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Irregular periods

Dr Roger Henderson
Reviewed by Roger HendersonReviewed on 29.04.2024 | 4 minutes read

Irregular periods describe as when you can’t predict when your period will come and the length of time between periods changes every month. Most women have their own "normal" - for most this is a period every 28 days, but some women bleed every 21 days, others every 35 days - this is the range of "normal".

The number of days of bleeding may vary - most women bleed for 5 days, but between 3 and 8 days is considered normal. An app can help you keep track of your rhythm, so you can get to know what's normal for you.

Oligomenorrhoea is the medical term for infrequent periods, and can cause a great deal of anxiety and disruption. It also has consequences if you’re planning to get pregnant.

Irregular periods may coincide with heavy bleeding or painful bleeding.

Doctor’s advice

What causes irregular menstrual bleeding?

Irregular periods may have a number of causes, the most common of which are hormonal imbalances, such as perimenopause (experienced in the years approaching menopause), PCOS (polycystic ovary syndrome), or an underactive thyroid gland (hypothyroidism).

Stress is a common, but often overlooked, cause of irregular menstrual bleeding, and it can take a while to get periods back on schedule after a particularly distressing time.

Fibroids can both cause both heavy and irregular menstrual bleeding and painful periods.

You may have unpredictable vaginal bleeding that isn’t a period – superficial injuries to the vagina for example rough sex or vaginal dryness can lead to bleeding, and polyps, which are small non-cancerous growths that occur around the uterus or the endometrium and cause heavy bleeding at times. Sexually transmitted infections (STIs) such as chlamydia can cause irregular bleeding, too.

Heavy bleeding can be a sign of a miscarriage and can sometimes occur when pregnant due to complications. Pregnancy should also be on your mind if your period has come late. Periods will be disrupted after a miscarriage, abortion or birth, or any stopping or starting of contraception, so give it time and hopefully you’ll get back on track within a few months.

Contraceptives such as the copper coil (intrauterine device) or the mini pill (progestogen-only pill), this is also common in the first few months of starting any hormonal contraceptive. The contraceptive implant and injection, both containing progestogen, typically cause much lighter periods or no periods, but some women report irregular periods or unpredictable spotting.

The emergency pill, which is a high dose of progestogen, can disrupt your following period too.

Cancer of the uterus or cervix or vagina can also cause irregular menstrual bleeding.

When should I see my doctor?

Any persistent irregular bleeding or bleeding in between your periods, especially when accompanied with pain, should be reviewed by your doctor. Bleeding during or after sexual intercourse should also be discussed with your doctor.

Irregular bleeding can cause difficulty getting pregnant as ovulation is not happening regularly - if you are struggling with this, particularly if you and your partner have been trying regularly for at least a year, you should book an appointment with your doctor. 

What will my doctor do?

Your doctor will ask about your symptoms, and they may offer an examination of your vaginal area to see if there are any abnormalities that may be causing your symptoms. With your permission, this may be with an instrument called a speculum, to visualise the vaginal passage, and an internal exam, to feel for any masses or pain around the pelvic organs.

If your smear test is due, they can arrange for this.

They may suggest blood tests to check for hormonal imbalances, including thyroid tests and PCOS tests, and they will check for anaemia. If you are trying to get pregnant or may be experiencing menopause, they may request a particular set of hormones. Your doctor will take vaginal swabs to check for STIs.

A pelvic ultrasound scan can check for polycystic ovaries, fibroids, endometriosis or adenomyosis and other causes.

If the cause is unclear and the symptoms persist, the GP may need to refer to the gynaecologist for further investigations. This will happen urgently if they think there’s any chance this could be due to cancer.

What's the treatment?

Symptoms and treatment are managed according to the cause. If stress is a cause or contributing factor, you and your doctor may, together, consider how to introduce stress reduction techniques.

If your type of contraception is thought to be contributing, together you and your doctor can consider whether the irregular bleeding is worth continuing treatment, or whether you wish to switch contraceptive methods.

The combined oral contraceptive pill can be used to regulate periods and simple painkillers can be taken for the pain. Infections are usually treated with antibiotics.

For problems such as PCOS, fibroids or endometriosis, you may be referred to a gynaecologist to consider medications or surgery. Fibroids management depends on the size and position- and they can be managed without any treatment, with medication or surgically. Endometriosis is managed according to the symptoms and the complications.

Concern regarding cancer requires urgent referral to a specialist, and they will take it from there.

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Dr Roger Henderson
Reviewed by Roger Henderson
Reviewed on 29.04.2024
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