Causes of Heavy Periods, Long Periods and How to Stop Them

Heavy periods are very common, and they are not something you simply have to put up with. Bleeding that soaks through protection, disrupts your day or leaves you exhausted can usually be reduced with the right treatment, and checking for a cause is an important first step.

This guide explains what counts as a heavy period, why your period may be heavy, including suddenly heavy this month or with clots after 40, the treatments that work and when to get help.

Quick answer

Common causes of heavy periods include fibroids, polyps, adenomyosis, endometriosis, PCOS, an underactive thyroid, the copper coil, blood-thinning medicines and the perimenopause, although often no cause is found. A period counts as heavy if you change protection every one to two hours, pass clots larger than about 2.5 cm or bleed for more than seven days. The hormonal coil and tranexamic acid can greatly reduce bleeding.

What counts as a heavy period?

• Changing a pad or tampon every one to two hours, or using two types of protection together
• Passing blood clots larger than about 2.5 cm
• Bleeding through to clothes or bedding
• Periods lasting more than seven days
• Avoiding work, exercise or social plans because of bleeding
• Feeling tired, short of breath or dizzy during or after periods

The medical term for heavy periods is menorrhagia, or heavy menstrual bleeding.

Causes of heavy periods: why is my period so heavy?

In around half of people with heavy periods, no specific cause is found. Common causes include:

• Fibroids, non-cancerous growths in or around the womb
• Endometrial polyps, small growths in the lining of the womb
• Adenomyosis and endometriosis, often with painful periods. See how endometriosis is diagnosed
• PCOS, which can cause infrequent but heavy periods
• An underactive thyroid. See underactive thyroid symptoms
• The copper coil, especially in the first few months
• Medicines that thin the blood, such as anticoagulants
• Bleeding disorders, particularly if periods have been heavy since they started
• The perimenopause, when cycles become less predictable
• Rarely, cancer of the womb lining, which is why bleeding between periods or after the menopause should always be checked

Why is my period heavier than normal this month?

A one-off heavy period is often caused by a cycle where you did not ovulate, which can happen with stress, illness, weight change or the perimenopause. Stopping hormonal contraception can also bring heavier periods. If there is any chance you could be pregnant, a heavy bleed could be an early miscarriage, so take a pregnancy test and seek advice. If heavy periods continue for more than a couple of cycles, see your GP.

Long periods: bleeding for more than seven days

A period usually lasts between two and seven days. Bleeding that regularly goes on for longer than seven days counts as heavy menstrual bleeding, even if the flow is not especially heavy each day, and it is worth seeing your GP.

Long periods share many of the causes of heavy periods, including fibroids, polyps, adenomyosis and the perimenopause. Hormonal contraception such as the implant, the injection or the progestogen-only pill can also cause longer or irregular bleeding, particularly in the first few months. Long bleeds can lower your iron, so look out for tiredness and breathlessness.

To shorten long periods, your GP may suggest the same treatments used for heavy periods, such as the hormonal coil, tranexamic acid or hormonal tablets, once any cause has been checked. Noting how many days you bleed each cycle helps them decide.

Heavy periods with clots after 40

Heavier periods and clots are common in the perimenopause, as hormone levels fluctuate. Fibroids and adenomyosis are also more common in your 40s. Small clots are normal, but regularly passing large clots, flooding, or bleeding between periods or after sex should be checked by your GP, who may arrange an ultrasound scan. See how long the menopause lasts.

How to stop heavy periods

There is no safe way to stop a period instantly, but heavy bleeding can be reduced significantly. Treatments your GP may offer include:

• The hormonal coil (LNG-IUS). The first choice for many people, it can greatly reduce bleeding and lasts several years.
• Tranexamic acid. Tablets taken during your period that help the blood clot and reduce flow.
• Anti-inflammatory medicines, such as mefenamic acid or ibuprofen, which reduce both bleeding and pain.
• The combined pill or progestogen tablets.
• Procedures, such as removing polyps or fibroids, endometrial ablation, or, if other treatments have not helped, hysterectomy.

What you can do

• Keep a diary of how often you change protection, clots and how many days you bleed
• Eat iron-rich foods such as red meat, beans, lentils and dark green vegetables
• Ask your GP for a blood test if you feel tired, breathless or dizzy
• Use heat and gentle movement to ease cramps
• Period pants and menstrual cups can help with heavy flow

When to seek medical help

Call 999 if you have:

• Very heavy bleeding with fainting, chest pain, breathlessness or a racing heart
• Heavy bleeding with severe tummy pain when you are, or could be, pregnant

Get same-day medical advice, from your GP or NHS 111, if:

• You are soaking through a pad or tampon every hour for more than two hours
• You feel dizzy or faint during your period
• You might be pregnant and are bleeding heavily

See your GP if:

• Heavy periods affect your daily life or have changed recently
• You bleed between periods, after sex or after the menopause
• You feel tired or short of breath, which may mean low iron
• You have pelvic pain or pressure

Frequently asked questions

Are blood clots in my period normal?

Small clots are normal, especially on heavier days. Frequent clots larger than about 2.5 cm suggest heavy bleeding worth checking. Treatments that reduce heavy bleeding, such as tranexamic acid and the hormonal coil, usually reduce clots too.

Can heavy periods cause anaemia?

Yes. Heavy periods are the most common cause of iron deficiency anaemia in women, causing tiredness, breathlessness and pale skin. See ferritin levels explained.

Does ibuprofen help heavy periods?

Anti-inflammatory medicines such as ibuprofen can reduce bleeding as well as pain, if they are suitable for you.

Can I take something to stop my period?

Once a period has started, medicines usually make it lighter rather than stop it. A GP can prescribe tranexamic acid or an anti-inflammatory medicine such as mefenamic acid or naproxen to reduce the bleeding. To delay a period, for example for a holiday, a GP can prescribe norethisterone if it is suitable for you. Some people taking the combined pill can take packs back to back, after checking with a GP, nurse or pharmacist.

Can stress cause heavy periods?

Stress can disrupt ovulation, which can lead to an irregular and sometimes heavier period.

Menstrual health support in Chiswick

Menstrual health is supported at Omnia Lifestyle, 8 to 9 Bedford Corner, The Avenue, Chiswick W4 1LZ, close to Turnham Green station, on bus routes 94, E3 and 272. Limited parking is available on request when booking. We can arrange blood tests for iron, ferritin, thyroid and hormones and share them with your GP, and offer acupuncture, yoga and Ayurvedic guidance alongside your medical care, passing anything that needs investigation to your GP.

An iron and ferritin blood test needs no GP referral, and an Omnia practitioner goes through your results with you. Acupuncture sessions are £80 for 60 minutes.

Read more about menstrual disorders and endometriosis and adenomyosis, see how to stop period pain fast, irregular periods and why you may be tired all the time, explore blood tests, acupuncture and yoga, or book an appointment.

This article is general information, not medical advice. If you have any of the warning signs listed above, seek medical attention.