Heavy periods: how to tell, what causes them, and what helps

Reviewed by Emma Carter, Senior Health & Nutrition Editor

Almost nobody measures their menstrual blood loss, and the clinical definition that used to be quoted, more than 80 mL a period, was never something a woman could apply to herself. So the practical question is not how many millilitres. It is whether your periods are shaping your week.

This guide covers when bleeding needs urgent help, how to tell whether yours counts as heavy, what is usually behind it, and why heavy periods sit at the center of so much tiredness.

When bleeding needs help sooner

Most heavy bleeding is not an emergency, and the table below is mostly about not waiting rather than about panic. The first row is the exception.

If this is happening	What to do
You could be pregnant and you have heavy bleeding, soaking a pad soon after putting it on, or severe tummy pain, pain in your shoulder, or you feel sick, faint or dizzy	Call 999. The NHS names these as signs you need immediate treatment (NHS)
Any bleeding at all once your periods have stopped for good	See a GP. It is not usually serious, but it always needs checking, and you should not have to wait more than two weeks to see a specialist (NHS)
Bleeding between periods or after sex, severe period pain, or pain when peeing, pooing or having sex	See a GP rather than waiting to see whether it settles (NHS)
Heavy periods that are affecting your life, or that have gone on for some time	Book an appointment. You do not need to have exhausted every self-help option first

Is yours actually heavy?

The NHS uses signs you can recognize without a measuring jug. You may have heavy periods if you (NHS):

• Need to change a pad or tampon every one to two hours, or empty a cup more often than it is designed for
• Need two types of period product together, for example a tampon and a pad
• Have periods lasting more than seven days
• Pass blood clots larger than about 2.5 cm, roughly a 10p coin
• Bleed through to your clothes or bedding
• Avoid things you would otherwise do because of your period
• Feel tired or short of breath a lot

That last one belongs on the list for a reason we come back to below.

Notice what the list is doing. It replaces a number you cannot know with things you already know about your own month. If bleeding regularly interferes with your sleep, your work, your exercise or your ability to leave the house, that is the criterion clinicians now care about, and it is worth an appointment.

You are not unusual

A survey of European women found heavy menstrual bleeding in 27%, and some studies put the figure above 50% globally (StatPearls).

Those numbers are far apart because studies define heavy bleeding differently, some by measured blood loss and some by its effect on daily life, which is the same problem you have in the bathroom. What they settle is that this is common, and that raising it with a doctor is ordinary rather than dramatic.

What is usually behind it

Before anything else, a doctor will want to know whether you could be pregnant. Bleeding in early pregnancy, including miscarriage and ectopic pregnancy, sits outside the classification below and is checked first (NHS).

For bleeding from the uterus itself, clinicians use the FIGO system, known as PALM-COEIN (Int J Gynecol Obstet, 2023):

Group	What it covers
PALM, structural	Polyps, adenomyosis, leiomyoma (fibroids), malignancy or hyperplasia
COEIN, non-structural	Coagulopathy (a bleeding disorder), ovulatory dysfunction, endometrial causes, iatrogenic (a medicine or device), and not otherwise classified

Two things about that system matter more than the letters. Heavy bleeding is a symptom rather than a diagnosis in itself. And more than one letter can apply to the same woman at the same time: fibroids and an ovulatory problem together, for instance, which is why one finding on a scan does not close the question.

The NHS names the same territory in plainer words: fibroids, endometriosis, adenomyosis, pelvic inflammatory disease and PCOS, conditions that make you bleed more easily such as von Willebrand disease, medicines including anticoagulants, and, rarely, womb cancer (NHS).

Two of these are worth pulling out because women often do not connect them. A bleeding disorder can go unnoticed for years when heavy periods are its main sign, so it is worth telling your doctor about nosebleeds, bruising easily, or bleeding heavily after dental work, surgery or childbirth, in yourself or in your family. And perimenopause changes cycles before it ends them, so heavier, closer-together periods in your forties are a recognized pattern. That does not make new or noticeably worse bleeding after 40 something to wait out, because age also changes what needs checking. Our guide to perimenopause covers how the stages are told apart.

The iron connection, and why this page exists

Here is the loop that catches a lot of women. Blood carries iron. Losing more blood every month drains iron stores faster than food replaces them. Stores fall for months or years before anemia shows up on a standard blood count, because anemia is a late sign of iron deficiency rather than an early one (Clinical Medicine, 2021).

So a woman can have heavy periods, be genuinely short of iron, feel exhausted, and be told her blood count is normal. All of those can be true at once.

The test that sees it earlier is ferritin, which measures stores rather than the red cells you have left. FIGO puts assessment of iron status among the things common to everyone with heavy menstrual bleeding (Int J Gynecol Obstet, 2023), so this is a reasonable thing to ask for rather than an unusual request. Ferritin also rises with inflammation, infection and liver problems, which is why it is read alongside the rest of your results rather than on its own.

Heavy bleeding makes iron deficiency an important possibility when you are tired, breathless, getting headaches or finding exercise harder than it used to be. It is not the only explanation: thyroid problems, poor sleep, low mood, pregnancy, infection and medicines produce the same tiredness. That is an argument for testing rather than for assuming, in either direction. Our guides to iron deficiency and fatigue cover what to do with the answer, and iron is one of several possible contributors to hair shedding.

What your doctor will do

Expect a conversation about your cycle first: how often, how long, how much it interferes. A pregnancy test comes early if there is any chance you are pregnant. The NHS says a GP will usually arrange blood tests to look for underlying conditions such as iron deficiency anemia (NHS). Depending on what the history and examination suggest, imaging or a sample of the womb lining may follow (StatPearls). Scans are not automatic for everyone.

Two things make that appointment more useful. Track two or three cycles before you go, with the specifics from the list above rather than the word "heavy". And say plainly what you want fixed: the bleeding itself, the tiredness, the pain, or the not knowing. They lead to different next steps.

Start the diary before the appointment, not instead of it. If the bleeding is severe, if you have symptoms of anemia, if you could be pregnant, or if you are bleeding between periods, book now and track afterwards.

What can be done

The NHS lists contraception such as the intrauterine system or the combined pill, tranexamic acid to reduce the bleeding, and prescription-only anti-inflammatory painkillers such as mefenamic acid or naproxen, which can ease pain and blood loss together. Specialist options include endometrial ablation, removal of fibroids, and hysterectomy (NHS).

Which one fits depends on the cause, on whether you want to be pregnant in future, on what else you take, and on what you find tolerable. That is a discussion to have with a doctor, and having it beats waiting for perimenopause to end the problem for you.

If the tiredness has become the main problem, ask about ferritin alongside the full blood count. The difference between those two tests is often the difference between an answer and another year of being told nothing is wrong.

Frequently asked questions

How do I know if my periods are heavy?

You do not need to measure anything. The NHS signs are practical: changing a pad or tampon every one to two hours, needing two types of period product at once, periods lasting more than seven days, passing clots larger than about 2.5 cm, bleeding through to clothes or bedding, avoiding things you would otherwise do, or feeling tired and short of breath a lot. One or more of these is a reason to raise it with a doctor.

When is heavy bleeding an emergency?

If you could be pregnant and you have heavy bleeding, severe tummy pain, pain in your shoulder, or you feel sick, faint or dizzy, the NHS says to call 999, because these can be signs of an ectopic pregnancy or another problem needing immediate treatment. Any bleeding after your periods have stopped for good needs a GP appointment, and you should not have to wait more than two weeks to see a specialist.

How common are heavy periods?

Common enough that raising it is ordinary. A survey of European women found heavy menstrual bleeding in 27 percent, and some studies put it above 50 percent globally. Estimates vary widely because studies define heavy bleeding differently, from measured blood loss to its effect on daily life.

Can heavy periods cause iron deficiency?

Yes, and it is one of the most common reasons women become iron deficient. Blood loss removes iron month after month, and stores fall long before anemia appears on a standard blood count. FIGO recommends that iron status be assessed in everyone with heavy menstrual bleeding, which is why ferritin is worth asking about.

Does being tired mean I am iron deficient?

Not on its own. Heavy bleeding makes iron deficiency an important possibility when you are tired, breathless, getting headaches or finding exercise harder than it was. But thyroid problems, poor sleep, depression, pregnancy, infection and medicines all cause the same tiredness, which is why the answer comes from a blood test rather than from reasoning.

What treatments exist for heavy periods?

More than most women expect. The NHS lists contraception such as the intrauterine system or the combined pill, tranexamic acid to reduce bleeding, and prescription anti-inflammatory painkillers such as mefenamic acid or naproxen. Specialist options include endometrial ablation, fibroid removal and hysterectomy. Which fits depends on the cause and on whether you want to be pregnant in future.

References

1. Heavy periods · NHS
2. Vaginal bleeding in pregnancy · NHS
3. Postmenopausal bleeding · NHS
4. Abnormal uterine bleeding · StatPearls, NCBI Bookshelf
5. Contemporary evaluation of women and girls with abnormal uterine bleeding: FIGO Systems 1 and 2 · International Journal of Gynecology & Obstetrics, 2023
6. Iron deficiency anaemia: a guide for the general physician · Clinical Medicine, 2021