What is a normal menstrual cycle?

Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
A menstrual cycle normally lasts from 21 to 35 days, although teens and women in their forties may have longer, irregular cycles up to 45 days. If you are nearing menopause, you can expect that the time between your periods will probably get longer and eventually stop. Other signs of approaching menopause are hot flashes and mood changes.

A normal period usually lasts about three to five days; anything longer than seven days is considered prolonged bleeding.

If you are you are not approaching menopause and your period becomes irregular, it could be a sign of stress, dramatic weight loss, or conversely, sudden weight gain. All these conditions can affect your body's hormone levels and may cause changes in the length of your cycle. Medications such as antidepressants also can be a common, harmless cause of cycle changes. Certain endocrine conditions such as polycystic ovaries and thyroid disorders also can cause irregular cycles; visit a specialist regarding these disorders.
Jill A. Grimes, MD
Family Medicine
Menstrual periods, like bowel movement patterns, are unique to each individual. In the textbooks, periods occur every 28 days and last for a week. In reality, there is more variation.

When an adolescent starts having periods, her periods are often very unpredictable for the first six months to a year. At that point, most young women establish a pattern that they can recognize and therefore predict when their next period should arrive. Some may be as short as 21 days, others beyond 30, but what is important is recognizing what your pattern is. Consider the modern calendar -- a period tracker app -- for your phone to figure out your cycle.
Are terrible cramps okay? Well, no -- absolutely not! First of all, we have several medicines that might help, from ibuprofen and its cousins to using the contraceptive pill to help decrease the amount of cramping and blood loss.
Additionally, for women who have pain outside the range of normal, doctors begin to be concerned about endometriosis, a condition where extra tissue that belongs inside the uterus may have migrated outside of the uterus into the pelvis and be stuck on the intestines or fallopian tubes, causing pain especially at ovulation (mid-cycle).

Additionally, if it's PMS symptoms that drive you nuts (bloating, headaches, mood swings, and breast tenderness), there are simple behavioral modifications like quitting caffeine, increasing your calcium intake, and increasing aerobic exercise that will help.

Please do not suffer in silence! If you have terrible periods that make you miss school, work, or fun stuff. Make an appointment with your doctor.
Patricia Geraghty, NP
Women's Health
Remember sex education in primary school? For me, this occurred in the fifth grade, with all the boys in one room and all the girls in another, but both groups hearing about "Your Wonderful Body." We learned that women have vaginal bleeding, called a menses, and this cycle of bleeding starts every 28 days. Well, bless those fifth grade teachers, they did the best job they could. How many women actually bleed every 28 days every month? The answer is one in eight women, and evidently they all grow up to be fifth grade teachers!

In reality, the cyclical bleeding is a result of complicated communication, with hormones as the messengers, between the brain and the ovaries. This results in the maturation and ovulation of an egg, the development of the lining of the uterus, and sloughing of this lining if a pregnancy does not occur. 95% of women will start bleeding between 24 to 38 days. Irregularity is more common than we thought with the time between bleeding varying by up to 20 days in 95% of women. The bleeding itself may last between 4 and 6 days (Frazer I, et al. Steril Fertil 2007).

In young teens, the brain part of the communication is immature and this causes cycles to be very irregular. In later years, the ovary part of the communication has aged, and again cycles are irregular. Women in their early forties typically experience shorter cycles and heavier bleeding. When closer to menopause, women begin to skip cycles or have more days between bleeding.

If your pattern changes suddenly or if you experience problems with your cycles that distress you, you should see your health care provider.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.