Prolonged Periods in Teenagers

Teens' periods are often erratic, irregular and unpredictable during the first few years of menstruation. It takes time for hormones to settle down into a regular menstrual pattern. The first few menstrual cycles are especially likely to follow an erratic pattern, according to the American Academy of Pediatrics. Prolonged periods can indicate an undiagnosed health issue or lead to other health problems.

Menstrual Norms

The average time between periods is 28 days, but for teens, anything from 21 to 45 days is normal. By age 19 or 20, a teen's normal menstrual cycle will be established, usually lasting between 21 and 34 days. Bleeding usually last three to five days, but can be as short as two days or as long as seven. The average blood loss during a menstrual period is around 30 milliliters, or 1 ounce.

Clotting Problems

The most common cause of heavy periods in teens can also cause prolonged menstrual bleeding 2. A hereditary clotting disorder called von Willibrand disease affects around 1 percent of Americans; around one in six teens who seek emergency room treatment for very heavy periods have this disorder, according to the American Academy of Pediatrics. Menstrual bleeding that lasts longer than one week might indicate that a teen has this disorder, states. Blood tests help diagnose Von Willibrand disease. If you have any questions about your teen daughter and her periods, consult with her pediatrician for follow-up.

Hormonal Imbalances

An imbalance between sex hormones such as estrogen, progesterone and male androgens such as testosterone -- yes, girls produce this dominant male hormone, just as men produce small amounts of estrogen -- can cause heavy or prolonged menstrual cycles. High androgen levels can cause polycystic ovary syndrome, more commonly called PCOS. Teens with PCOS often don't ovulate; the uterine lining becomes overly thick and then breaks down, often resulting in irregular or continuous bleeding. Teens with PCOS may also suffer from acne, and excess facial and body hair. Blood tests and a gynecological exam from her pediatrician can diagnose PCOS.

Uterine Issues

Problems within the uterus itself can also cause prolonged bleeding in teens as well as adults. Abnormal but benign uterine growths such as polyps or fibroids or cancerous growths can cause bleeding beyond the normal seven-day limit for menstrual bleeding. Teens with irregular but prolonged or erratic vaginal bleeding should undergo a gynecological exam from her pediatrician.


Teens who lose 80 ml, or just under 3 ounces, of blood in the menstrual flow each month have a high risk of becoming anemic. Being anemic, ironically, also increase the risk of prolonged or heavy menstrual bleeding. Teen girls often follow low-protein diets that can worsen anemia. Symptoms of anemia include pallor, fatigue, shortness of breath with exertion, irritability and increased bleeding tendencies and bruising. A simple blood test can determine whether a teen is anemic. Iron supplements and treatment to decrease abnormal bleeding help treat anemia. If either you or your teen has any concerns, follow up with her pediatrician.