Sad woman with negative pregnancy test and calendarMissed 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 in a woman’s life when it’s totally normal for her period to be irregular: when it first begins, and when menopause starts.

Women typically begin getting their periods anywhere from age 10 to 15. During the first two years after starting your period, your hormones may still be adjusting. This can cause late or missed periods. Menopause generally begins between ages 45 to 55. As your body goes through the transition, your normal cycle can become irregular.

Most women usually have a period every 28 days between starting their period and menopause. However, a healthy menstrual cycle can range from every 21 to 35 days. If your period doesn’t fall within these ranges, it could be because of one of these reasons.

1. Stress
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.

2. Low Body Weight
Women with eating disorders, such as anorexia or bulimia, may experience missed periods. Weighing 10 percent below what’s considered a normal range for your height can change the way your body functions and stop ovulation. Getting treatment for your eating disorder and putting on weight in a healthy way can return your cycle to normal.

3. Obesity
Just as low body weight can cause hormonal changes, so can being overweight. Your doctor will recommend a diet and exercise plan if they determine that obesity is a factor in your late or missed periods.

4. Polycystic Ovary Symptom (PCOS)
PCOS is a condition that causes the 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.

5. Birth Control
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 the ovaries from releasing eggs. It can take up to six months for your cycle to become consistent again after stopping the pill. Other types of contraceptives that are implanted or injected can cause missed periods as well.

6. Chronic Diseases
Chronic diseases such as diabetes and celiac disease also can affect your menstrual cycle. Changes in blood sugar are linked to hormonal changes, so while rare, poorly controlled diabetes could cause your period to be irregular.

7. Early Menopause
Most women begin menopause between ages 45 to 55. Women who develop symptoms around age 40 or earlier are considered to have early menopause. This means your egg supply is winding down, and the result will be missed periods and eventually the end of menstruation.

8. Thyroid Issues
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 normal.

When to See a Doctor
Your doctor can properly diagnose the reason for your late or missed period and discuss your treatment options. Keep a record of changes in your cycle as well as other health changes to show your doctor. This will help them make a diagnosis.

Contact a doctor right away if you have unusually heavy bleeding, a fever, severe pain, nausea and vomiting, or bleeding that lasts longer than seven days.