Menstrual cycle: What's normal, what's not
Medically reviewed by Drugs.com. Last updated on Dec 6, 2022.
Do you know when your last menstrual period began or how long it lasted? If not, it might be time to start paying attention.
Tracking your menstrual cycles can help you understand what's normal for you, time ovulation and identify important changes — such as a missed period or unpredictable menstrual bleeding. While menstrual cycle irregularities usually aren't serious, sometimes they can signal health problems.
What's the menstrual cycle?
The menstrual cycle is the monthly series of changes a woman's body goes through in preparation for the possibility of pregnancy. Each month, one of the ovaries releases an egg — a process called ovulation. At the same time, hormonal changes prepare the uterus for pregnancy. If ovulation takes place and the egg isn't fertilized, the lining of the uterus sheds through the vagina. This is a menstrual period.
The menstrual cycle, which is counted from the first day of one period to the first day of the next, isn't the same for every woman. Menstrual flow might occur every 21 to 35 days and last two to seven days. For the first few years after menstruation begins, long cycles are common. However, menstrual cycles tend to shorten and become more regular as you age.
Your menstrual cycle might be regular — about the same length every month — or somewhat irregular, and your period might be light or heavy, painful or pain-free, long or short, and still be considered normal. Within a broad range, "normal" is what's normal for you.
Keep in mind that use of certain types of contraception, such as extended-cycle birth control pills and intrauterine devices (IUDs), will alter your menstrual cycle. Talk to your health care provider about what to expect.
When you get close to menopause, your cycle might become irregular again. However, because the risk of uterine cancer increases as you age, discuss any irregular bleeding around menopause with your health care provider.
How can I track my menstrual cycle?
To find out what's normal for you, start keeping a record of your menstrual cycle on a calendar. Begin by tracking your start date every month for several months in a row to identify the regularity of your periods.
If you're concerned about your periods, then also make note of the following every month:
- End date. How long does your period typically last? Is it longer or shorter than usual?
- Flow. Record the heaviness of your flow. Does it seem lighter or heavier than usual? How often do you need to change your sanitary protection? Have you passed any blood clots?
- Abnormal bleeding. Are you bleeding in between periods?
- Pain. Describe any pain associated with your period. Does the pain feel worse than usual?
- Other changes. Have you experienced any changes in mood or behavior? Did anything new happen around the time of change in your periods?
What causes menstrual cycle irregularities?
Menstrual cycle irregularities can have many different causes, including:
- Pregnancy or breast-feeding. A missed period can be an early sign of pregnancy. Breast-feeding typically delays the return of menstruation after pregnancy.
- Eating disorders, extreme weight loss or excessive exercising. Eating disorders — such as anorexia nervosa — extreme weight loss and increased physical activity can disrupt menstruation.
- Polycystic ovary syndrome (PCOS). Women with this common endocrine system disorder may have irregular periods as well as enlarged ovaries that contain small collections of fluid — called follicles — located in each ovary as seen during an ultrasound exam.
- Premature ovarian failure. Premature ovarian failure refers to the loss of normal ovarian function before age 40. Women who have premature ovarian failure — also known as primary ovarian insufficiency — might have irregular or occasional periods for years.
- Pelvic inflammatory disease (PID). This infection of the reproductive organs can cause irregular menstrual bleeding.
- Uterine fibroids. Uterine fibroids are noncancerous growths of the uterus. They can cause heavy menstrual periods and prolonged menstrual periods.
What can I do to prevent menstrual irregularities?
For some women, use of birth control pills can help regulate menstrual cycles. Treatment for any underlying problems, such as an eating disorder, also might help. However, some menstrual irregularities can't be prevented.
In addition, consult your health care provider if:
- Your periods suddenly stop for more than 90 days — and you're not pregnant
- Your periods become erratic after having been regular
- You bleed for more than seven days
- You bleed more heavily than usual or soak through more than one pad or tampon every hour or two
- Your periods are less than 21 days or more than 35 days apart
- You bleed between periods
- You develop severe pain during your period
- You suddenly get a fever and feel sick after using tampons
If you have questions or concerns about your menstrual cycle, talk to your health care provider.