Periods
Irregular periods
Periods that come unpredictably, too often, too rarely, or with cycles that vary in length, which can be a normal variation but can also reflect a hormonal condition worth investigating.
Education and reference only. This explains the common causes of irregular periods and the warning signs that need urgent help, in plain language — it is not a diagnosis or a substitute for advice from a clinician. If you feel very unwell or are worried, seek medical help.
Quick answer
What is irregular periods?
A typical menstrual cycle settles into a fairly regular pattern, though it is normal for cycle length to vary somewhat from month to month. Periods are considered irregular when the gap between them keeps changing, when they come much more or less often than usual, or when they stop and start unpredictably.
- Get urgent help: Seek urgent help if you have heavy bleeding that soaks through pads or tampons every hour, with dizziness or feeling faint. See a doctor promptly for bleeding after sex, bleeding between periods, or any bleeding after the menopause.
- Self-care: Keeping a simple record of your cycles — when periods start, how long they last and how heavy they are — gives you and your clinician a clear picture and can reveal a pattern behind apparent irregularity.
About irregular periods
A typical menstrual cycle settles into a fairly regular pattern, though it is normal for cycle length to vary somewhat from month to month. Periods are considered irregular when the gap between them keeps changing, when they come much more or less often than usual, or when they stop and start unpredictably. Irregular periods are very common in the years after periods first begin and as the menopause approaches, and they can also follow stress, significant weight change, intense exercise or starting and stopping hormonal contraception. Persistent irregularity, though, can be a sign of a hormonal condition. Polycystic-ovary-syndrome is a frequent cause, often with other features such as acne and excess hair, while thyroid problems — both an underactive (hypothyroidism) and overactive (hyperthyroidism) gland — can disturb the cycle. A raised level of the hormone prolactin, hyperprolactinaemia, can also make periods irregular or stop them. Working out the pattern helps decide whether investigation is needed.
When to get help
Call 999 or go to A&E if irregular periods comes with any of these warning signs:
- Seek urgent help if you have heavy bleeding that soaks through pads or tampons every hour, with dizziness or feeling faint.
- See a doctor promptly for bleeding after sex, bleeding between periods, or any bleeding after the menopause.
- See a doctor if periods stop for several months and pregnancy is not the reason.
- Seek advice for irregular periods with milk leaking from the breasts, headaches or changes in vision.
- See a doctor for irregular periods alongside marked weight change, a racing heart, or feeling unusually hot or cold.
When to see a doctor
See a doctor if your periods are persistently irregular, if the pattern has changed noticeably, or if irregularity comes with other symptoms such as acne, excess hair growth, weight change, tiredness, or a racing heart, as these can point to a hormonal cause that can be confirmed and managed. You should also be seen if periods stop for several months without pregnancy, if you bleed between periods or after sex, or if there is any bleeding after the menopause, as these need assessment. Tracking your cycles before the appointment helps your clinician greatly. If you are trying to conceive and periods are irregular, it is worth seeking advice sooner.
Not sure how urgent it is? It is always OK to call NHS 111 for advice, day or night.
What can cause it
Common causes of irregular periods
Irregular periods has many possible causes. Each links to a full, plain-language guide to that condition — what it is, how it's treated and when to seek help.
What helps
Self-care and what you can do
Keeping a simple record of your cycles — when periods start, how long they last and how heavy they are — gives you and your clinician a clear picture and can reveal a pattern behind apparent irregularity. Looking after general health often helps the cycle settle: aim for a balanced diet, regular activity, a healthy weight, and steady sleep, and try to manage stress, since significant stress, very intense exercise and large weight changes can all disturb periods. If you have recently started or stopped hormonal contraception, some irregularity for a few months can be expected. None of this replaces assessment when periods are persistently irregular, but tracking and healthy habits give the best foundation while the cause is sorted out.
Answers
Irregular periods: frequently asked questions
What counts as an irregular period?
Periods are irregular when the gap between them keeps changing, when they come much more or less often than usual, or when they are unpredictable. Some variation in cycle length is normal, but a persistently changing pattern is worth discussing.
What commonly causes irregular periods?
Common causes include the years after periods begin and around the menopause, stress, weight change, intense exercise, and starting or stopping hormonal contraception. Persistent irregularity can point to conditions such as polycystic ovary syndrome, thyroid problems or a raised prolactin level.
When should I see a doctor about irregular periods?
See a doctor if irregularity is persistent or new, if periods stop for several months without pregnancy, if you bleed between periods or after sex, or if there is bleeding after the menopause. Also seek advice if there are other symptoms such as weight change or a racing heart.
Can stress and weight affect my periods?
Yes. Significant stress, large changes in weight, and very intense exercise can all disturb the menstrual cycle. Looking after general health and managing stress can help the cycle settle, but persistent irregularity still deserves assessment.
Sources
Where this is drawn from
- NICE CKS: Amenorrhoea.
- Royal College of Obstetricians and Gynaecologists
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