasts, to looking after your dog during the estrus cycle.

When Does Heat Start?

When female dogs start going into heat depends on the size of the breed. Though the average age for the first cycle is about six months, smaller breeds can begin as young as four months old. Whereas giant breeds might not experience their first heat cycle until they’re 18 to 24 months old. 

Though the estrus cycle indicates that a dog is able to get pregnant, it’s strongly advised that you do not allow female dogs to mate in their first or second cycles. This is because the dog hasn’t yet reached full maturity, and therefore their eggs are also not fully matured.

Waiting until at least the third estrus cycle will ensure your best chances of a healthy pregnancy. And if you do intend to breed your dog, get confirmation from your vet that they are mature and healthy enough before they get pregnant.

How Often Do Dogs Go Into Heat?

How often a dog will experience her estrus cycle will depend on their age, size, and breed. In young, healthy dogs that have not been spayed, this should happen twice a year at six month intervals. The heat cycle lasts 18 days.

Once a dog’s estrus cycle has started, it can take up to 18 months to become regular. Some owners might want to keep a record of their dog’s early cycles. Small dogs can go into heat more frequently, while giant breeds sometimes only go into heat once every 12 to 18 months.

If you notice that your dog’s heat cycles are not consistent, consult your vet. The frequency will slow down in older dogs, but as long as they experience their heat seasons they can still get pregnant. This is because dogs don’t go through a menopause like humans so they’ll experience the estrus cycle throughout their entire lives. 

For this reason, most dog owners that do not intend to breed their pets choose to spay their female dogs. It prevents the heat cycle from happening, means there will be no unwanted pregnancies, and is even thought to reduce the risk of some conditions and diseases including mammary cancer.

What Are The Signs Of Estrus In Dogs?

There are a number of signs to look out for that indicate your dog is in heat aside from bleeding, which only happens for about half the cycle – or 7 to 10 days. These include:

  • Red, swollen vulva
  • Bloody discharge
  • More frequent urination
  • Nervousness
  • Increased alertness
  • Increased interested in or friendliness with other dogs
  • Seeking out male dogs
  • Mounting or humping objects and animals
  • Tail turned to the side

The amount a dog bleeds will depend on their size, with larger dogs usually bleeding more than smaller dogs. Being in heat can make dogs nervous and fidgety, but while they’re bleeding they’re not in pain and won’t experience menstrual cramps the same way humans can. If you think the heat cycle is causing your dog pain, take them to the vet.

Dogs that groom themselves regularly often clean up their own blood, so you won’t find any spotting around the house. However, many dog owners invest in extra blankets or hygiene pants for extra peace of mind.

How Long Is Each Cycle?

The heat cycle lasts from 2-4 weeks, with some female dogs being receptive to males for the full cycle and others becoming more receptive later in the cycle. Dogs can get pregnant throughout the cycle, although their fertility is at its peak about 10 days after the cycle begins and lasts five days. When your dog’s bleeding and discharge has stopped and their vulva is no longer swollen, the cycle has ended.

The estrus cycle has four stages:

  1. Proestrus, which lasts 7 to 10 days. The bleeding begins and the vulva swells, but the dog is not yet ready to mate.
  2. Estrus, which lasts 5 to 10 days. The bleeding may reduce or stop completely, and the dog is ready to mate.
  3. Diestrus, which lasts 10 to 140 days. This is when a dog is either pregnant, or in a period of rest.
  4. Anestrus, which lasts 6 months. This is the downtime before the next heat cycle begins.

Caring For Your Dog In Heat

Female dogs in heat can be hormonal and nervous, and will often require extra care. Give her extra attention and try to keep her entertained to distract her from the discomfort. But bear in mind that a female dog in heat will attract a lot of attention from male dogs. 

For this reason, a female dog in heat should not be let off leash and shouldn’t be walked near other dogs. Where possible, keep her away from unneutered male dogs. At home, build them a comfy space to nap using towels and blankets you don’t mind her bleeding onto. Some owners might prefer to keep bleeding dogs in a specific area of the house to prevent spotting elsewhere.