Why is my period late? 8 common reasons

Eight common reasons a period runs late

1. 01

   You could be pregnant

   The most important one to rule out first if you're sexually active. A home test is most reliable from the day your period was due, and more so a few days later. If it's negative but your period still hasn't come after a week, test again or see a clinician.

2. 02

   Stress

   High or prolonged stress raises cortisol, which can delay or suppress ovulation and push your period back. A single stressful stretch — exams, a move, illness in the family — is a common one-off cause.

3. 03

   Big changes in weight or eating

   Rapid weight loss, very low calorie intake, or a jump in weight can all disrupt the hormones that drive your cycle. Under-eating relative to your activity is a frequent, and reversible, cause.

4. 04

   A hard training block

   A sudden increase in intense exercise — marathon training, a new sport — can delay or stop periods, especially if you're not eating enough to match the effort.

5. 05

   Thyroid or other hormonal shifts

   An under- or over-active thyroid can lengthen or shorten cycles. It's checkable with a simple blood test, so it's worth raising if late periods keep happening alongside tiredness, weight changes or temperature sensitivity.

6. 06

   PCOS

   Polycystic ovary syndrome commonly causes irregular or infrequent periods because ovulation happens less predictably. If late or skipped periods come with acne, extra hair growth or difficulty conceiving, mention PCOS to your clinician.

7. 07

   Perimenopause

   From your early 40s — sometimes late 30s — cycles naturally become less regular as you approach menopause. Late periods that arrive alongside hot flushes, sleep changes or mood shifts may be part of that transition.

8. 08

   Contraception and recent hormonal changes

   Starting, stopping or switching hormonal contraception can shift your cycle for a few months. Cycles often take a little while to settle into their own rhythm again afterwards.

Common questions

How late is actually 'late'?

A typical cycle is anywhere from 21 to 35 days, and a few days' variation month to month is normal. A period is usually considered late once you're past the length of your own longest recent cycle. One late cycle is rarely a concern; a pattern is more telling.

When should I take a pregnancy test?

If there's any chance you're pregnant, test from the day your period is due — a few days later is more reliable. Retest in a week if it's negative and your period still hasn't arrived.

How does tracking help?

Knowing your own usual cycle length is what tells you whether a period is genuinely late. A record of recent cycles and symptoms also gives a clinician far more to work with than 'it feels off'.

When should I see a doctor?

See a clinician if you miss three or more periods in a row, if periods become consistently irregular, if you have late periods alongside other symptoms (pain, unusual discharge, hot flushes), or if you're trying to conceive and cycles are unpredictable.

Keep reading

Menopause transition

Am I in perimenopause? 8 early signs

Mood & PMDD

PMDD vs PMS: how to tell the difference

Flow & bleeding

Is my period too heavy? When to see a doctor