Why Do My Periods Come Early? Exploring Common Causes and Solutions

Starting your period early can be due to stress, weight changes, exercise, hormonal shifts, or medicines. See a doctor if cycles change often.

Common causes

• Stress.
• Weight change.
• Heavy exercise.
• Hormonal birth control.
• Thyroid or PCOS.
• Perimenopause.
• Pregnancy (implantation bleeding).

Normal cycle

21 to 35 days.

What to do

Track your cycle in an app.

See a doctor

If periods are frequently early, very heavy, or irregular for several months.

Normal cycle length

A menstrual cycle counted from the first day of one period to the first day of the next is typically 21 to 35 days in adults, and 21 to 45 days in teens. A period that comes up to a week earlier or later occasionally is within normal variation.

Common causes of early periods

• Stress.
• Changes in exercise or weight.
• Perimenopause, with cycles that become shorter at first.
• Starting or stopping hormonal birth control.
• Breakthrough bleeding from an IUD or birth control pill.
• Thyroid conditions.
• Polycystic ovary syndrome.
• Pregnancy complications such as implantation bleeding or early miscarriage.
• Uterine fibroids or polyps.
• Infections.
• Travel or changes in sleep schedule.

Spotting versus a period

Light bleeding before the expected date may be spotting, not a full period.

When to take a pregnancy test

If you could be pregnant and bleeding is lighter or different from usual, take a pregnancy test.

What to do

• Track cycle dates and symptoms in an app or calendar.
• Use a pad or tampon as needed.
• Keep a record of flow, pain and other changes.

Teens

Cycles are often irregular for the first 2 to 3 years after periods begin.

See a doctor if

Periods come more often than every 21 days, bleeding is very heavy (soaking a pad or tampon every hour for several hours), cycles are consistently irregular, you have severe pain, bleed between periods or after sex, have fever, or are pregnant with bleeding or pain.

Cycle ranges and causes

The usual adult menstrual cycle is 21 to 35 days from the first day of one period to the first day of the next, and 21 to 45 days is normal for teens. A period before day 21 is considered early, and an occasional shift of a few days is common. Stress, intense exercise, weight changes, travel, illness, thyroid disease, polycystic ovary syndrome, perimenopause, starting or stopping hormonal birth control and an early ovulation can all shorten a cycle. Light bleeding mid cycle may be ovulation spotting, and light spotting after conception is implantation bleeding.

What to do

If a period comes early and you have had unprotected sex, take a pregnancy test. Track cycle dates in an app. See a doctor if periods are frequently shorter than 21 days, very heavy, last over 7 days, come with severe pain, or if you have bleeding between periods or after sex. Girls in the first year or two after menarche often have irregular cycles, which usually settle. Blood tests may check thyroid function and hormones.

Based on data from ACOG and the Mayo Clinic