Why is My Period Late?

The regular menstrual cycle lasts 28 days on average. That being said, anything from 21 to 35 days is considered normal for women who have yet to reach menopause.

If your last period was more than 35 days ago, it can be due to a wide range of reasons, one of which, as sometimes movies and TV shows like to bring to our attention, is pregnancy. It can also be due to stress, hormonal imbalances, or birth control pills, among many other reasons.

Chronic and/or serious health issues might play a role in late and missed periods. Also, obesity and extreme weight loss can cause somebody’s period to be late or missed, as well. If you’re wondering “why is my period late,” read on for a more detailed explanation of the major causes.


Many people often ascribe missing period to pregnancy. Future moms do not menstruate for the duration of their pregnancy. However, some women do experience some spotting in the initial weeks.

When an egg gets fertilized, the period stops and doesn’t resume until after the child is born. Commonly, one can expect the period to return six to eight weeks after childbirth if not breastfeeding. Otherwise, the waiting period can vary from a couple of months to the end of the breastfeeding period. However, this is only one of many other potential causes.


Stress is known to cause many health conditions and issues, including irregular menstruation by affecting the hypothalamus (part of the brain that regulates the cycle). Apart from the direct impact on the hypothalamus, stress can also cause sudden weight gain or loss, which on its own can disrupt the menstrual cycle.

If you suspect that stress is causing a late or missed period, you can try a number of relaxation techniques. For example, you could start exercising, meditation, or yoga. Also, you could change your lifestyle and introduce healthier habits, such as a healthier diet, going to bed earlier, spending more time outdoors, etc.


On average, menopause starts around the age of 52. Some women might experience its onset earlier or later. After going through 12 months without a period, a woman is considered to have gone through menopause.

That being said, the first symptoms usually start some 10 to 15 years earlier, which means that some women might start missing or experiencing irregular periods in their mid to late 30s. These symptoms are known as perimenopausal and are a signal that the estrogen levels are beginning to fluctuate.


Being overweight can affect the regularity of the menstrual cycle as well, which has been known to occur in obese persons.

However, the combination of obesity and missing/irregular periods might also be the sign of a deeper, more serious problem, such as PCOS (more about it later in the article).

In the case of obesity and menstrual problems, the doctor might order blood tests and ultrasound for the patient. The blood tests will show if there are any hormonal imbalances, while the ultrasound is for checking the ovaries for PCOS.

Low Weight/Weight Loss

Similar to obesity, being underweight might cause problems with menstruation. Low body fat can potentially throw off your menstrual cycle, as it can lower the hormone levels below the menstruation and ovulation threshold.

Aside from being underweight, a rapid weight loss can also throw your hormones off balance, consequently causing irregular or missing periods. Women suffering from eating disorders, such as bulimia or anorexia nervosa, may miss periods.

Women who participate in extremely hard and taxing sports, such as marathon running, might also experience missed periods.

The Pill

The birth control pill is one of the leading causes of changes in the duration and regularity of periods. You can expect the changes to happen both when you start using it, as well as when you stop. Due to the inclusion of progestin and estrogen hormones, birth control pills prevent your body from releasing unfertilized eggs.

Once you stop taking the pill, regular periods might not return for up to three months. Also, keep in mind that injected and implanted contraceptives can also affect your period.

Thyroid Gland Problems

Problems with the thyroid glands can lead to irregular or missing periods. Both the lowered and heightened activity of the thyroid can cause period problems. However, after taking medication and bringing the activity of the thyroid gland back to normal, your period should also stabilize.

Chronic Disease

It is not uncommon for chronic diseases to cause missing or late periods. Some of the most prominent examples include diabetes and celiac disease. Diabetic women, especially if poorly controlled, might experience problems with the menstrual cycle due to fluctuations in sugar levels.

On the other hand, celiac disease causes inflamed small intestine which might become damaged and make it difficult for your body to acquire important nutrients. The resultant deficiencies can cause changes in period regularity.

Hormonal Problems

Hormonal problems can be caused by a host of health issues and conditions. Some of them might even be inherited. Whatever the cause, unbalanced hormones can affect a woman’s menstrual cycle.

Hormonal imbalances can easily be discovered through a blood test. After the discovery, the root cause must be found and treated. Only after the hormonal balance has been restored will your period return to normal.

Insulin resistance is another issue that can cause period problems. This is closely related to PCOS.


PCOS (polycystic ovary syndrome) is a hormonal disorder most commonly tied to irregular and missed periods. In some cases, the syndrome might cause them to stop completely. PCOS causes a woman’s body to produce excessive amounts of androgen (a male hormone). The common result of which is the formation of cysts on one or both ovaries.

Women with PCOS might also experience excess body and facial hair, obesity, acne, and baldness (male pattern). Sometimes, the syndrome is treated with birth control pills to stimulate the production of estrogen. Untreated PCOS might cause endometrial cancer in newborn babies.


If you find yourself asking “why is my period late,” you should start keeping journal records of the start and end dates, as well as all symptoms and observances. This record can greatly help your doctor diagnose the problem.

If you haven’t been seeing your gynecologist regularly, now is a good time to start. However, if you have missed consecutive periods, lost or gained a lot of weight, been exposed to a lot of stress, had a positive pregnancy test, or noticed symptoms of PCOS, you should see your doctor as soon as possible.