Blood clots in your period: when are they normal?

Short answer: small clots, especially on your heaviest days, are normal. Blood clots when it leaves your womb faster than your body can keep it liquid. See your GP if you regularly have clots bigger than 2.5 centimetres (about the size of a 10p coin), if you soak a pad or tampon every hour or two, or if your period lasts longer than 7 days.

Why do you get clots?

During your period your body makes substances that keep the blood liquid. When you bleed a lot and fast, that does not fully work and the blood forms small clumps. That is why clots usually appear on the first, heaviest days, or when you get up after lying or sitting for a while.

When is it too much?

Clots are often a sign of heavy periods. That is the case when:

• you often see clots bigger than 2.5 centimetres;
• you need to change a pad, tampon or cup every hour or two;
• you have to get up at night to change, or need double protection;
• your period lasts longer than 7 days;
• you feel tired, dizzy or short of breath.

Feeling tired and dizzy can point to anaemia from low iron. Read heavy periods and low iron.

Possible causes of heavy periods

• Your hormones, for example in the first years after your first period or in perimenopause.
• Fibroids or polyps in the womb.
• Adenomyosis or endometriosis.
• A copper coil.
• Sometimes a clotting disorder or medicines that thin the blood.

Your GP can find out what is going on and what helps. There are good treatments, with and without hormones.

When to get help straight away

Call your GP or 111 straight away for very heavy bleeding with fainting or dizziness, or if you are or could be pregnant and lose blood with clots.

Tracking helps your GP

Track for a few cycles how heavily you bleed, how often you change and how long your period lasts. In PERIOD. you log how heavy you bleed per day, so the conversation with your GP is concrete.

Sources: NHS, Heavy periods; NICE NG88; Thuisarts.nl (NHG), Hevige menstruatie. This article is general information, not medical advice.

Frequently asked questions

Are blood clots in your period dangerous?

Small clots are usually not dangerous. Large clots or very heavy bleeding are worth discussing with your GP.

How big can a period clot be?

Smaller than about 2.5 centimetres is usually normal. Seeing bigger clots more often points to heavy periods.

Are clots a sign of miscarriage?

Not in a normal period. If you are or could be pregnant and lose blood with clots, contact your GP or midwife.

Want to keep a clear record of your periods? Download PERIOD. on the App Store or Google Play.