The colour and texture of period blood vary from person to person. Passing blood clots during your period can be a little alarming at first, but for the most part, it is entirely normal and not a cause for concern. When you start using a menstrual cup, you may notice these clots more than if you were using a tampon, as the blood is being collected rather than absorbed. Period blood clots usually look like bright or dark red clumps or chunks with a jelly-like consistency. You might notice them more on the heaviest days of your period (usually days 1-3).
Passing small clots is normal, however, if you are regularly passing large clots (bigger than an Australian 10 cent coin) it is best to see a doctor to investigate underlying causes.
What causes menstrual blood clots?
During the menstrual cycle, the lining in the uterus (also known as the endometrium) grows and thickens, then sheds during your period if you do not become pregnant.
When this lining sheds, it mixes with blood, blood by-products, mucus and tissue and pools at the bottom of the uterus until the cervix contracts to expel it through the vagina. While it is waiting here, the body releases anticoagulants to break the lining down so that it can pass easily through the cervix. Menstrual blood clots occur when the blood flow outpaces the body’s ability to release anticoagulants that break them down. This is why you may experience clots more frequently during the heaviest days of your period.
In some cases, larger clots can be caused by conditions such as uterine fibroids, endometriosis, adenomyosis or cancerous tumours that obstruct the uterus. Hormonal imbalances can also affect the heaviness of your period and lead to more clotting. Passing large clots and heavy bleeding can also be a sign of miscarriage, so if you experience this and suspect you could be pregnant, seek medical attention right away.
When should I be concerned?
If you are repeatedly passing large clots (larger than a 10 cent piece), experiencing pain or very heavy bleeding (enough that you need to change your menstrual cup, tampon or pad every hour), see your doctor.
Treatment for menstrual blood clots
If you are concerned about particularly heavy bleeding or frequently passing large clots, see your doctor to investigate any underlying issues. One of the main complications of heavy menstrual periods is iron deficiency anaemia, which can cause a range of symptoms such as fatigue, weakness, shortness of breath and chest pain.
Hormonal contraceptives or medications may be recommended to control heavy bleeding and period blood clots.
Surgery or other treatment may also be required to treat the conditions such as fibroids, miscarriage, endometriosis or cancerous growths that may be causing your blood clots.