Reviewed December 2019

How to figure out the cause of your heavy periods


For the majority of women, periods are an inconvenience, but bearable, and don’t cause any major problems. A normal menstrual cycle can last anything from 21 to 40 days,1 with between two and seven days of bleeding each cycle.

Having heavy periods is one of the most common reasons for women to be referred to a gynaecologist, with 5% of women aged 30-49 years consulting their GP due to heavy bleeds each year.2 This doesn’t mean something is wrong, however, and in fact it can be completely normal. If excessive, though, heavy bleeding can be something that can have a significant emotional impact on those affected by it.

The average blood loss during a period is less than an egg cup full (30-40ml). Historically, excessively heavy periods (menorrhagia) was defined as more than 80 ml of blood loss over the course of the period. More recent recommendations now state that menorrhagia should actually be determined by the woman who has it rather than by an arbitrary figure. For this reason it is now classed as excessive blood loss that interferes with a woman’s physical, social, or emotional quality of life, rather than any single amount.3

Who should you seek advice from if something is wrong?

If you suffer from excessively heavy periods it may be useful to ask yourself: “Is the bleeding greater than I can reasonably manage?” If the answer to this is yes, please see your doctor and don’t suffer in silence. There are several treatments available that can make a difference to your symptoms.

It is also important to see your doctor if your periods suddenly change or are accompanied by new features such as bleeding in between your periods or after sex. You should also see your doctor if you are bleeding and think that there is any chance you may be pregnant.

What could the cause of my heavy periods be?

Menorrhagia can be caused a number of different factors, but for almost 50% of women with menorrhagia, no obvious medical cause can be found.4 When no specific reason is found, this is known as dysfunctional uterine bleeding (DUB).5

Other causes of menorrhagia can include: endometriosis, fibroids, endometrial polyps, and polycystic ovarian syndrome. Sometimes your other symptoms (alongside heavy bleeding) can be indicative of the underlying cause. We have taken a look at these secondary symptoms below to help you better understand what the cause of your heavy periods could be, and to give you advice on what else may be worth discussing with your doctor.


Unfortunately, period pain can be a normal part of having periods, but if it becomes severe and is accompanied by heavy bleeding it may be caused by endometriosis in some women.6 If you also suffer from bloating, blood in your stools, or deep pain when you have sex (dyspareunia), these can also point towards the same diagnosis.

Endometriosis occurs where the cells that normally line the uterus start to grow in other locations as well. These cells are then shed each month, in a similar way to tissue in the uterus. It is this that causes intense pain. This tissue may be found in all sorts of locations including in your ovaries, bowel, and the tissues lining your pelvis. The symptoms experienced are dependent on the locations of the endometriosis, but often women with endometriosis experience heavy and painful periods.

Another related condition that may present similarly is adenomyosis. This is where the tissue that normally lines the womb starts to grow in inside the womb wall, and it can also result in especially painful periods.

Irregular periods

Women with irregular periods often find that they may also be heavy and painful. This is because these women have more time in between their periods to thicken the lining of their womb, resulting in greater blood loss. This is a common problem in women with polycystic ovarian syndrome. Due to a complex hormonal imbalance involving high levels of androgens (male hormones) and a resistance to the hormone insulin, they often have irregular cycles that result in heavier periods.


This is a symptom that quite often may occur alongside very heavy periods. Usually, the tiredness results from an iron deficiency anaemia secondary to the blood loss. In this case, iron replacement in the form of supplements (on the advice of your doctor) can help correct the tiredness. Your heavy periods would need to be investigated as well to stop this happening again.

In addition, hypothyroidism (an underactive thyroid) can also present with tiredness, menorrhagia, and irregular periods, so your doctor may suggest doing some basic blood tests to rule this out. If hypothyroidism is found, it can be treated by taking the medication thyroxine regularly.

Weight gain or obesity

Women who have gained weight or are overweight are more likely to suffer from heavy periods too. The reason for this is increased levels of oestrogen. This hormone is produced by the ovaries and in fat cells, and is responsible for the growth and thickening of the lining of the uterus.

In women that have an increase in their levels of body fat, more oestrogen is produced. This leads to a thicker uterine lining, heavier bleeding and, often, irregular periods. Polycystic ovarian syndrome can also lead to weight gain, so a lot of these factors can overlap.

Your doctor may suggest trying to lose some weight if you can and may test your bloods to check you don’t have an underactive thyroid which can result in irregular, heavy periods, and weight gain.

Bleeding after having sex or in between your periods

If you are suffering from heavy menstrual bleeding and have bleeding between your periods or after sex, you will need to be examined and then have investigations if needed. Your doctor will examine you and check that your cervical smears are up to date. There are several possible causes of bleeding between periods including pelvic infections, an increased thickness of the womb lining (endometrial hyperplasia), or very occasionally even endometrial cancer.

If you have persistent bleeding in between your periods, a sudden change in symptoms or are over the age of 45 with heavy bleeding, it is likely you will be referred for an ultrasound of your womb and sometimes an endometrial biopsy. In most women, this will come back normal, but it is much better to be sure.

Heavy periods and cramps when you have a coil in place

If you have the IUD (copper coil) for contraception, this can cause heavy, painful periods in some women. Your doctor may suggest swapping your coil over to an IUS (Mirena coil) if this is suitable. The Mirena coil contains a small amount of the hormone progesterone and works as a contraceptive device, but also makes most women’s periods a lot lighter.7

Anovulatory cycles

If you have irregular periods, it is likely that your ovaries don’t release an egg during every menstrual cycle (anovulation). If this happens, your body does not produce as much progesterone in that cycle. The lack of progesterone means the lining of the uterus is not shed in the normal way, causing thickening. When the lining is eventually shed, it causes heavy bleeding.

Anovulatory cycles are common when girls start having periods (menarche) and towards the menopause too, resulting in heavy, irregular and often painful periods. Irregular bleeding and anovulatory cycles (where an egg is not released) are common. Longer gaps between periods means a longer time for the endometrial lining (lining of the womb) to build up and thicken.

Simple treatments can be used to lessen blood loss, and young girls who are finding their periods particularly heavy or painful may also benefit from the use of the pill to regulate their cycles for a while, on the advice of a doctor.

Sometimes, women with menorrhagia are found to have non-cancerous growths or polyps in or around their uterus, called fibroids. Often, fibroids do not need any treatment. Over time they can shrink and even disappear, especially after the menopause. However, if they are causing excessive bleeding, your doctor may suggest treatments to reduce the bleeding.

If you have heavy periods but to tend to bleed elsewhere as well

If you bruise easily, or bleed more than others if you cut yourself, your doctor may wish to check your blood clotting via a blood test. Usually, it will be fine, but certain conditions can make your blood less sticky and less likely to clot. For example, a condition called Von Willebrand disease (VWD), which needs specific treatments.

Taking certain medications can also increase your propensity to bleed as well. Medications taken to reduce the risk of your blood clotting such as those taken after you suffer a deep vein thrombosis can increase the amount of blood loss you have. These drugs include heparin, warfarin and NOACS (e.g. dabigatran).

I have heavy periods, do I need them investigated?

If slightly heavy periods are normal for you, you are up to date with your smear, and you are otherwise well, then the likelihood is that your heavy periods do not need to be extensively investigated. If your periods are getting heavier, you have new symptoms, or are over the age of 45, your doctor will probably want to investigate.

Usually, your doctor will examine you and arrange some basic blood tests. Your doctor may also send you for an ultrasound scan to identify any structural abnormalities such as fibroids or a thickened lining on the womb. You will also need a cervical smear if this is due.

How are excessively heavy periods treated?

Most women with menorrhagia can be treated effectively by their GP. Not everyone needs referral to the hospital. If you have heavy periods but there is no obvious cause, you will most likely be treated for dysfunctional uterine bleeding. Usually this starts with medication to reduce the blood loss such as tranexamic acid.8 These are tablets that are taken just before you start your period and for the first few days of your period to reduce the blood loss, and discomfort if you have any.

Other women may benefit from hormonal treatments such as the combined oral contraceptive pill or the mini pill depending on their suitability. Some women find insertion of the Mirena coil helpful to reduce bleeding, as well as for contraception.

If these simple measures do not give you the relief that you need, don’t worry, there are other treatments that can be tried, but it may well be that you are referred to see a consultant to discuss other treatment options if you have not been referred already.

Please do not suffer in silence, see your doctor and find out what can be done to help. It really could make a difference and make your symptoms easier to manage.

Featured image is of a woman lying on a sofa, covered in a blanket. Only her legs, from the knee down, are visible. The blanket is light blue and the sofa is grey

Last updated December 2019
Next update due 2022

Dr. Jennifer Kelly, MBChB(hons) MRCGP DRCOG

Jennifer is a General Practitioner, medical writer, parent, and founder of the Grace Kelly Ladybird Trust, registered charity for childhood cancer awareness and research. She also has a particular interest in women’s and children’s health, and enjoys medical writing, particularly helping make medical information easily accessible to those who want to find out more.

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  1. NHS, ‘Periods and fertility in the menstrual cycle’, NHS website, July 2016, [online], (accessed 8 December 2019)
  2. NICE, Menorrhagia, Clinical Knowledge Summary, National Institute for Health and Care Excellence, December 2018, [online],!backgroundSub:1 (accessed 9 December 2019)
  3. NICE, ‘Heavy menstrual bleeding: assessment and management’, NICE Clinical Guideline NG88, [online], 2018,, (accessed 9 December 2019).
  4. NICE, Menorrhagia, Clinical Knowledge Summary, National Institute for Health and Care Excellence, December 2018, [online],!backgroundSub:1 (accessed 9 December 2019)
  5. Pitkin, J., ‘Dysfunctional uterine bleeding’, BMJ, Vol. 26334, No. 7603, 2007, pp. 1110-1.
  6. NICE, Endometriosis,Clinical Knowledge Summary, National Institute for Health and Care Excellence, May 2014, [online],!diagnosisSub (accessed 9 December 2019)
  7. FSRH, Intrauterine Contraception, Clinical Effectiveness Unit, October 2015, [online] (accessed 9 December 2019)
  8. NICE, Menorrhagia, Clinical Knowledge Summary, National Institute for Health and Care Excellence, December 2018, [online],!scenario (accessed 9 December 2019)

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