How Often Do Heats Occur in Large Breed Dogs and What to Expect the First Time

If you are raising a large breed puppy, you have probably wondered when that first heat will arrive and how often it will happen after that. It is a big milestone, both for her and for you. Large breeds like Labrador Retrievers, German Shepherds, Golden Retrievers, and especially giant breeds such as Saint Bernards or Irish Wolfhounds follow a different reproductive timeline than their smaller cousins. The short answer is: most large breeds have their first heat between 12 and 24 months, and then they cycle every 6 to 12 months, with many giant breeds only cycling once per year. But let us walk through the details so you know exactly what to watch for and how to plan.

When Does a Large Breed Dog Have Her First Heat?

For large and giant breeds, the first heat (called the estrus cycle) arrives later than for small breeds. A Chihuahua might start as early as 6 months, but a Great Dane or Bernese Mountain Dog often waits until 18 to 24 months. Why the delay? Large dogs take longer to reach physical and skeletal maturity. Their bodies need more time to grow before they are ready to support a pregnancy. If your large breed female has not shown signs of heat by 24 months, it is a good idea to check with your vet. Some lines, especially in giant breeds, can start as late as 30 months and still be normal. Watch for common signs: a swollen vulva, a bloody discharge, increased urination, and changes in behavior like clinginess or restlessness. Some dogs also become more interested in male dogs even before bleeding starts.

How Often Do Large Breeds Go Into Heat After the First One?

After the first heat, most large breed dogs enter a regular cycle that occurs every 6 to 12 months. The average is about once every 8 months. However, giant breeds like the Newfoundland or the Scottish Deerhound often fall on the longer end of that range, sometimes going 12 to 14 months between cycles. This is very different from small breeds, which can cycle every 4 to 6 months. The reason is partly hormonal and partly evolutionary — larger bodies take longer to reset the reproductive system. If your large breed dog seems to be cycling more often than every 6 months, or less often than every 14 months, mention it to your vet. Irregular cycles can sometimes signal thyroid issues or ovarian cysts, but they are often just normal variation.

What Are the Four Stages of the Heat Cycle in Large Breeds?

Understanding the stages helps you predict when she is fertile and when the bleeding will stop. The cycle has four parts:

• Proestrus: This is the start. You will see swelling and bloody discharge. She will attract males but will not allow mating. This lasts about 7 to 10 days in large breeds, sometimes longer.
• Estrus: This is the fertile window. The discharge becomes lighter pink or straw-colored, and she will stand for a male. This lasts 5 to 9 days. If you want to avoid pregnancy, keep her away from intact males during this time.
• Diestrus: After estrus, her body either becomes pregnant or enters a resting phase. Hormones like progesterone stay high for about 2 months, even if she is not pregnant. You may see false pregnancy symptoms like nesting or milk production.
• Anestrus: This is the long break between cycles. For large breeds, this can last 4 to 8 months. It is a quiet time with no visible signs of heat.

Tracking these stages on a calendar helps you know when the next heat is due. For example, if her diestrus and anestrus together last 7 months, you can expect her next proestrus about 7 months after the last one ended.

“The first heat is a sign of maturity, not a signal to breed. Give her body the time it needs to fully develop.”

Should You Spay Before or After the First Heat?

This is a big decision for large breed owners. Spaying before the first heat greatly reduces the risk of mammary cancer and eliminates the chance of pyometra (a serious uterine infection). However, for large and giant breeds, there is growing evidence that early spaying (before 12 months) may increase the risk of joint disorders like hip dysplasia and cruciate ligament tears. Many veterinarians now recommend waiting until after the first heat, or even until 18 to 24 months for giant breeds, to allow the bones to close properly. You should talk with your vet about your specific dog’s breed, lifestyle, and health history. There is no one-size-fits-all answer, but waiting until after the first heat is a common middle ground. For more details on timing, you can read our guide on spaying large breed dogs after their first heat.

How Does the First Heat Affect Behavior and Health?

You might notice your large breed puppy acting differently during her first heat. She may become more affectionate, or she might seem grumpy and want more space. Some dogs lose their appetite for a day or two. It is also common for them to urinate more frequently, sometimes even inside the house, as they mark territory with scent. Keep her on a leash during walks because male dogs can smell her from a mile away. If you have an intact male in the house, you will need to separate them completely for about three weeks. Health-wise, the first heat is a normal process, but watch for signs of illness like a foul-smelling discharge, excessive thirst, or lethargy. These could indicate a uterine infection, which needs immediate veterinary attention. For a deeper look at behavior changes, check our article on heat cycle behavior changes in large breed dogs.

What About False Pregnancies and Other Concerns?

False pregnancy, or pseudopregnancy, is very common after the first heat in large breeds. She might start carrying toys around, make a nest, or even produce a small amount of milk. This is caused by the natural drop in progesterone after diestrus. It usually resolves on its own within two to three weeks. Do not punish her for it, and avoid stimulating her nipples, as that can encourage more milk production. If the symptoms are severe or last longer than a month, your vet can help. Another concern is the risk of accidental pregnancy. Large breed puppies are adorable, but an unplanned litter can be expensive and stressful. Keep her confined and supervised during the entire fertile period (about 10 to 14 days of the estrus stage). For more on preventing unwanted litters, see our guide on preventing accidental pregnancy in large breed dogs.