Besides pregnancy, there are a number of possible reasons for a missed period. Pregnancy is by far the most common cause of a missed period, but there are some other medical reasons and lifestyle factors that impact your menstrual cycle. Extreme weight loss, hormonal irregularities, and menopause are among the most common causes if you're not pregnant.

You may miss a period for one or two months, or you may experience complete amenorrhea, which is a lack of menstruation for three or more months in a row. Here are 10 common reasons your period may be delayed:

​Illustration by Cindy Chung, Verywell

Stress

Profound stress alters the production of a gonadotrophin-releasing hormone (GnRH), interfering with ovulation and regular menstruation.﻿﻿

The type of stress that's severe enough to affect your menstrual period usually isn't just a matter of having a lot going on at work or school.

If you're coping with an overwhelming situation or experiencing prolonged anxiety, with more than one missed period, talk to your doctor and get a referral for counseling to help you decide what to do about the issues that are causing you stress. Once your stress is back to a manageable level, it can sometimes take a few months or more for your cycles to become regular again.

Extreme Exercise

Extreme exercise can cause alterations in pituitary hormones and thyroid hormones, resulting in changes in ovulation and menstruation.﻿﻿ Don't worry about exercise causing you to miss your cycle if you work out for one or two hours per day. It takes strenuous exercise for hours and hours every day to produces these hormonal changes.

If you are planning on exercising for hours every day, be sure to see a sports medicine doctor who can work with you on maintaining optimal nutrition, recommended stretching, and blood testing as needed, so that your body can support all of the physical demands that you are putting on it.

Illness

Chronic conditions that can affect your menstrual cycles include thyroid disease, polycystic ovarian syndrome (PCOS), pituitary tumors (which may or may not be cancer), diseases of the adrenal gland, ovarian cysts, liver dysfunction, and diabetes.﻿﻿

When any of these illnesses interfere with your cycle, it may not return to normal until the condition is treated. Congenital chromosomal conditions such as Turner syndrome and androgen insensitivity syndrome typically cause menstrual and fertility problems and are often associated with amenorrhea.

Acute illness, such as pneumonia, a heart attack, kidney failure, or meningitis, can result in rapid weight loss and nutritional deficiency or hormone dysfunction, which can cause you to miss your period during the illness. After the illness is resolved, it might take a few months before your period returns again.

A Change in Your Schedule

Changing schedules can throw off your body clock.﻿﻿ If you frequently change work shifts, going from days to nights, and particularly if your schedule is erratic, your period can be fairly unpredictable.

Generally, changes in schedule shouldn't cause you to completely miss your period but can cause it to start earlier or later than expected. Your cycle can also change by a few days if you experience jet lag.

Medications

Some medications, such as antidepressants, antipsychotics, thyroid medications, anticonvulsants, and some chemotherapy medications, may cause your period to be absent or delayed.﻿﻿

Hormonal contraceptives like Depo-Provera, progesterone-only MiniPill, Mirena IUD, and Nexplanon can also influence your cycle.

Each type of contraceptive has its own list of anticipated effects on your menstrual cycle, and some are associated with heavy periods, some with light periods, and some with amenorrhea.

Weight Changes

Being overweight, underweight, or experiencing drastic changes in weight all impact your cycle.﻿﻿ Obesity influences estrogen and progesterone and may even result in decreased fertility. Very high body mass index (BMI) is associated with missed periods, and weight loss can help regulate the menstrual cycle for women who are obese.

Being severely underweight interferes with regular menstrual cycles as well. When the body lacks fat and other nutrients, it cannot produce hormones the way it should.

Women with anorexia (very low food intake) or who burn far more calories with exercise than what they consume by eating may experience amenorrhea. Typically, weight gain will help your periods to return.

Rapid weight changes, which can include weight gain or weight loss due to illness, medication, or dietary changes, may interfere with hormone production or release, causing you to miss one period or more.

Recently Started Periods

A normal menstrual cycle lasts from 21 to 35 days in healthy women, but it can vary. This is especially true for young women who are just starting to get their periods or for women who have not had periods for several years and are starting again.

A young woman who has had just a few cycles may go months without another one until a regular pattern begins.﻿﻿ And women who have not had a period due to contraceptive use, hormonal therapy, or illness may not resume having a regular period every month right away.

Perimenopause and Menopause

Perimenopause is the period of time of transition from reproductive age to a non-reproductive age. Your periods may be lighter, heavier, more frequent, or less frequent.﻿﻿ In most cases, they'll just be something different than what you're used to.

Menopause is when you have reached the point in your life where you will no longer ovulate or menstruate. The average age of menopause is 51 years old.

Breastfeeding

You may not have periods at all or you may have infrequent or very light periods when breastfeeding,﻿﻿ particularly if breastfeeding provides your baby with all or almost all of his or her caloric intake.

Many women believe that breastfeeding is a form of birth control, but it's is not. Even if you don't have periods when you are breastfeeding, you can get pregnant, so use another form of birth control if you are not ready for another little one.

Ectopic Pregnancy

If you think that you can't be pregnant because you have an IUD, there is a small chance that your missed period could be a sign of an ectopic pregnancy.﻿﻿ Ectopic pregnancy can happen sometimes due to the shape of the device and may not cause you to test positive on a pregnancy test. Your doctor can confirm or exclude this possibility with a pelvic examination or an ultrasound.

When to Call Your Doctor

Missing a period or two, even when you suspect that you know the reason, is something that needs to be investigated by your doctor.﻿﻿

You should see your doctor urgently if you experience any of the following:

New or worsening headaches

Vision changes

Nausea or vomiting

Fevers

Hair loss

Breast secretions or milk production

Excess hair growth

A Word From Verywell

There are many reasons for late periods, and while most are not cause for alarm, you do need an evaluation and treatment if you have completely missed more than one period.

How your missed periods are treated depends on why you aren't having your period. The treatment can include lifestyle changes, such as diet or stress reduction, or may involve hormone replacement therapy.