What Causes Blood Clots on Your Period?

Menstrual Health Advice

Whether you’ve been having periods for just a few years or more like decades, passing blood clots can be unpleasant and, if you’re not used to it, alarming. If you’re worried about blood clots in your period, you should speak to a pharmacist or GP.

Blood clots in your period are usually caused by a heavy flow, which may be normal for you - in other words, they might be nothing to worry about. But sudden changes in your period can be a sign that there’s something else going on, so it’s worth getting it checked out for your own peace of mind.

What causes period blood clots?

As mentioned, heavy periods and the passing of blood clots which can be associated with them don’t always mean something’s wrong. You might have them because that’s what’s normal for you - which is why it’s important to recognise your ‘normal’ so that if anything changes unexpectedly you know to discuss any new period symptoms with a pharmacist or GP.

However, it’s worth knowing that period blood clots can sometimes be a sign of what healthcare professionals call ‘an underlying pathology’. This means that there might be another condition causing your heavy periods. That’s why you should get medical advice if you notice any changes.

Normal shedding of the uterus lining

If you’re someone who has healthy, regular periods, you might notice small clots or dark blobs passing in your period blood. While we typically refer to these as clots, that doesn’t mean that they’re made up entirely of blood. In actual fact, a period blood clot is usually made up of a mixture of blood, proteins and endometrial tissue - fragments of the lining of your womb.

Your periods are usually at their heaviest in the first couple of days of bleeding, and since period blood clots are associated with a heavy flow, that could mean you pass more of them in the early stages of your period.

You might be aware that blood clots are involved in healing wounds. As your period ends, the bleeding is stopped in the same way, through the depositing of fibrin, the gathering of platelets in your blood and the formation of a thrombus (blood clot).

After this, fibrinolysis (the breakdown of fibrin) prevents the blood clots from forming a solid mass, so they can be passed in your blood as part of your period.

Heavy periods

One of the key indicators of heavy periods is passing clots that are larger than 2.5cm or a 10p coin. If this sounds familiar, you might also recognise the following symptoms of heavy periods:

Needing to change sanitary products more often than every couple of hours
Your periods lasting longer than seven days
Feeling the need to stay home from work, school or social activities due to your periods
Frequently bleeding through onto bedding or clothes
Needing to double up on sanitary products
Feeling fatigued or short of breath.

For some people with heavy periods, they don’t have an underlying cause. But that doesn’t mean you can’t do anything about them. If you have heavy periods that have no underlying cause and your cycle is regular, then an anti-fibrinolytic medication such as Evana® Heavy Period Relief Tablets may help. These tablets contain tranexamic acid, a medicine which helps to prevent the breakdown of clots, reducing bleeding during your period.

Underlying conditions

Some people get heavy periods around the time of the menopause, when they first start having periods or after giving birth.

In some cases, however, heavy periods and the blood clots associated with them can be caused by an underlying condition.

Some examples include:

Polycystic ovary syndrome (PCOS)
Endometriosis
Fibroids
Von Willebrand disease (which affects your blood’s ability to form clots)
Anticoagulant (anti-clotting) medications.

Because of this, it’s worth speaking to a pharmacist or doctor about your heavy periods if they’ve changed recently or if they’re affecting your life. If there’s an underlying condition causing the problem, there may be other treatment options available to you.

Passing blood clots during your period isn’t necessarily a cause for concern - it can be just a normal part of your period. But if you notice any changes in the size or frequency of clots, or any other changes in your period, it’s worth speaking with a healthcare professional to rule out any other causes.

Sources

https://www.nhs.uk/conditions/heavy-periods/

https://www.nhs.uk/conditions/periods/

Hapangama, Dharani K, and Judith N Bulmer. “Pathophysiology of heavy menstrual bleeding.”
Women's health (London, England) vol. 12,1 (2016): 3-13. doi:10.2217/whe.15.81 Available at:
https://pmc.ncbi.nlm.nih.gov/articles/PMC5779569/

Yang, Heyi et al. “Proteomic analysis of menstrual blood.” Molecular & cellular proteomics :
MCP vol. 11,10 (2012): 1024-35. doi:10.1074/mcp.M112.018390 Available at:
https://pmc.ncbi.nlm.nih.gov/articles/PMC3494145/

Evana SmPC. Available at: https://www.medicines.org.uk/emc/product/15636/smpc

Davies, Joanna, and Rezan A Kadir. “Endometrial haemostasis and menstruation.” Reviews in
endocrine & metabolic disorders vol. 13,4 (2012): 289-99. doi:10.1007/s11154-012-9226-4Available at: https://pubmed.ncbi.nlm.nih.gov/23180227/

https://www.blood.co.uk/news-and-campaigns/the-donor/latest-stories/functions-of-blood-
clotting