How does the late period checker work?
- Your period is due on your last start date plus your usual cycle length.
- We allow a few days either side as normal variation (a week if your cycles are irregular), because even regular cycles move.
- If you could be pregnant, the NHS says most tests work from the first day of a missed period.
- If your periods stop for 3 months or more and you're not pregnant, the NHS suggests seeing a GP.
Common reasons a period is late
Pregnancy is one, so if there's a chance, test. Others include stress, illness, travel and jet lag, big changes in exercise or weight, breastfeeding, coming off hormonal contraception, PCOS, thyroid problems and perimenopause (NHS). Ovulating later than usual is the most common reason a single period arrives late.
Read more in late period: common reasons, or check timing with our pregnancy test timing tool.
When to see a doctor
- Your periods have stopped for 3 months or more and you're not pregnant.
- Your cycle is often shorter than 21 days or longer than 35, or changes by more than 20 days.
- You're pregnant or might be and have one-sided pain, bleeding, shoulder-tip pain or feel faint: get urgent help.
In the UK you can call NHS 111 for advice, any time. In an emergency call 999 (UK) or 911 (US).
Questions people ask
How late can a period be before I worry?
A few days either way is common. Stress, illness, travel, weight change, exercise and some medicines can all delay a period. If you could be pregnant, take a test. If your periods stop for 3 months or more, see a GP.
Can stress make my period late?
Yes. Stress can delay ovulation, and a later ovulation means a later period. Illness, jet lag and big changes in sleep can do the same.
My test was negative but my period is still late.
You may have tested early. Test again in a few days with first-morning urine. If it's still negative and your period hasn't come, talk to a GP or sexual health clinic.
Is a late period a sign of PCOS?
One late period usually isn't. Cycles that are often longer than 35 days, or fewer than 8 periods a year, are worth mentioning to a GP. Our PCOS signs check explains what doctors look for.
Is anything I enter saved or sent?
No. Everything runs in your browser. Nothing is stored or sent, and the page makes no network requests when you use it.
Sources
Written by the Splash team · Sources checked Oct 2026 · Updated
