Heavy Periods With Blood Clots: What Is Normal and When to Get Checked
Small blood clots during a period are common. Clots about 2.5 cm (1 inch) across or larger, soaking a pad or tampon every two hours or less, or bleeding for more than seven days point to heavy menstrual bleeding, which doctors define as losing more than 80 ml of blood in a cycle. It is treatable, and the cause can usually be found with a history, a blood test and a pelvic ultrasound.
Book a gynaecology appointment if this describes your periods. Get urgent care if you soak through protection every hour, feel faint, or bleed at all after menopause.
Are blood clots during periods normal?
Yes, small clots are normal. Menstrual blood is meant to stay liquid on its way out. The uterus releases natural anticoagulants alongside the blood, and these break down clots before they leave the body. When the flow is brisk, blood can leave faster than those agents can work, and the blood clots. That is why clots tend to appear on your heaviest days.
Dr Santoro explains that women who pass many clots are likely bleeding more than average. They may be at risk of anaemia, or they may have a structural problem in the uterus. She also advises getting checked if you change a pad or tampon every two hours for more than a day.
So a clot is rarely the problem by itself. Clots in the menstrual flow are not the same as clots in a vein, and on their own they are not dangerous. They are a clue about how heavy your bleeding is, and heavy bleeding is the thing worth investigating.
What counts as a heavy period?
Doctors call it heavy menstrual bleeding (the older term is menorrhagia) when you lose more than 80 ml of blood in a cycle, or your period lasts longer than seven days. Nobody measures millilitres at home, so clinicians go by what you notice day to day.
What you notice
What it suggests
Soaking a pad or tampon every 2 hours or less, for several hours
Flow is heavier than the usual range
Needing double protection, such as a pad plus a tampon
Flow is heavier than the usual range
Waking at night to change protection
Heavy flow, often with flooding
Clots about 2.5 cm (a US quarter) or larger
A recognised marker of heavy bleeding
Periods lasting longer than 7 days
Meets the definition by duration alone
Tiredness, dizziness, breathlessness
Possible iron deficiency anaemia
Bleeding between periods, or a sudden change in your usual pattern
Needs a cause looked for
Interactive · Symptom checker
Check your pattern
Tick everything that applies to your recent periods. This is a guide for deciding how soon to be seen, and it does not diagnose anything.
Get urgent care
Soaking through a pad or tampon every hour for 2 hours or more
Feeling faint, very dizzy, breathless or with a racing heartbeat
Heavy bleeding with fever or severe pain
Heavy bleeding while pregnant or possibly pregnant
Any bleeding after menopause
Book a gynaecology appointment
Changing protection every 2 hours or less, for several hours
Passing clots about 2.5 cm or larger
Periods lasting longer than 7 days
Using double protection or waking at night to change
Constant tiredness or breathlessness on stairs
Bleeding between periods, or a sudden change in your pattern
Periods that get in the way of work, school or sleep
Nothing ticked yet
Choose the statements that match your periods and your result appears here.
How big is too big? A blood clot size guide
Gynaecologists often use coins to describe clot size, because patients find it easier than centimetres. The usual dividing line is a US quarter, which measures about 2.5 cm. Smaller clots mostly turn up on the heaviest day. Quarter-sized or larger clots, especially ones that come back every cycle, signal heavier bleeding that is worth investigating.
What causes heavy bleeding during periods?
Gynaecologists sort the causes of abnormal uterine bleeding with the FIGO PALM-COEIN system, which the American College of Obstetricians and Gynecologists has adopted. PALM covers structural causes you can see on imaging or in tissue. COEIN covers causes that are not structural. More than one can be present at the same time.
The mix varies by age and by hospital. In a 2023 study of 336 women with abnormal uterine bleeding, fibroids were the most frequent finding (37.5%), followed by ovulation disorders (24.1%) and adenomyosis (20.8%). Because causes overlap, those percentages add up to more than 100.
Structural causes
Fibroids. Benign muscle growths in the uterus. Those that grow into the uterine cavity are the most likely to cause heavy periods with large clots.
Polyps. Small growths on the lining that can cause heavy or irregular bleeding.
Adenomyosis. The womb lining grows into the muscle wall, producing a bulky, tender uterus and heavy, painful periods.
Hyperplasia and, rarely, cancer. Thickened or abnormal lining cells need to be ruled out, particularly after 40 or with bleeding between periods.
Hormonal and ovulation causes
When ovulation is irregular, the lining can build up and then shed heavily. Perimenopause, polycystic ovary syndrome (PCOS), puberty and an underactive thyroid are the usual reasons.
Clotting disorders
Von Willebrand disease, an inherited shortage or fault in a clotting protein, is an under-recognised cause of heavy periods that have been heavy since the first one. Low platelets or other clotting protein problems can do the same.
Medicines, devices and other factors
Blood thinners and copper IUDs can increase flow. Pregnancy-related bleeding, including miscarriage, can also look like a heavy period with clots, so take a pregnancy test if your period is late and unusually heavy.
Heavy periods with blood clots after 40
Heavy bleeding and larger clots become more common in the forties. As perimenopause begins, ovulation turns irregular and the lining can thicken before it sheds. The result is a period that is later, longer and heavier than you are used to.
Perimenopause is a common explanation, but it should not be assumed. Fibroids, polyps and lining changes are also more frequent at this age, and they need to be ruled out. Bleeding between periods, bleeding after sex and any bleeding after menopause should always be checked.
What to expect at the gynaecologist
Expect questions about how long your periods last, how often you change protection, how large your clots are, and whether anyone in your family has a bleeding disorder. Your doctor will ask about medicines, contraception, pregnancy and any pelvic pain.
Tests usually include a blood test, such as a complete blood count to look for anaemia, sometimes with thyroid or clotting tests, and a pelvic ultrasound to look for fibroids, polyps or adenomyosis. Some women need a sample of the lining.
Questions worth asking
What is most likely causing my heavy bleeding?
Do I need tests for anaemia, thyroid problems or a clotting disorder?
Which treatments suit my age, and do they affect future pregnancy plans?
How long before I notice a difference, and what should I do if nothing changes?
Which symptoms should send me back sooner?
How to stop heavy periods with clots: what doctors can offer
No safe treatment stops a heavy period instantly, and any article that promises one deserves caution. What doctors can do is find the cause and reduce your flow over the next cycles. The right option depends on the cause, how heavy the bleeding is, your age and whether you want to become pregnant.
Anti-inflammatory medicines such as mefenamic acid or naproxen, taken during the period, can reduce flow and ease cramps.
Tranexamic acid is a non-hormonal tablet taken on heavy days. It helps blood clots hold together, so less blood is lost. It is not suitable for anyone with a history of deep vein thrombosis, pulmonary embolism or stroke, so it should only be used on a doctor's advice.
A hormonal IUD is one of the most effective long-term options and often makes periods much lighter.
Hormonal pills or injections can regulate the cycle and thin the lining.
Iron supplements treat the anaemia that heavy bleeding can cause.
Procedures and surgery include removing polyps or fibroids, blocking the blood supply to fibroids, and endometrial ablation. Hysterectomy is considered when other options have not worked or are unsuitable.
Home remedies and diet changes are not a substitute for finding out why you are bleeding heavily. Do not start tranexamic acid or hormones on your own.
When heavy bleeding is an emergency
Go to emergency care now if you have:
Bleeding that soaks a pad or tampon every hour for two hours or more
Dizziness, fainting, breathlessness or a racing heartbeat
Heavy bleeding with fever or severe pelvic pain
Heavy bleeding while pregnant or after a possible miscarriage
Any bleeding after menopause (urgent review, not necessarily an emergency room)
Frequently asked questions
Are blood clots during periods normal?
Small clots are common, especially on the heaviest days, because blood can leave the uterus faster than its natural anticoagulants can break it down. Clots about 2.5 cm (1 inch) or larger, or clots that appear every cycle, are a sign of heavy menstrual bleeding and are worth discussing with a gynaecologist.
How much bleeding counts as a heavy period?
Heavy menstrual bleeding is usually defined as losing more than 80 ml of blood in a cycle or having periods that last longer than seven days. In daily life it often shows up as soaking through a pad or tampon every two hours or less, needing double protection, or waking at night to change.
What causes heavy bleeding during periods with clots?
Common causes include fibroids, polyps, adenomyosis, ovulation problems such as perimenopause or PCOS, thyroid disorders, bleeding disorders such as von Willebrand disease, and some medicines or copper IUDs. A doctor sorts the cause with a history, blood tests and usually an ultrasound.
Can heavy periods with clots cause anaemia?
Yes. Ongoing heavy bleeding can lead to iron deficiency anaemia, which causes tiredness, dizziness and shortness of breath. A simple blood test can check your haemoglobin and iron levels.
How can heavy periods with clots be treated?
Treatment depends on the cause. Options include anti-inflammatory medicines, tranexamic acid on heavy days, a hormonal IUD, hormonal pills or injections, iron supplements for anaemia, and procedures or surgery for fibroids, polyps or other structural problems. No safe treatment stops a heavy period instantly.
When are heavy periods with blood clots an emergency?
Seek urgent care if you soak through a pad or tampon every hour for two hours or more, feel faint, dizzy or breathless, have heavy bleeding with fever or severe pain, bleed heavily while pregnant, or bleed at all after menopause.
