We would expect our adorable canines to experience their first heat at about the 6 months mark and certainly, some dog breeds do take longer or shorter periods. However, it’s really disturbing when a 2-year-old female dog is yet to come to heat. What could possibly have gone wrong?

Large dog breeds can also take as long as 2 years to come into heat. Some dogs go through silent heat in which regular signs of the heat cycle are hidden. Irregular cycles or absence of heat periods can also occur due to hypothyroidism, malnutrition, ovarian disorders, and drug Inhibition.

Visit your local vet to run the necessary blood tests or carry out diagnostic imaging to rule out any underlying health issues.

Remember, a spayed bitch can no longer go into heat because the ovaries which produce estrogen, the hormone responsible for normal reproductive functions, is removed.

We’ll break down the reasons why the canine heat periods may be delayed or not noticed, and discuss ways to make dogs go into heat faster.

Why Is My Dog Not Coming Into Heat

The possible reasons why your dog is not coming into heat when expected include but are not limited to:

1. Breed Variations

Breed differences can determine whether dogs go through estrus early enough. Small dog breeds tend to have shorter cycles and giant and large dog breeds can have very late cycles of even up to 2 years.

This is because it takes a longer time for the reproductive system of large dogs to fully develop. Hence, if a large dog is experiencing what seems like a delayed heat, especially in their first heat, it may be normal and does not necessarily mean they have underlying health problems.

However, it is recommended to test your large dog at the 24th to 30th month of its life if they are yet to come into heat. Small or medium-sized dogs should be tested between 6 to 12 months.

2. Silent Heat

Dogs sometimes experience silent heat, especially in their first few cycles. In this condition, dogs come into heat without exhibiting the normal signs of heat like swelling of the vulva and vaginal discharge. These signs are often too negligible to be observed by most dog owners or even breeders.

Even the common behavioral changes like being receptive to males, tail flagging, frequent urination, excessive grooming, and restlessness may not be evident in dogs experiencing silent heat. Vets can confirm if your dog is in silent heat by checking the progesterone level and microscopically viewing the vaginal preparation of the dog.

3. Malnutrition

Malnutrition can cause irregular cycles in dogs in which your dog’s heat may be delayed. This can happen if you do not have a fixed feeding routine for your dog or often give your dog low-quality food with an inadequate amount of protein, vitamins, and minerals.

Malnourished dogs usually have lower metabolic rates. Hence, the production of the hormones that control the heat cycle such as progesterone, estrogen, LH, and FSH, may be affected.

4. Thyroid Dysfunction

Just like malnutrition, hypothyroidism can also result in a reduction of the metabolic rate in dogs. Lymphocytic thyroiditis is responsible for about half of the cases of hypothyroidism in dogs. Depending on the severity of the hypothyroidism, the affected dog can have irregular cycles or lack of heat periods.

Large and medium dog breeds are at greater risk of developing hypothyroidism. This is also true for certain dog breeds like Irish Setter, Golden retriever, cocker spaniel, Dachshund, Doberman Pinscher, Miniature Schnauzer, and Boxer.

Symptoms that highly suggest the presence of low thyroid hormones in dogs include excessive shedding, loss and thinning of hair, skin and ear infections, weight gain, lethargy, muscle wasting, bradycardia, and hypothermia.

It Is not advisable to breed hypothyroid dogs because of the high risk of spontaneous abortion and stillbirths. While the symptoms of hypothyroidism can be clinically improved by the administration of levothyroxine, the condition is not curable.

5. Ovarian Disorders

The ovaries contain the female reproductive gamete known as the egg or ovum and are responsible for the production of progesterone and estrogen, which controls the heat cycle in dogs. Ovarian disorders are rather rare but can affect the functions of ovaries. Ovarian hypoplasia, cyst, and neoplasia are the most common disorders.

Ovarian hypoplasia is a congenital abnormality that can occur in dogs in which the ovaries are underdeveloped due to the absence of germ cells making them unable to carry out their normal functions of producing eggs and female sex hormones. Hence, the affected dog cannot come into heat.

Ovarian cysts and neoplasia can also affect the reproductive health of your dog. An ovarian cyst is a fluid-filled sac of regular cells in the ovary or on its surface. It is usually benign but can develop to become a malignant tumor. On the other hand, in ovarian tumors, there is an excessive and uncontrolled proliferation of the cells of the ovary.

A blood test can be carried out to rule out other potential causes of absent or missing heat in dogs like thyroid dysfunction, malnutrition, and drug Inhibition. Ultrasound, x-ray, and karyotype genetic tests may also help to confirm the diagnosis.

6. Drug Inhibition

If your dog has a history of the use of any drug that can interfere with the heat cycle, then drug-related inhibition may be a culprit.

Drugs such as progestin and androgen can reduce the onset of heat cycles in dogs. The use of agents like glucocorticoids may suppress GnRH, thereby decreasing reproductive activities. GnRH agonist also induces the inhibition of heat cycles in dogs.

Most drug-related cases of heat cycle Inhibition can not be reversed but the prolonged effects of these drugs diminish with time.

When To Visit Your Vet

It is important to always keep an eye on your dog so that you can notice various physical and behavioral changes dogs exhibit when they are in heat. Progesterone blood test and vaginal cytology once a week are recommended to check if your dog is in silent heat and to know the best time for your to mate.

As a general rule, small and medium-sized dogs should be checked between 6 to 12 months of their life if they are yet to show signs of heat. Large and giant dog breeds can be checked at or after the 2-year mark if he’s not been in heat.

Diagnosis of the underlying condition begins with history taking and physical examination after which your vet runs multiple tests to rule out the possibility of other conditions affecting the heat cycle of your dog.

Lab tests such as complete blood count, urinalysis, and biochemical panel are done to measure the levels of important hormones, and for the presence of existing drugs causing reproductive inhibition. Abdominal ultrasound, MRI, or X-ray may be useful in the diagnosis of ovarian disorders.

Also Read: How Soon Can A Dog Get Pregnant After Giving Birth (Explained!)

Ways To Make Dogs Come Into Heat Faster

Though heat cycles are a natural part of a dog’s life they can be affected by environmental factors. The good news is that this can be used to your advantage if you want your dog to come into heat faster.

Bear in mind that breeding dogs in their first or second heat is discouraged because at these ages your dog is too young to handle pregnancies and the risk of possible complications is higher.

Feeding your dog a high-quality diet is important for the production of reproduction of reproductive hormones. Regular exercise is encouraged for the general health of your pooch.

Furthermore, when female pups are surrounded by cycling female, their heat cycle tend to begin faster. Also, make sure your dog is free of anxiety and stress as these conditions can suppress various hormones responsible for heat cycles.

A common drug known as PG 600 can also be used to stimulate heat in dogs but using this drug is painful and comes with serious health risks for your dog.

How Late Can A Dog Have First Heat

Small dogs usually experience their first heat in about 3 months but it can be applied s late as 6 months when delayed. Medium-sized dogs can experience their first heat as late as 9 months. However, large and giant dog breeds can go up to 2 years but usually experience heat at about the 12 months mark.

If you are worried about your dog not coming into heat, it is best to visit the vet for weekly progesterone tests and vaginal cytology so you can tell for sure when your dog goes into heat. You can also check for the presence of any health problems delaying or preventing your dog’s heat.

Final Thoughts: 2-Year-Old Dog Never Been In Heat

Large dogs can experience their first heat in as long as 2 years but this does not happen all the time. Small or medium-sized dog breeds never live for that long without going into heat except in cases where underlying health issues are present.

To confirm whether your dog is missing heat cycles or just experiencing silent heat, you will have to perform a blood test and other investigative procedures like ultrasonoscopy and X-ray.

Various conditions can delay or suppress heat cycles. From malnutrition, hypothyroidism, ovarian hypoplasia and tumors, and drug inhibition. These conditions also have a negative effect on the entire well-being of your dog. Spaying is recommended in dogs with thyroid and ovarian issues to prevent unfavorable progression.