A period every 2 weeks is shorter than the usual 21 to 35 day cycle. See a doctor if it keeps happening.
Normal cycle
21 to 35 days. A period every 14 days is too frequent (polymenorrhea).
Causes
- Stress.
- Hormonal birth control.
- PCOS.
- Thyroid disease.
- Perimenopause.
- Ovulation bleeding.
- Fibroids or polyps.
Track
Keep a diary of bleeding.
See a doctor
If it continues for more than a few months.
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Emergency
Very heavy bleeding or dizziness.
Cycle ranges
A normal menstrual cycle runs 21 to 35 days in adults and 21 to 45 days in teens, counted from the first day of one period to the first day of the next. Getting a period every 14 days is shorter than normal and is called polymenorrhea (cycles under 21 days).
- Causes include anovulatory cycles, perimenopause, thyroid disease, PCOS, stress, extreme exercise, uterine polyps, fibroids and infections.
- Breakthrough bleeding on hormonal birth control can resemble a period.
- Early pregnancy bleeding or an ectopic pregnancy can mimic a short cycle.

What to do
Track dates, flow and symptoms in an app or calendar for 2 to 3 months. See a doctor if cycles are under 21 days repeatedly, bleeding is heavy (soaking a pad or tampon every hour), lasts over 7 days, or comes with severe pain or dizziness. Tests include a pregnancy test, blood tests (thyroid, hormones, blood count) and pelvic ultrasound.
Cycle ranges
Normal cycles are 21 to 35 days in adults, so a period every 14 days is shorter than usual. Causes include anovulatory bleeding, stress, polycystic ovary syndrome, thyroid problems, fibroids and hormonal contraception.
What to do
Track dates and see a provider if cycles are under 21 days, bleeding is heavy or lasts over 7 days. Pregnancy tests may be useful.
Cycle length basics
A normal menstrual cycle lasts 21 to 35 days in adults and 21 to 45 days in young teens. A period every 14 days is shorter than the typical range (polymenorrhea) and can come from anovulation, perimenopause, thyroid disease, PCOS, stress, new hormonal contraception, fibroids, polyps, infection or pregnancy complications.

What to do
Track dates, flow and symptoms. See a clinician for cycles shorter than 21 days, bleeding that is heavy (soaking a pad or tampon every hour), periods lasting more than 7 days, bleeding between periods or after sex, and fatigue or dizziness. The doctor may perform a pregnancy test, blood tests (hormones, thyroid, iron) and a pelvic ultrasound. Treatment depends on the cause and may involve hormones, iron and surgery for structural problems.
Based on data from the American College of Obstetricians and Gynecologists and the Office on Women’s Health





