Period Blood Clots: What’s Normal & When to See a Doctor

16 min read
Period blood clots and heavy menstrual flow explained

Noticing blood clots during your period can feel a little confronting, especially the first time you see one sitting in a menstrual cup or disc.

The good news is that small blood clots can be a normal part of menstruation, particularly on heavier-flow days.

If you use a menstrual cup or menstrual disc, you may notice clots more than you did when using tampons or pads. Cups and discs collect menstrual fluid rather than absorbing it, so you get a much clearer look at the colour, texture and contents of your flow.

Period clots are often dark red, burgundy or bright red and can look thick, soft or jelly-like. They’re usually more noticeable when your flow is heavier, which for many people is towards the beginning of the period.

Occasional small clots generally aren’t a reason to worry. Regularly passing much larger clots, particularly alongside very heavy bleeding, significant pain or symptoms of iron deficiency, is worth discussing with your GP.

Key takeaways

  • Small menstrual blood clots can be a normal part of a period.
  • Clots are often more noticeable on heavier-flow days.
  • Cups and discs may make clots easier to see because they collect menstrual fluid rather than absorbing it.
  • Australian health guidance uses clots larger than a 50-cent coin as one possible sign of heavy menstrual bleeding.
  • Clot size alone doesn’t diagnose a problem. How heavily you bleed, how long your period lasts, pain and the effect on your everyday life also matter.
  • Heavy periods can lead to iron deficiency, with or without anaemia.
  • A significant change in your usual bleeding pattern is worth paying attention to.

On this page

What are period blood clots?

Your period isn’t made up of blood alone.

Menstrual fluid contains blood along with mucus, cells and tissue shed from the lining of the uterus, known as the endometrium.

As this material leaves the uterus, some of the blood can clot together before it passes through the cervix and vagina.

The result may be a soft or jelly-like clump that looks quite different from the more liquid menstrual flow around it.

Period clots can be:

  • bright red
  • dark red
  • burgundy
  • brownish-red, particularly when blood has taken longer to leave the body

The colour alone usually isn’t as important as whether there has been a significant change in the amount you’re bleeding, the size and frequency of the clots or how you feel.

For more on colour changes during menstruation, read our guide to what the colour of your period blood can mean.

Why do period blood clots happen?

During each menstrual cycle, the lining of the uterus thickens in preparation for a possible pregnancy.

If pregnancy doesn’t occur, much of that lining is shed during your period.

Your body has systems that both form clots and break them down. During menstruation, this helps blood and tissue leave the uterus without simply forming one large clot.

When bleeding is heavier, or menstrual blood collects briefly before leaving the uterus, some clots may remain intact and pass with the rest of your menstrual fluid.

This is one reason clots tend to be more noticeable on heavier-flow days.

Seeing a clot therefore doesn’t automatically mean something has gone wrong with your body's normal clotting system.

Why do cups and discs make clots more noticeable?

If you’ve recently switched from pads or tampons to a menstrual cup or disc, you might suddenly think your period has become much more clotted.

It may simply be that you can see your flow differently.

Pads and tampons absorb menstrual fluid. Once blood, mucus and endometrial tissue have soaked into an absorbent product, their original texture can be difficult to distinguish.

A menstrual cup or menstrual disc collects the fluid instead.

When you empty it, you may be able to see:

  • liquid menstrual blood
  • mucus
  • small clots
  • pieces of shed endometrial tissue
  • changes in the colour and thickness of your flow from one day to the next

So noticing clots after switching to a cup or disc doesn’t necessarily mean you have suddenly started producing more of them.

What size period clot is normal?

There isn’t a precise dividing line between a “normal” and “abnormal” menstrual clot.

Small, occasional clots can occur during an otherwise normal period, particularly when flow is heavier.

In Australian health guidance, regularly passing clots larger than a 50-cent coin is one sign that your menstrual bleeding may be heavy.

An Australian 50-cent coin is about 3 centimetres across.

That doesn’t mean a single clot slightly larger than this automatically indicates a medical condition.

It’s more useful to look at the whole picture:

  • Are you passing large clots repeatedly?
  • Has this changed from what’s normal for you?
  • Are your periods particularly heavy?
  • Are you bleeding for longer than usual?
  • Are you leaking through period products or needing very frequent changes?
  • Are you experiencing significant pelvic pain?
  • Do you feel unusually tired, dizzy, weak or short of breath?

If the answer to several of these is yes, it’s worth discussing your bleeding with a healthcare professional.

What can cause large or frequent period blood clots?

Large or frequent clots are often associated with heavier menstrual bleeding rather than being a separate condition in themselves.

Sometimes there is no identifiable underlying cause.

In other cases, heavy bleeding and clotting may be associated with:

Fibroids

Uterine fibroids are non-cancerous growths that develop from the muscle of the uterus.

Depending on their size and location, they can contribute to heavy or prolonged periods, larger blood clots, pelvic pressure and bladder or bowel symptoms.

Fibroids growing towards or into the uterine cavity are particularly likely to affect menstrual bleeding.

Adenomyosis

Adenomyosis occurs when tissue similar to the lining of the uterus is found within the muscular wall of the uterus.

It can cause heavy periods, significant period pain, pelvic pain and larger menstrual clots.

Adenomyosis is sometimes confused with endometriosis, but they are different conditions, although some people have both.

Uterine polyps

Uterine polyps, also called endometrial polyps, are growths arising from the lining inside the uterus.

They are usually benign but may cause heavy or irregular periods, spotting between periods or bleeding after sex.

If a polyp contributes to heavier menstrual flow, visible clots may also become more noticeable.

Changes in ovulation and hormones

Periods can become heavier when ovulation is irregular.

This can occur during puberty, in perimenopause and with hormonal conditions such as polycystic ovary syndrome (PCOS).

Thyroid conditions can also affect menstrual bleeding.

Bleeding disorders

Conditions that affect blood clotting, including von Willebrand disease and some platelet disorders, can cause periods to be unusually heavy or prolonged.

A bleeding disorder is particularly worth considering if you’ve had very heavy periods since they first started or you also bruise easily, have frequent nosebleeds or experience prolonged bleeding after dental treatment, surgery or injuries.

Medicines

Some medicines, including anticoagulants or blood-thinning medicines, can make periods heavier.

Endometriosis

Endometriosis is better known for symptoms such as significant period pain and pelvic pain, but some people with endometriosis also experience heavy or abnormal menstrual bleeding.

Large clots alone don’t mean you have endometriosis.

Less common causes

Abnormal bleeding can occasionally be associated with endometrial hyperplasia or cancers involving the uterus or cervix.

These are much less common explanations for menstrual clotting, particularly in younger people, but persistent abnormal bleeding still deserves assessment rather than being diagnosed from clot appearance alone.

Are blood clots a sign of a heavy period?

They can be.

Passing large clots is one of several signs used to recognise heavy menstrual bleeding.

Australian guidance also suggests your periods may be heavy if you:

  • regularly pass clots larger than a 50-cent coin
  • need to change a pad or tampon every 1 to 2 hours
  • need to change period products during the night
  • bleed through clothing or bedding
  • bleed for more than 8 days
  • have to plan work, school, exercise or social activities around your period

Heavy menstrual bleeding is increasingly defined by its impact on your physical, emotional and social wellbeing rather than by an exact number of millilitres alone.

So if your period significantly disrupts your life, that matters even if you’ve never measured how much you bleed.

Our guide to how much you bleed during your period explains heavy menstrual bleeding in more detail.

What if you use a cup or disc?

Using a higher-capacity menstrual cup or disc can make the usual advice about “changing a period product every 1 to 2 hours” harder to apply.

If you use a cup or disc, it can be more useful to notice:

  • how quickly your cup or disc fills
  • whether you’re leaking because it reaches capacity
  • approximately how much menstrual fluid you collect
  • how many times you need to empty it on your heaviest days
  • whether your usual pattern has changed

If your cup has volume markings, these can help you understand your own flow.

Just remember that menstrual fluid isn’t pure blood, so the millilitres in your cup don’t equal an exact measurement of blood loss.

When should you see a doctor about period clots?

Make an appointment with your GP if you:

  • frequently pass clots larger than a 50-cent coin
  • have consistently heavy periods
  • need to change pads or tampons every 1 to 2 hours
  • frequently bleed through clothing or bedding
  • bleed for more than 8 days
  • develop significantly heavier bleeding than is usual for you
  • experience significant or worsening pelvic pain
  • have bleeding between periods
  • have bleeding during or after sex
  • feel unusually tired, weak, dizzy or short of breath
  • find that your period is interfering with work, school, exercise, sleep or everyday activities

Heavy periods and iron deficiency

Heavy menstrual bleeding can cause iron deficiency, with or without anaemia.

Possible symptoms include:

  • persistent tiredness
  • weakness
  • dizziness
  • looking unusually pale
  • shortness of breath
  • heart palpitations

Australian clinical guidance recommends checking for iron deficiency and anaemia when someone is being assessed for heavy menstrual bleeding.

This may include blood tests such as a full blood count and ferritin level.

When is heavy bleeding urgent?

Seek urgent medical care if your bleeding becomes suddenly much heavier than usual and you feel faint, dizzy, weak or seriously unwell, or if you have severe pain.

Call triple zero (000) if you collapse, feel you may faint or are seriously unwell and can’t safely wait for medical care.

What if pregnancy is possible?

Bleeding and clots can also occur with pregnancy loss.

Very early pregnancy loss can sometimes look like an unusually heavy or late period, particularly if you didn’t know you were pregnant.

Miscarriage may cause:

  • vaginal bleeding
  • lower abdominal cramping
  • blood clots
  • passing pregnancy tissue

Bleeding during pregnancy doesn’t always mean miscarriage, but it should be assessed.

If pregnancy is possible and you develop bleeding, contact your doctor or maternity healthcare provider.

If bleeding is heavy, pain is significant or you feel unwell, seek urgent medical care.

How are heavy periods and clotting treated?

Treatment isn’t usually aimed at the clots themselves.

The goal is to reduce heavy bleeding and, where possible, address whatever is causing it.

Your doctor will take into account your symptoms, health history, the cause of your bleeding, whether contraception is wanted and whether you would like to become pregnant in the future.

Non-hormonal medicines

Options can include:

  • Tranexamic acid: a medicine taken during the period that can reduce menstrual blood loss.
  • Non-steroidal anti-inflammatory drugs (NSAIDs): medicines such as ibuprofen, naproxen or mefenamic acid can reduce period pain and may also reduce menstrual bleeding for some people.

These medicines aren’t suitable for everybody, so talk with your doctor or pharmacist before using them for heavy periods.

Hormonal treatment

Depending on your circumstances, options may include:

  • a hormonal intrauterine device (IUD)
  • the combined contraceptive pill
  • progestogen treatments
  • other hormonal contraceptive methods

A 52 mg levonorgestrel-releasing hormonal IUD is currently considered one of the most effective medical treatments for heavy menstrual bleeding when there isn’t significant underlying uterine pathology.

Iron treatment

If tests show iron deficiency, your doctor may recommend iron replacement, which may be taken orally or, in some situations, given as an iron infusion.

Treating an underlying condition

If heavy bleeding is being caused by fibroids, adenomyosis, uterine polyps or another condition, treatment may also need to address that underlying cause.

Options can range from medicines through to procedures such as hysteroscopy, removal of polyps or fibroids and, in selected circumstances, surgery.

Treatment should be based on your symptoms, preferences and future fertility plans rather than simply how dramatic a clot looks.

Should you track your period clots?

You don’t need to inspect or measure every clot.

But if you’re concerned about a change in your period, keeping a short record can be useful.

For a few cycles, note:

  • when your period starts and finishes
  • which days are heaviest
  • how often you change or empty your period products
  • whether you leak through clothing or bedding
  • whether you’re regularly seeing clots larger than a 50-cent coin
  • your level of period pain
  • tiredness, dizziness, weakness or breathlessness
  • anything that has changed from your usual pattern

You can use Period Shop’s free downloadable period tracker, your phone or whatever method you’re most likely to actually use.

If you use a cup with measurement markings, noting how full it is when you empty it can also give you useful information about your individual pattern.

Frequently asked questions

Are period blood clots normal?

Small, occasional blood clots can be a normal part of menstruation, particularly on heavier-flow days. Regularly passing large clots, having very heavy bleeding or developing a significant change from your normal period is worth discussing with your GP.

What do normal period clots look like?

Period clots are often soft or jelly-like and may be bright red, dark red, burgundy or brownish-red. Menstrual fluid also contains mucus and shed uterine lining, so its texture can vary throughout the period.

Why do I get more blood clots on heavy days?

Clots are more likely to remain visible when menstrual bleeding is heavier or blood collects briefly before leaving the uterus. Your body normally both forms and breaks down clots during menstruation, but heavier flow can make intact clots more noticeable.

Why can I suddenly see clots in my menstrual cup?

Your cup may simply be giving you a clearer look at your menstrual flow. Cups and discs collect menstrual fluid instead of absorbing it, so clots, mucus and pieces of shed uterine tissue can be much easier to see than they are on a pad or tampon.

Are clots bigger than a 50-cent coin dangerous?

Not necessarily. One large clot doesn’t automatically mean something is wrong, but regularly passing clots larger than a 50-cent coin is one recognised sign of heavy menstrual bleeding in Australian health guidance. Consider the clotting alongside the amount and duration of your bleeding, pain and how your period affects your life.

Do blood clots mean I have fibroids?

No. Fibroids can cause heavy periods and larger clots, but there are many possible reasons for heavy menstrual bleeding. Clot appearance alone can’t diagnose uterine fibroids.

Can adenomyosis cause blood clots?

Yes. Adenomyosis can cause heavy menstrual bleeding, which may make larger blood clots more likely. Clots alone don’t diagnose adenomyosis.

Can uterine polyps cause blood clots?

Uterine polyps can contribute to heavy or irregular bleeding, which may make clots more noticeable. They’re also commonly associated with bleeding between periods.

Can endometriosis cause blood clots?

Some people with endometriosis experience heavy or abnormal periods and may pass clots, but clots aren’t specific to endometriosis. Significant period pain, pelvic pain or other symptoms deserve assessment rather than trying to diagnose endometriosis from menstrual blood alone.

Can perimenopause cause heavier periods and clots?

Yes. Ovulation and hormone patterns can become less predictable during perimenopause and some people experience heavier or more irregular periods. A substantial change in bleeding should still be discussed with your GP rather than automatically assuming it’s just perimenopause.

Can I measure a heavy period with my menstrual cup?

A cup with measurement markings can help you estimate how much menstrual fluid you collect and identify patterns in your flow. But menstrual fluid contains blood, mucus and tissue, so cup measurements aren’t an exact measure of blood loss. How frequently you need to empty the cup and how the period affects you are useful information too.

Can period blood clots cause anaemia?

The clots themselves don’t cause anaemia, but frequent large clots can occur alongside heavy menstrual bleeding. Ongoing heavy blood loss can lead to iron deficiency and eventually iron deficiency anaemia.

Should I take a photo of a large period clot?

If you’re seeing unusually large clots or something that looks very different from your normal menstrual flow, a photo can sometimes help you describe what you saw to your healthcare professional. You don’t need to photograph every clot or keep checking your menstrual blood if doing so makes you anxious.

Know what’s normal for your body

Period blood isn’t always a smooth red liquid.

It can vary in colour and consistency and contain mucus, endometrial tissue and small clots. Seeing that more clearly when you start using a menstrual cup or disc can be surprising, but it doesn’t necessarily mean anything has changed.

What matters most is your overall pattern.

If you’ve always noticed a few small clots on your heavier days and otherwise feel well, they may simply be part of your normal period.

If clots suddenly become much larger or more frequent, your flow becomes significantly heavier, pain increases or your period starts interfering with your life, it’s worth getting checked.

You don’t need to wait until your period reaches a particular measurement before asking for help.

Related reading

Sources and further reading

This article provides general educational information and isn’t a substitute for individual medical advice.