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Why Has My Dog Not Come Into Season Yet?

↯ Key takeaway points

  • Heat cycle irregularities are common in female dogs and can be caused by various factors such as age, breed, and underlying health conditions.
  • Toy breeds mature quickly and may come into heat as young as four months old, while large and giant breeds may not have their first heat until they are older.
  • Hypothyroidism, an underactive thyroid condition, can cause irregular heat cycles and other symptoms such as weight gain and lethargy.
  • Silent heat, also known as sub-estrus, is when a bitch ovulates without showing external signs of heat like vaginal discharge or interest in male dogs.
  • Other factors that can affect a dog's heat cycles include malnutrition, ovarian tumors, and certain types of abnormal heat cycles such as absent, split, or prolonged heats.
Written by Jay
BsC (Hons) Animal Behaviour & Welfare graduate with a passion for advocating for misunderstood animals.
Practicing small pets and equine veterinarian and junior teaching assistant in Veterinary Medicine.
Published on
Thursday 12 November 2020
Last updated on
Friday 7 July 2023
why has my dog not come into season yet
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Waiting for your bitch’s first estrus cycle can be an exciting but nerve-wracking time. Unfortunately, heat cycle irregularities are a common problem in female dogs and many breeders encounter them. New breeders especially find themselves asking, “why has my dog not come into season yet?”

There are several possible reasons why a bitch has not come into season yet. These reasons may be as simple as her age, or as serious as an underlying health condition. No matter what the cause is, it’s best to monitor your dog’s estrus cycles closely to be sure that her reproductive system is working correctly.

Why Has My Dog Not Come Into Season?

There are several possible reasons why your dog has not come into season yet. While some causes are simply down to age, others are due to underlying health problems such as hypothyroidism.

Breed Differences

On average, a dog reaches sexual maturity at six months old. However, this varies by breed. Toy breeds such as Chihuahuas, Papillons, and Miniature Pinschers can come into heat as young as four months old. This is because toy breeds mature rapidly and need less time to grow than other breeds. Despite maturing quickly, many breeders will hold back toy breed puppies until they are 12 weeks old instead of 8 weeks due to their fragility.

Similarly, small breeds like Cairn Terriers, Border Terriers, and Brussels Griffons tend to come into heat at six months old. Large breeds like Akitas, American Foxhounds, and Labrador Retrievers might not come into their first heat until they are 12 months old. Giant dog breeds like Great Danes, Newfoundlands, and Irish Wolfhounds typically come into their first heat much later at two years old.


Hypothyroidism, also called underactive thyroid, is a condition in which the thyroid gland does not produce enough hormones. Your dog’s thyroid gland produces hormones responsible for their metabolism. So, if your dog has hypothyroidism, their metabolism slows down significantly.

When your dog’s metabolism slows down every organ in the body is affected. Your dog might show the following symptoms: getting cold easily, gaining weight, lethargy, dry and dull coat, hair loss, recurrent ear infections, slow heart rate, and high blood cholesterol. Rarer symptoms include thickening of the facial skin, lameness, infertility, and fatty deposits in the corneas of the eyes. Finally, the most relevant symptom to discuss is a lack of heat periods, miscarriages, and abortion of litters.

Hypothyroidism is manageable but not curable. Most vets treat hypothyroidism by orally administrating a thyroid replacement hormone, most commonly levothyroxine. This treatment is given for the rest of your pet’s life. After one month of treatment, your vet will take a blood sample to check that your dog’s hormone levels are improving. From here, your dog’s thyroid hormone levels are typically tested every six months. You can also feed your dog with the best dog food for hypothyroidism.

hypothyroidism in dogs
Hypothyroidism is having an underactive thyroid.

Your Dog Might Have Had a Silent Heat

Silent heat, or sub-estrus, is defined as the maintenance of ovarian function without external signs of heat. This means that your bitch ovulates without any vaginal discharge, vulvar edema, or interest in male dogs. In young bitches of smaller breeds, silent heats can occur for several cycles before the first normal estrus. If silent heat is suspected, your vet might recommend testing your pet’s serum progesterone levels. This can help to verify that your bitch’s ovaries are functioning.

She Did But You Didn’t Notice

In some cases, owners might miss their bitch’s heat. For example, it can be difficult to notice vaginal discharge if your bitch frequently licks herself clean (or if you groom her often). The swelling of the vulva may also be minimal and go unnoticed.

Similarly, it’s easy for a new owner to misinterpret or miss their dog’s heat cycle. Signs of being in heat include:

  • a swollen vulva,
  • bloody discharge from the vagina,
  • licking the genital area,
  • nervous behavior, and
  • urinating more frequently.

Every bitch is different, and her heat cycle may not be as obvious as another dog’s cycle. As you get to know your new dog, you will also get to know what her heat cycles look like if she is not spayed.


While malnutrition can arise due to a lack of food, there are other causes for it that may be less obvious. Other causes include providing the incorrect food for your pet’s life stage, and digestive diseases that prevent the absorption of nutrients. Malnutrition in any form can cause irregular heat cycles. Similarly to humans, malnutrition affects how the hypothalamus and pituitary gland functions.

Both the hypothalamus and pituitary gland are involved in your bitch’s estrus cycle. Gonadotropin-releasing hormone (GnRH) is released from your dog’s hypothalamus. GnRH is necessary for the release of follicle-stimulating hormone and luteinizing hormone. These hormones are necessary for kickstarting ovulation. Without ovulation, your bitch cannot go into estrus and consequently cannot breed. Be sure to check with your vet if you have any questions or concerns about your dog’s diet!

Tumor on the Ovaries

Ovarian tumors are rare in dogs, comprising 0.5 to 1.2 percent of all canine tumors. The risk of ovarian tumors increases with age, with the median age at diagnosis sitting at 10 years. According to some studies, English Bulldogs, Boston Terriers, German Shepherds, and Poodles are at a higher risk of ovarian tumors. However, other studies refute this claim.

Diagnosing ovarian tumors can be difficult because the clinical symptoms are often non-specific. In fact, symptoms may only manifest by the time the tumor is very large. Major clinical findings include irregular heat cycles, vaginal discharge, lack of appetite, weight loss, and thinning of the coat. In severe cases, fluid may build in the abdomen, causing a rounded appearance. If you suspect your bitch is suffering from ovarian tumors, a vet will need to conduct several tests. Through a physical examination, your vet may identify a noticeable mass in the abdomen if the tumor is large enough. Your vet will likely take a blood sample.

ovarian tumors in dogs
Ovarian tumors are more common in older dogs.

Types of Abnormal Heat Cycles in Dogs

There are four main types of abnormal heat cycles in female dogs: absent, silent, split, and prolonged. If your dog has not come into heat yet, it’s possible that one of these cycle abnormalities is to blame.

Absent Heat

An absent heat occurs when a bitch completely misses her cycle. Even in healthy bitches, the occasional absent cycle can crop up for seemingly inexplicable reasons. However, frequent absent heats often indicate an underlying problem with your bitch. Absent heat cycles may occur due to hypothyroidism or ovarian tumors. If you suspect that your bitch is undergoing absent heats, consider talking to your vet about your options. Your vet can take blood serum samples from your pet to test her progesterone levels. If her progesterone does not rise around the time her heat should start, it indicates that her heat cycle is not taking place.

Silent Heat

Silent heat, also called sub-estrus, occurs when your bitch ovulates but shows little or no signs of being in heat. Male dogs are still attracted to a bitch in a silent estrus. If you suspect that your bitch is having silent heat cycles, your vet might recommend progesterone testing to confirm the problem. Whilst in a silent heat, your bitch’s progesterone and luteinizing hormone levels should rise over the course of her cycle.

Split Heat

A split heat occurs when your bitch’s heat cycle begins but stops abruptly before ovulation. During proestrus, your bitch produces blood-tinged discharge, her vulva swells, and her behavior might change. While males are attracted to her, she won’t accept them yet. Her estrogen levels rise significantly as she prepares for ovulation. By the time estrus should begin, your bitch’s cycle comes to a halt. This is because your bitch is unable to produce enough luteinizing hormone to trigger ovulation. Luckily, a split heat often resumes after two to three weeks in younger dogs.

Prolonged Heat

Prolonged heat occurs when your bitch’s heat cycle lasts for longer than 21 days. In young dogs, prolonged heats are fairly common and are not a reason for concern. However, in older dogs of two to three years, prolonged heat may signal an underlying problem. The main causes of prolonged heat cycles are estrogen-producing ovarian cysts and granulosa cell tumors of the ovaries. While ovarian cysts may regress on their own, ovarian tumors require surgical intervention. Your vet will use ultrasonography to diagnose your pet’s problem.

Аn ovarian cyst can potentially cause a dog to not come into season (estrus). Ovarian cysts are fluid-filled sacs that develop on or within the ovaries. They can disrupt the normal hormonal balance and functioning of the reproductive system, leading to irregular or absent heat cycles.

Ovarian cysts can affect the production and release of hormones necessary for the initiation of estrus. Depending on the size and type of cyst, it may interfere with the maturation and release of eggs or cause hormonal imbalances that disrupt the normal reproductive cycle.

If a dog has an ovarian cyst, it may exhibit signs such as extended periods between heat cycles, prolonged or irregular cycles, or a complete absence of heat cycles. Other symptoms that may be present include behavioral changes, abnormal vaginal discharge, or swelling in the abdominal area.

If you suspect that your dog has an ovarian cyst or if she is experiencing abnormal reproductive symptoms, it’s important to consult with a veterinarian. They can perform a thorough examination, conduct diagnostic tests, such as ultrasound or hormone level analysis, and recommend appropriate treatment options. Treatment may involve hormonal therapy or, in some cases, surgical removal of the cyst or ovaries.

Common Questions

Need to know more about why your dog has not come into season yet? Feel free to browse through our FAQ section for even more questions. If in doubt about your pet’s health, always ask your vet for advice.

Why is my dog not coming into heat?

If your vet confirms that your dog is skipping heat cycles, there are several potential causes for it. While ovarian tumors are rare in dogs, they are still a possible explanation and your vet will need to carry out ultrasonography to diagnose them. Ovarian tumors cause irregular cycles in female dogs, varying from prolonged heats to skipped heats.

Similarly, ovarian cysts cause irregular cycles by influencing hormone production. Another medical cause is hypothyroidism. Hypothyroidism is characterized by a lack of thyroid hormone production, leading to a slower metabolism. This affects every system in your dog’s body, including their reproductive system. This might manifest as skipped heats, miscarriages, and puppy absorption.

What is a silent season in dogs?

Silent heat occurs when your bitch ovulates but shows no outward signs of being in heat. This means that her vulva won’t swell, she produces little to no discharge, and she shows little to no interest in male dogs. Because there are no obvious signs of estrus, many newer owners assume that their bitch has not undergone her first heat cycle yet.

To confirm that your bitch is experiencing silent heats, your vet will take blood serum samples for testing. They will test for progesterone and luteinizing hormone (LH) levels. If your bitch’s heat is silent, her progesterone and LH will rise as normal to prepare for ovulation. The cause of silent heat cycles in bitches is not clear.

Can a dog be on heat and not bleed?

Some bitches will come into heat but not bleed, or only bleed a small amount. This is not abnormal. Depending on the dog, the amount and color of discharge differ. In individuals who do produce discharge, vaginal discharge may be very bloody, blood-tinged, or even pink. Towards the end of estrus, her discharge becomes watery and often comes with more mucous. By the time diestrus comes around, your bitch’s discharge becomes more watery until it subsides completely.

If your bitch undergoes a silent heat, she may not bleed alongside not showing other signs of estrus. During a silent heat, your bitch’s vulva won’t swell and she might not show interest in male dogs. Despite these unusual occurrences, a bitch in a silent heat can still get pregnant.

When do dogs stop coming into season?

Unlike humans, female dogs don’t stop having cycles when they get older. Your unspayed dog will continue to come into heat once or twice a year for the rest of their lives unless they are pregnant or spayed. Older dogs tend to undergo their estrus cycle less often, and the time gaps between the cycles often increase.

If your elderly bitch is not spayed, there are some risks to consider. Mammary cancer, uterine cancer, ovarian cancer, and pyometra are possible complications of leaving your bitch intact. With every estrus cycle, your older bitch’s risk of pyometra increases. For this reason, many owners choose to spay their bitch once she is no longer able to safely have puppies.

silent season in dogs
Silent heat is when there are no obvious signs of the dog being in heat.

Reasons why your dog has not come into season yet include her age, breed, diet and a range of underlying health conditions. If you are concerned about your bitch’s irregular estrus cycles, be sure to contact your vet for advice.

One comment on “Why Has My Dog Not Come Into Season Yet?”

  1. Elizabeth Devery

    My 2.5 Yr old bitch has an underlying problem with food, therefore is underweight. Her last season was 3 months late and then it only lasted 9 days. She is due in season 8th August but again no sign. She is a Crossbreed and I want her spayed this year if possible.

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