The possible reasons for why your period's late will always include pregnancy if you're sexually active, but it's not the only cause. A missed period can be related to your age and stage of life cycle. Medical factors and lifestyle choices, including stress, smoking, weight changes, and exercise, can also affect your menstrual cycle.
If you're not pregnant, then hormonal changes are common causes of a missed period. These can include menopause as well as health conditions like polycystic ovary syndrome (PCOS). Depending on the cause, you may miss a period once or twice, or experience complete amenorrhea—meaning no period for three or more months in a row.
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Illustration by Cindy Chung for Verywell Health
1. Recently Started Periods
Not all age-related changes to your period will occur in older people. It's common for younger people, especially teens who have just started menstruating, to have irregular or missed periods.
It may take a little while for your period to happen every month. People who have not had a period due to contraceptive use, hormonal therapy, or illness also may not resume regular, monthly periods right away.
The average menstrual cycle (the day your period starts to the first day of your next period) is between 25 and 30 days, but it can range from 21 to 35 days or more and still be considered normal. If your cycle is longer than this, or longer than is usual for you, it's considered late.
2. Perimenopause
Perimenopause is the period of transition between reproductive age and a non-reproductive age. Your periods may be lighter, heavier, more frequent, or less frequent during this time. In most cases, they'll just be different than what you're used to.
3. Menopause
Menopause occurs as you reach an age when you will no longer ovulate or menstruate. The average age of menopause is 51 years old.
Premature menopause occurs in people younger than 40 and early menopause occurs in people between the ages of 40 and 45 years. Early menopause can occur naturally, or as a result of surgery (like having the uterus removed), cancer treatment with chemotherapy, or other issues.
4. Primary Ovarian Insufficiency
Primary ovarian insufficiency (POI) happens when the ovaries stop functioning normally before a person reaches the age of 40. It is sometimes called premature ovarian failure.
This can cause irregular periods and fertility problems to begin before the typical age of perimenopause. The cause of POI isn't well understood, but it is believed to be related to the function of the follicles. These are small sacs in the ovaries where eggs mature. In people with POI, there may not be enough working follicles.
5. Pelvic Inflammatory Disease (PID)
Pelvic inflammatory disease is a bacterial infection that occurs in females, typically following a sexually transmitted infection (STI) that has been left untreated. While an STI like chlamydia or gonorrhea doesn't always lead to missed periods as a symptom, it may occur with PID.
In addition to irregular periods, you may also experience abdominal pain, fever, and pain with sex.
6. Stress
Intense stress interrupts the production of gonadotrophin-releasing hormone (GnRH)—a hormone that regulates ovulation and the menstrual cycle.
Missing one period while going through a very stressful situation is not uncommon. People who have significant or prolonged levels of stress may experience an irregular menstrual cycle. A professional counselor or healthcare provider can offer strategies to handle high stress levels, so consider a consultation if you miss three or more periods.
Disruptive Changes in Your Schedule
Changing schedules can throw off your body clock. If you frequently change day-night work shifts, or if your schedule is unpredictable, your period can be, too. A scheduling change shouldn't cause a completely missed period, but it can cause it to be earlier or later than expected. Your cycle can also change if you experience jet lag.
7. Polycystic Ovary Syndrome (PCOS)
People with polycystic ovary syndrome (PCOS) have a hormonal imbalance that can cause delayed or irregular periods. If you have PCOS, you will likely have other symptoms besides just an irregular menstrual cycle. Some of these may include:
- Weight gain/trouble losing weight
- Infertility
- Acne
- Hair loss or thinning
- Hair growth on the face or body
8. Low Body Weight
Rapid weight changes due to illness, medication, or dietary changes can interfere with hormone production or release. In turn, this may cause you to miss periods. Chronic issues, like malnutrition and being underweight due to anorexia nervosa, can also lead to missed periods.
When the body lacks fat and other nutrients, it cannot produce hormones the way it should. Typically, weight gain will cause periods to return.
9. Obesity
Obesity influences estrogen and progesterone regulation and is associated with missed periods. It may even lead to issues with fertility. Weight loss can help regulate the menstrual cycle for people diagnosed with obesity.
10. Chronic Diseases
People with thyroid disease have too much or too little thyroid hormone, which plays a role in regulating the menstrual cycle. When you don't have the right amount of thyroid hormone, you might have periods that are irregular. Some people with thyroid disease may miss their periods altogether, often for a few months or more.
Other chronic conditions that can affect your menstrual cycle include:
- Pituitary tumors (which may or may not be cancer)
- Diseases of the adrenal gland
- Ovarian cysts
- Liver dysfunction
- Diabetes
- Celiac disease
Certain conditions that are present at birth, such as Turner syndrome and androgen insensitivity, typically cause menstrual and fertility problems. These congenital conditions are often associated with amenorrhea.
11. Acute Illness
Acute illness, such as pneumonia, kidney failure, or meningitis, can result in rapid weight loss, nutritional deficiency, or hormone dysfunction.
Sudden medical conditions such as a heart attack also can result in a missed period. Some studies suggest that people with a history of irregular periods may be more at risk of heart disease, but more research is needed to understand this relationship.
12. Extreme Exercise
Extreme exercise can cause changes in pituitary hormones and thyroid hormones, which can impact ovulation and menstruation. Working out for one or two hours per day shouldn't affect your menstrual cycle. It usually takes hours upon hours of demanding exercise every day for these hormonal changes to occur.
If you are planning on exercising that much, you may want to consult with a sports medicine healthcare provider. Their job is to help your body support all of the physical demands that you are putting on it. This may include:
- Optimizing your diet with nutritious foods that boost your energy
- Teaching you stretching techniques to reduce physical stress
- Performing blood tests to check for iron or vitamin deficiencies, hormonal imbalances, dehydration, and more
13. Medication
Some medications, such as antidepressants, antipsychotics, thyroid medications, seizure drugs, and some chemotherapy medications, may cause your period to be absent or delayed.
Birth Control
Contraceptives can help regulate your periods, but stress, diet, weight, and other factors can still affect your menstrual cycle. Different types of contraceptives can lead to heavy periods, light periods, or missed periods. Some birth control methods can lead to complications, such as the risk of ectopic pregnancy in people using the intrauterine device (IUD).
14. Breastfeeding
You may have light periods, infrequent periods, or amenorrhea when breastfeeding. Many people believe that breastfeeding is a form of birth control. While it can reduce your chances of getting pregnant, it is not 100% effective.
Even if you don't have periods when you are breastfeeding, you can get pregnant. If you are not ready for another child, you should use a backup contraceptive.
When to Call Your Healthcare Provider
Missing a period every once in a while is usually not cause for concern. How much of a delay is normal for your period? It depends. On average, a menstrual cycle lasts 28 days, but 38 days could also be within the range of normal. Your cycle will change throughout your life, so at some time, you're likely to experience a late period when you're not pregnant.
That said, you should contact your healthcare provider if you miss more than one period, or if your missed period is accompanied by new or unusual symptoms. It could be another condition, such as an infection, ectopic pregnancy, or PCOS, with symptoms that include:
- New or worsening headaches
- Abdominal pain
- Vision changes
- Nausea or vomiting
- Fevers
- Hair loss
- Breast discharge or milk production
- Excess hair growth
Summary
There are many reasons for late periods. These are often related to changes in the body that cause a hormonal imbalance, such as stress, certain illnesses, or medication. While most are not cause for alarm, you do need an evaluation and treatment if you have completely missed more than one period.