Worried about a late period, but know you’re not pregnant? Missed or late periods happen for many reasons other than pregnancy. Common causes can range from hormonal imbalances to serious medical conditions.

There are also two times when it’s typical for your period to be irregular: when it first begins, and when the menopause transition starts. As your body goes through the transition, your cycle can become irregular.

Most people who haven’t reached menopause usually have a period approximately every 28 days. However, a healthy menstrual cycle can range from every 21 to 40 days. If your period doesn’t fall within these ranges, it could be because of one of the following reasons.

Chronic stress can throw off your hormones, change your daily routine, and even affect the part of your brain responsible for regulating your period: your hypothalamus. Over time, stress can lead to illness or sudden weight gain or loss, all of which can impact your cycle.

If you think stress might be throwing off your period, try practicing relaxation techniques and making lifestyle changes.

Chronic stress can also affect other health conditions you’re living with, so addressing it yourself, or with the help of a medical professional, is an important part of taking care of your overall well-being.

People who have eating disorders, such as anorexia nervosa or bulimia, may experience irregularities in their cycle. Losing too much weight can cause irregular periods, and may even stop your cycle altogether. This is because not having enough body fat can pause ovulation.

Getting treatment for your eating disorder and getting to the point where your body fat is optimal again can return your cycle back to its original length.

People who participate in extreme exercise, such as marathons, may also experience cycle irregularities as well.

In the same way that living with low body weight can cause hormonal changes, living with high body weight can also cause irregularities.

Obesity can cause the body to produce an overabundance of estrogen, which is a key reproductive hormone. Too much estrogen can cause irregularities in your cycle, and may even stop your periods altogether.

If your doctor has determined that obesity is a factor in your late or missed periods, they may advise you to lose weight through lifestyle changes, such as a focusing on nutrient-dense foods and exercising.

Polycystic ovary syndrome (PCOS) is a condition that causes your body to produce more of the male hormone androgen. Cysts form on the ovaries as a result of this hormone imbalance. This can make ovulation irregular or stop it altogether.

Other hormones, such as insulin, may also become unbalanced. This is due to insulin resistance, which is often associated with PCOS.

Treatment for PCOS focuses on relieving symptoms. Your doctor may prescribe birth control or another medication to help regulate your cycle.

You may experience a change in your cycle when you go on or off birth control. Birth control pills contain the hormones estrogen and progestin, which prevent your ovaries from releasing eggs. It can take up to 3 months for your cycle to become consistent again after you stop taking the pill.

Other types of contraceptives that are implanted or injected can cause missed periods as well.

Chronic diseases, such as diabetes and celiac disease, can also affect your menstrual cycle. Changes in blood sugar are linked to hormonal changes, so even though it’s rare, unmanaged diabetes could cause your period to be irregular.

Celiac disease causes inflammation that can lead to damage in your small intestine, which may prevent your body from absorbing key nutrients. This can cause irregular or missed periods.

Other chronic conditions that may lead to cycle irregularities include:

Most vagina owners begin menopause between the ages of 45 to 55. Those who develop symptoms around age 40 or earlier may be experiencing premature ovarian insufficiency (POI), or early natural menopause.

About 1 percent of women in the United States experience POI. While this condition can arise from the surgical removal of the ovaries, other causes include genetic disorders and autoimmune conditions.

If you’re experiencing missed periods and you’re 40 years old or younger, contact your doctor to talk about POI testing and treatment.

An overactive or underactive thyroid gland could also be the cause of late or missed periods.

The thyroid regulates your body’s metabolism, so hormone levels can be affected as well. Thyroid issues can usually be treated with medication. After treatment, your period will likely return to your normal cycle.

If your periods seem irregular, or you’ve missed a period but know you’re not pregnant, it’s a good idea to talk with your doctor ASAP, as there are many reasons and conditions that could be causing the issue.

Your doctor can properly diagnose the reason for your late or missed period and discuss your treatment options. If you can, keep a record of changes in your cycle as well as other health changes. This will help them make a diagnosis.

If you have the following symptoms, contact a doctor immediately, or call 911:

Just as every person is different, every menstrual cycle is different. While 28 days is the generalized cycle length, cycles can range from 28 to 40 days.

Occasional cycle irregularities can happen for a variety of reasons, from chronic stress, to weight loss or weight gain, to stopping or starting birth control.

If you’ve noticed that your cycle has been irregular lately, or you’ve missed a period and know for a fact you’re not pregnant, it’s a good idea to talk with your doctor right away. The quicker they can make a diagnosis, the quicker you can work on regulating your cycle again.

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