Some women lose an excessive amount of blood during their period.
The medical term for heavy periods is "menorrhagia". It can sometimes happen along with other symptoms, such as period pain.
Heavy bleeding doesn't necessarily mean there's anything seriously wrong, but it can affect a woman physically and emotionally, and disrupt everyday life.
See your GP if you're worried about heavy bleeding during or between your periods.
This page covers:
How much is heavy bleeding?
Bleeding after childbirth
How much is heavy bleeding?
It's difficult to define exactly what a heavy period is because this varies from woman to woman. What's heavy for one woman may be normal for another.
The average amount of blood lost during a period is 30 to 40 millilitres (ml), with 9 out of 10 women losing less than 80ml. Heavy menstrual bleeding is considered to be 60ml or more in each cycle.
But it's not usually necessary to measure blood loss. Most women have a good idea of how much bleeding is normal for them during their period, and can tell when this amount increases or decreases.
A good indication that your blood loss is excessive is if:
- you feel you're using an unusually high number of tampons or pads
- you experience flooding (heavy bleeding) through to your clothes or bedding
- you need to use tampons and towels together
What causes heavy periods?
In some cases, the cause of heavy periods can't be identified. But there are a number of conditions and some treatments that can cause heavy menstrual bleeding.
Conditions that can cause heavy bleeding include:
- polycystic ovary syndrome (PCOS) – a common condition that affects how the ovaries work; it causes irregular periods, and periods can be heavy when they start again
- pelvic inflammatory disease (PID) – an infection in the upper genital tract (the womb, fallopian tubes or ovaries) that can cause pelvic or abdominal pain and bleeding after sex or between periods
- fibroids – non-cancerous growths that develop in or around the womb and can cause heavy or painful periods
- adenomyosis – when tissue from the womb lining becomes embedded in the wall of the womb
- endometriosis – when small pieces of the womb lining are found outside the womb, such as in the fallopian tubes, ovaries, bladder or vagina (although this is more likely to cause painful periods)
- an underactive thyroid gland (hypothyroidism) – where the thyroid gland doesn't produce enough hormones, causing tiredness, weight gain and feelings of depression
- cervical or endometrial polyps – non-cancerous growths in the lining of the womb or cervix (neck of the womb)
- blood clotting disorders, such as Von Willebrand disease
- cancer of the womb (although this is relatively rare)
Medical treatments that can sometimes cause heavy periods include:
Diagnosing heavy periods
Your GP will usually investigate heavy periods by carrying out a pelvic examination.
A blood test may also sometimes be recommended to check for iron deficiency (anaemia).
If an underlying cause of your heavy periods isn't found, you may have an ultrasound scan.
Read more about diagnosing heavy periods.
Treating heavy periods
You may not need treatment if a serious cause isn't suspected, or the bleeding doesn't affect your everyday life.
If treatment is necessary, medication is usually tried first. But it may take a while to find a medication that's effective and suitable for you.
Some treatments also act as contraception.
If medication doesn't work, surgery may be a possible treatment option.
Read more about treating heavy periods.
Bleeding after childbirth
After having a baby, heavy vaginal bleeding, known as lochia, is very common and completely normal. It's your body's way of getting rid of the womb lining after you've given birth.
The bleeding can last from two to six weeks, and the blood may come out quickly, or slowly and evenly.
The amount of blood loss varies between women. If you've had a caesarean section, you'll also have some bleeding as the womb lining sheds, although it may be lighter than if you'd had a vaginal birth.
You'll need to use thick sanitary pads to start with while the bleeding is at its heaviest.
Once the flow settles down, you can switch to using normal sanitary pads. Always wash your hands before and after changing your pad.
Don't use tampons for the first six weeks after the birth as it increases the risk of your womb becoming infected.
The colour of the blood will also change in the days and weeks after childbirth. It'll be bright red for the first few days and may contain small clots.
As the bleeding becomes less heavy, the colour of the blood will lighten, becoming pinkish and more watery.
It's important to make sure you get plenty of rest and don't overdo it during this time.
You should seek medical advice from your GP or midwife if:
- the bleeding smells unpleasant
- you get a fever or chills
- you still have heavy, bright red bleeding after the first week
- you have lower tummy pain on one or both sides
Dial 999 to ask for an ambulance if you experience very heavy bleeding (bleeding that soaks through more than one pad an hour) after having a baby.
It could be a postpartum haemorrhage caused by a piece of placenta still inside your womb. You may need antibiotics or an operation to remove the piece of placenta.