Late period
A period is described as late when it does not arrive on the expected date. A few days' shift happens to everyone and almost never means anything, but no…
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Medicines commonly prescribed for Late period
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A period is described as late when it does not arrive on the expected date. A few days' shift happens to everyone and almost never means anything, but no period for a week or more is a reason to look into the cause. Most often it is harmless, though some causes need treatment — and the first thing to rule out with a late period is pregnancy.
What counts as normal
A cycle usually runs from 21 to 35 days, counted from the first day of one period to the first day of the next. A variation of a few days from month to month is normal. Worth remembering as well: in the first year or two after periods begin, and as menopause approaches, the cycle is irregular by nature, and that is not a disorder.
Common causes
- Pregnancy — the first thing to exclude with a late period if you are sexually active;
- stress, poor sleep, changing time zones — the hypothalamus is sensitive to strain and shifts the cycle easily;
- abrupt weight change in either direction, strict diets, intense training;
- polycystic ovary syndrome — one of the most frequent causes of persistent irregularity, usually alongside excess hair growth, acne and difficulty conceiving;
- thyroid disease — both reduced and increased function disturb the cycle;
- raised prolactin, sometimes with discharge from the nipple;
- hormonal contraception, its start or withdrawal, and hormonal coils;
- breastfeeding;
- perimenopause — generally after 45;
- certain medicines: antidepressants, antipsychotics, epilepsy drugs, chemotherapy.
When to see a clinician
- you have missed three cycles in a row and pregnancy is excluded;
- your cycle is shorter than 21 days or longer than 35, and has been for several months;
- periods have become heavy, last more than a week, or come with severe pain;
- there is bleeding between periods, after sex, or after menopause has arrived;
- the irregularity coincides with weight change, facial hair growth, acne, nipple discharge or constant tiredness;
- periods have not started by the age of 15 or 16;
- you are trying to conceive and have not managed within a year.
What happens at the appointment
The clinician will ask about the pattern of your cycle, your weight, physical activity, medication and any plans for pregnancy. A pregnancy test is usual, along with blood tests for thyroid hormones and prolactin and, where polycystic ovary syndrome is suspected, sex hormones and a pelvic ultrasound.
It is a great help to arrive with at least 3 to 6 months of data: the start date of each period, how long it lasted and how heavy it was. A tracking app works just as well as notes in a diary.
Treatment
What is treated is the cause, not the delay itself. With thyroid disease the cycle re-establishes once hormones are corrected. In polycystic ovary syndrome the approach depends on the goal: if pregnancy is not planned, combined contraceptives are often used to give regular bleeds and control symptoms; if it is, medication to stimulate ovulation. In perimenopause, menopausal hormone therapy is discussed. And where the cause lies in stress, excessive exercise or being underweight, the main treatment is restoring rest, sleep and nutrition.
Common questions
Does an irregular cycle mean infertility? No, though it makes timing ovulation harder. Many causes of irregularity are treated successfully.
Can you get pregnant with an irregular cycle? Yes. Ovulation may happen unpredictably, so irregularity is not a method of contraception.
My cycle shifted after an illness or a flight — is that a problem? A one-off shift after strain, an infection or a change of climate usually settles on its own within one or two cycles.
Online consultation
In an online appointment a doctor can review your cycle, work out which causes to check first, advise which tests to start with and explain whether an in-person gynaecology or endocrinology appointment is needed.
This article is for general information and does not replace a consultation with a doctor.
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Reviewed on Jul 10, 2026
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