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Women's Health

Abnormal Period Cycle



I am almost 21yrs old, I have been getting my period since I was 14 and have always regularly had it at 28 day intervals. However,for the last three months my cycle has changed, instead of 28 days it became 25, then 21 and now it`s 18 days. I am not under any stress and have a pretty relaxed life style. What could be causing this irregularity?


Many women do not have clock-work-like menstrual periods. This can be due to a variety of reasons, including weight gain or loss, use or change in hormonal contraceptives, miscarriage, thyroid problems, excessive weight gain or weight loss. Additionally, the menstrual cycle can change with stress (either positive or negative), and if you are consistently around other females (eg. dorm or athletic team).

Talk with your health care provider if you continue to be concerned. 

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Response by:

Linda A Bernhard, PhD, RN Linda A Bernhard, PhD, RN
Professor Emeritus
College of Nursing
The Ohio State University