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Irregular periods can mean changes in the gap between periods, missed periods or a pattern that differs from your usual one. Pregnancy is one possible reason for a late period, but stress, contraception and several health conditions can also affect your cycle.
Start by checking whether pregnancy is possible and whether you have warning symptoms. Then keep a record of the changes. This guide explains practical next steps without assuming that every late period has the same cause.
Late periods: when to seek urgent help
Possible pregnancy with pain or bleeding needs prompt advice. The NHS ectopic pregnancy guidance advises assessment for a combination of symptoms such as lower abdominal pain, unusual bleeding or shoulder-tip pain when pregnancy is possible. Seek help even if you have not had a positive pregnancy test.
Sudden, severe abdominal pain with marked dizziness or fainting can signal an emergency. Contact your local emergency service or go to an emergency department immediately. Do not wait for another home pregnancy test.
MedlinePlus also advises contacting a clinician for bleeding that soaks a pad or tampon every hour for two to three hours. Severe pain, fever with lower abdominal pain, or bleeding that causes weakness or lightheadedness also needs prompt assessment.
First step: check pregnancy-test timing
According to the NHS, most home pregnancy tests can be used from the first day of a missed period. If you do not know when your next period is due, test at least 21 days after the last unprotected sex.
Follow the kit instructions. Testing too early can give a negative result when you are pregnant. If the result is negative but pregnancy still seems possible, repeat it after a few days. Speak to a clinician if a second test is negative and your period has not arrived.
Hormonal contraception does not stop a pregnancy test working, and no contraceptive method is completely effective. A late period should not be dismissed solely because you use contraception.
What counts as irregular periods?
The menstrual cycle runs from the first day of one period to the day before the next. This is different from the number of days you bleed. A 28-day cycle is an average, not a requirement.
The NHS describes gaps shorter than 21 days or longer than 35 days as irregular. Your age, contraception and usual pattern matter too. Periods are more likely to vary when they first start and near menopause.
A new change in your own pattern can still be worth discussing even if the numbers look reassuring. Also record bleeding between periods, after sex, or bleeding that lasts longer than usual.
Common reasons for irregular or missed periods
The NHS lists several possible causes. The following table is a guide to discussion, not a way to diagnose yourself.
| Contributor | Useful context to record |
|---|---|
| Pregnancy | Timing of tests and whether pregnancy is possible. |
| Stress | Recent pressures and changes in your daily routine. |
| Weight changes or high exercise levels | Recent weight, eating and training changes. |
| Hormonal contraception | The method and when you started or changed it. |
| Breastfeeding | Recent birth and your feeding pattern. |
| Perimenopause | Cycle changes and other symptoms during the menopause transition. |
| Hormonal or medical conditions | Other symptoms and any known diagnoses. |
Do not decide that stress or body weight must explain a missed period without considering other causes. Avoid crash dieting or increasing exercise to try to force your cycle to change. Tell your clinician if eating or training feels difficult to manage.
PMOS, formerly called PCOS
You may know this condition as polycystic ovary syndrome, or PCOS. In May 2026, an international effort introduced the name polyendocrine metabolic ovarian syndrome (PMOS). Monash University explains the change and the transition period, so both names may appear in health information.
The new name reflects broader hormonal and metabolic effects. It also corrects the misleading idea that this condition is simply caused by ovarian cysts. Irregular ovulation can be part of the condition, but one late period or an ultrasound image alone does not establish the diagnosis.
Discuss cycle changes alongside symptoms such as unwanted facial hair or acne. Your clinician can assess whether PMOS/PCOS or another explanation fits, and discuss treatment according to your needs.
Thyroid disease and other health conditions
The NHS identifies both overactive and underactive thyroid conditions among possible causes of missed periods. Tell your clinician about associated symptoms and existing diagnoses. Treatment should address the cause; there is no single tablet or supplement that suits every irregular cycle.
Primary ovarian insufficiency is not the same as menopause
NICHD describes primary ovarian insufficiency (POI) as ovaries not working normally before age 40. Periods may become irregular or stop, but some people with POI still have periods and can become pregnant.
This differs from assuming that all ovarian function has permanently ended. If your periods stop or change substantially before age 40, seek assessment rather than labelling it early menopause yourself.
When to book an appointment
The NHS advises a medical review if you miss three periods in a row, your periods have not started by age 15, or a missed period comes with other symptoms. You can seek advice sooner if you are worried or your pattern has changed.
Also discuss irregular periods, bleeding between periods, bleeding after sex, bleeding lasting more than seven days, or difficulty becoming pregnant. Do not wait for three missed cycles when there are warning symptoms.
Bleeding after menopause needs checking. The NHS advises assessment even if it happens only once, is just spotting, or occurs without other symptoms. This means bleeding after you have had no periods for at least 12 months. Do not assume it is a normal return of your cycle.
How to track irregular periods
A private diary or app can help you prepare for a visit. Record the first day and last day of bleeding, the next period’s start, and any bleeding between periods. MedlinePlus recommends noting flow and associated symptoms.
- Note how often you change menstrual products and whether they are soaked.
- Record pain, dizziness, fever or other symptoms.
- Include pregnancy-test dates and results.
- List medicines, supplements, contraception and recent changes.
- Describe how the symptoms affect work, school, sleep or activities.
For example, “bleeding started on 2 March, lasted eight days and required hourly pad changes on day two” is more useful than “my periods are abnormal.” You do not need months of records before seeking care.
What assessment and treatment may involve
Depending on your history and symptoms, a clinician may consider pregnancy testing, blood counts or iron levels, thyroid tests and an ultrasound. MedlinePlus describes these options for abnormal bleeding. Not everyone needs every test.
Treatment depends on the reason for the change and whether you want pregnancy. The NHS explains that hormonal treatments may be appropriate in some situations, while a thyroid condition needs its own treatment. Do not start hormone tablets or stop contraception without advice.
Stress support may also be useful when relevant. Our anxiety symptoms guide explains when to seek help. However, support for stress does not replace assessment of unexplained bleeding or missed periods.
A practical next step
If your period is late, check pregnancy-test timing and look for urgent symptoms first. If changes persist or concern you, arrange an appointment and bring your notes. The aim is to find the cause and a suitable plan, rather than force every cycle to last exactly 28 days.
About this information
HealthyCura shares health and wellness information for general reading. This article does not replace professional medical advice, diagnosis or treatment.
