Why Is My Period Late?

If you know you aren't pregnant, one of these may be the cause

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One of the most frequent questions about menstruation is, "Why is my period late?" Pregnancy is the most common cause of the absence of menstruation (amenorrhea) in women of childbearing age who have been having regular periods. But you may know you are definitely not pregnant. What else can cause an absence of menstruation?

Causes of Late or Missing Periods—Other Than Pregnancy

  • Breastfeeding: Breastfeeding mothers will often experience amenorrhea. However, ovulation may still occur and pregnancy is possible even without menstruation.
  • Stress: Are you experiencing an unusual amount of stress in your life? Emotional stress is another possible cause of the absence of menstruation. Eliminating the stress usually will cause menstruation to resume.
  • Medications: What kind of medications are you currently taking? Certain medications such as contraceptives (oral, implanted, and injected), oral corticosteroids, antidepressants, antipsychotics, thyroid, and some chemotherapy drugs may cause amenorrhea for some women.
  • Eating Disorders and Malnourishment:  Women who are malnourished or extremely underweight with less than 15 to 17 percent body fat often experience amenorrhea. This occurs in women with eating disorders such as anorexia or bulimia.
  • Sudden Weight Loss from Dieting: If you've been on a strict diet and lost a lot of weight suddenly, you may stop having your period.
  • Obesity: Obese women are more likely to miss their periods.
  • Vigorous Athletic Training: How much do you workout? Do you dance or engage in sports? Vigorous exercise or athletic training can cause amenorrhea.
  • Hormonal Imbalance: You could have a hormonal imbalance. Polycystic ovarian syndrome is a common form of hormonal imbalance which may cause amenorrhea, as well as other symptoms that can include the other extreme with excessive bleeding (menorrhagia).
  • Thyroid Disease: Have you had your thyroid checked? Millions of Americans have undiagnosed thyroid disease and it is another possibility that should be explored by your physician. An overactive thyroid gland can cause missing menstrual periods.
  • Chronic Illness: If you have a chronic illness, or have been sick for an extended period, your menstrual cycle may be temporarily delayed. Once your body is well your period will usually return.
  • Pituitary Tumor (rare): Although rare, a pituitary tumor (a usually benign tumor) can cause an overproduction of prolactin which can interfere with the regulation of your menstrual cycle.

When to See Your Doctor

If you have missed three or more menstrual cycles, and you haven't already sought professional medical advice, it's time to do so to determine the underlying cause. Only a qualified healthcare provider can determine the cause of amenorrhea. You should also be alert to other signs that signal a need for medical attention. These signs include:

  • Headaches
  • Hair loss
  • Vision changes
  • Breast secretions or milk production

Your doctor has several choices for diagnosing the cause of amenorrhea. He will do a pregnancy test to be sure that isn't the cause. He will check hormone levels via blood tests, including thyroid stimulating hormone.

He can do a progestin challenge with 7 to 10 days of medication to see if it triggers bleeding. This will tell him if menstruation stopped because of a lack of estrogen. Pituitary tumors can be detected with diagnostic imaging equipment.

How the absence of menstruation is treated depends on the cause. The treatment can be as simple as lifestyle changes (diet, exercise, stress reduction), or can include hormone replacement therapy, as well as other medications when appropriate.


Absent Menstrual Periods—Secondary. MedlinePlus. https://medlineplus.gov/ency/article/001219.htm.

Menstrual Disorders. Healthywomen.org. http://www.healthywomen.org/condition/menstrual-disorders.

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