Most late periods turn out to be nothing. What to do next depends almost entirely on whether pregnancy is possible for you this cycle.
How late can a period be and still be normal?
A period can be as late as ovulation was. A cycle has two halves, and they aren’t equally flexible. The stretch after ovulation holds at around two weeks. The stretch before it is the one that moves. NICHD puts ovulation anywhere from 10 to 21 days after day 1.
Three or four days late is inside normal variation for almost everyone. Five days past the day you expected it is the usual point to call a period late. A week or two late is ordinary once in a while, especially after a stressful month, an illness or travel. After six weeks with no period, count it as a missed period. Three missed in a row is the point the NHS says to see a GP.
So a late period usually means ovulation was late and the period followed it on schedule. Stress, illness, travel and a change in how much you exercise all act on that first half. A late period isn’t a sign that something is building up.
When is a period considered late?
A period is late when it’s past the longest gap your own cycles usually run to. The common rule of thumb is five days past the day you expected it. Almost nobody’s cycle is exactly 28 days every month. The NHS gives a normal range of 21 to 35 days between periods, with 28 in the middle. The NICHD at the National Institutes of Health notes teenagers can range from 21 to 45 days and still be normal. So a period arriving on day 32 is late only if your own cycles usually run to 27.
You can’t know that baseline without a record of the last several cycles. A single long cycle is also weak evidence of anything, because normal cycle length shifts by a few days from one month to the next. The NHS says the gap between your periods may vary each time, and that periods that come early or late are what having irregular cycles means. If yours came early instead, the guide to a period that came early works through the same question from the other side. If you don’t have that record yet, you can work out when your next period is due from your last start date and your usual cycle length. Past that date already? The is my period late calculator counts how many days late you are.
Count from day 1, which is the first day of real bleeding rather than spotting. Getting that day wrong by two days makes every cycle length after it wrong by two days, which is enough to invent a lateness that isn’t there.
If pregnancy is possible, test first
Pregnancy is the first cause on every clinical list of missed periods. It’s the only one where the answer changes what you do today, and the cheapest to rule out.
The NHS guidance on doing a pregnancy test says tests are most reliable from the first day of a missed period. If you don’t know when your period was due, test at least 21 days after you last had unprotected sex. Home tests detect hCG, which the body starts producing around six days after fertilisation, so testing much earlier than that gives confusing results.
A positive result is almost certainly correct. A negative result is less reliable, because it can mean you tested too early. If your period still hasn’t arrived a few days later, test again. Hormonal contraception doesn’t stop a pregnancy test working, and no method of contraception is completely effective, so being on the pill isn’t a reason to skip the test.
Why is my period late if I’m not pregnant?
Once you’ve ruled out pregnancy, the NHS list of causes of missed or late periods is short:
- Stress. The everyday kind counts. A hard month at work can move a period.
- Sudden weight loss, or being overweight. Both ends of the range disrupt the hormone signalling that starts a cycle.
- Doing too much exercise. It’s a common and often missed cause in people who’ve recently started exercising more.
- Hormonal contraception. The pill, the injection, and the IUS all change or stop bleeding by design. A late bleed means something different on them, and the guide to tracking your period on birth control explains what. If you’ve recently come off a method, a late period after stopping birth control is its own situation, and usually a slow first cycle rather than a missed one.
- Breastfeeding. Periods often stay away for months. The guide to your period after giving birth covers when it usually comes back.
- Perimenopause. This is the run-up to menopause, usually somewhere between 45 and 55. ACOG describes perimenopause as the phase where hormone levels and the cycle begin to change, and defines menopause itself as twelve months with no period. Our guide on tracking your period in perimenopause covers what the gaps look like and what to log.
- PCOS, also known as PMOS. Polyendocrine metabolic ovary syndrome is one of the most common reasons cycles go long and unpredictable.
- Thyroid and other conditions. An overactive or underactive thyroid, diabetes and heart disease can all stop periods.
Almost all of these act slowly and show up as a run of odd cycles rather than one dramatic one.
When to stop waiting and see someone
The NHS says to see a GP if:
- you’ve missed your period three times in a row
- your periods haven’t started by the time you’re 15
- you’ve missed a period alongside other symptoms such as weight gain or weight loss, tiredness, hair growth on your face, or dry or oily skin
- your periods have become irregular
NICHD defines secondary amenorrhea as an absence of more than three cycles in someone whose periods were previously regular. It also says that when pregnancy, breastfeeding or menopause isn’t the cause, a missed period generally points to something else that needs finding. A GP will usually ask about your health and may run blood tests to find the cause.
None of that means you should wait three months if something feels wrong. Severe pain, bleeding that’s much heavier than usual, or a late period alongside symptoms that worry you all call for an appointment now.
What to bring to that appointment
The single most useful thing you can hand a clinician is a list of when your last several periods started. It lets you say the last four were 29, 41, 33 and 47 days long, instead of saying your cycles feel off.
Recording it as you go beats reconstructing it afterwards, because memory keeps the alarming cycles and drops the ordinary ones. Our guide on keeping a period diary covers what to write down and what to skip. If long or unpredictable cycles are normal for you, the guides on why periods go irregular and tracking with PCOS go further.
How Plum handles a late period
We make Plum, a period tracker app for iPhone, so this part is about our own app.
Plum predicts from a rolling median of your recent cycles rather than a plain average, so one unusually long cycle doesn’t drag every prediction after it. It still shows one predicted day, and from the day after it says your period is late. Insights shows how much your cycles usually vary, as plus or minus a number of days. If that number is 5, a period 2 days past the predicted day is well inside your normal.
Plum deliberately doesn’t guess why. It won’t tell you that you’re pregnant, and it won’t diagnose PCOS or a thyroid problem. It keeps the record straight so that you, or a clinician, can see the pattern that answers the question.
Plum shows no ads and never sells personal data. It does require an account and syncs to our servers, encrypted in transit and at rest, so we won’t claim it stays on your phone. You can delete your account and everything in it from inside the app at any time. If you share a cycle with a group, the group sees your period dates, and the days you worked out if you track exercise. Your symptoms and moods stay yours. To weigh it against other apps, see our top period tracker apps, one for each need.
