Polymenorrhea and Other Period Problems

Frequent Menstrual Periods and Abnormal Uterine Bleeding Explained

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Polymenorrhea is the term for a menstrual cycle abnormality in which a woman gets her period very frequently—every 20 days or even less often—meaning her menstrual cycle is shorter than 21 days long. So instead of having an average of 12 periods each year, she could have as many as 17 or more. 

"Normal" Menstrual Cycles vs. Polymenorrhea

To put this in perspective, a normal menstrual cycle for an adult woman is 21 days to 35 days long.

For an adolescent, the normal cycle is from 21 days to 45 days. The first day there's any amount of bleeding is considered day one of a new cycle. The last day is the one before the next period begins. 

The term polymenorrhea is somewhat outdated, as are terms for other period abnormalities, such as menorrhagia (heavier than normal menstrual flow) and metrorrhagia (irregular bleeding between periods). These descriptive terms are now being replaced with the single term abnormal uterine bleeding.

For some women, a shorter-than-average menstrual cycle is normal. As long as bleeding occurs at regular intervals and the flow isn't too heavy, there's usually no reason to worry about a shorter cycle or to treat it in any way.

When Short Cycles Require Treatment

Having a period so frequently can be inconvenient and bothersome and may be a sign of a shorter than normal luteal phase (the phase between ovulation and menses) or anovulatory cycles.

If you are wondering about your short cycles and frequent periods, you may want to discuss your cycle with your gynecologist. Your doctor may recommend a combined hormonal contraceptive to lengthen the intervals between your periods (or rather, withdrawal bleeds, as is the case when using hormonal birth control).

Another option is to use a contraceptive method that temporarily stops the menstrual flow or makes bleeding very light, such as MirenaDepo-Provera, or Nexplanon. Controlling the length between your withdrawal bleeds or reducing the amount of bleeding you have to deal with during each period can be a big improvement over having a period every three weeks. However, it is important to remember that treatment may not be necessary for more frequent periods with a normal amount of menstrual flow.

Causes of Problem Periods

Abnormal uterine bleeding can be used to describe heavy menstrual bleeding or intermenstrual bleeding (bleeding between periods). Any of these could be caused by a structural problem in the uterus, such as overgrowths of cells in the lining of the uterus called polyps or tumors that are known as fibroids. (Don't be alarmed by the word tumor if your doctor discovers you have fibroids; they're benign 99 percent of the time). Abnormal bleeding also can be caused by nonstructural issues such as ovulation problems or blood clotting disorders.

That's one reason you should see your gynecologist if your period changes in any significant way. Another reason is if you have a heavy flow or your periods are very long.

(The average period lasts about five days.) It could cause you to become anemic, meaning your body can't produce enough hemoglobin to restock your blood cells after losing menstrual blood.

Symptoms of anemia include pale skin, weakness, fatigue, and lightheadedness. If you have long, heavy periods and any of these symptoms, see your gynecologist. He or she may recommend a change of diet or iron supplements if you are anemic due to menstrual blood loss.


Abnormal Uterine Bleeding. MedlinePlus. U.S. National Library of Medicine. 

Abnormal Vaginal Bleeding (Irregular Periods) in Adults. The Permanente Medical Group. 

Bradley L. Menstrual Dysfunction. Cleveland Clinic.

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