Period blood clots: When they are normal and when to be concerned

• Period blood clots the size of raisins are normal and common during a heavy flow.
• But clotting may be a cause for concern if the clots are larger than a quarter or accompanied by heavy bleeding that forces you to change your pad or tampon more than once an hour.
• Abnormal clotting can be a sign of fibroids, endometriosis, adenomyosis, or a miscarriage.

People who menstruate have a lot to deal with when they're on their periods, from cramps to worrying about leaking through pads and tampons.

Another concern can be period blood clots. These clots are made up of coagulated blood and tissue which are expelled from the uterus during menstruation. They are relatively common if you have heavy periods.

Here's what you need to know about period blood clots, and when you should see a doctor about them.

Period blood clots can be normal

Period blood clots aren't always a cause for alarm. In fact, it's quite normal to experience period blood clots, says Sherry Ross, MD, OB/GYN and Women's Health Expert at Providence Saint John's Health Center in Santa Monica, California.

"Small clots the size of raisins are usually nothing to worry about and can happen during a heavy blood flow," says Ross.

These blood clots are caused by coagulation proteins that cause the blood to clot. This results in coagulated blood and tissue that are expelled by the uterus, Ross says.

Most of the time, this is considered normal clotting, as long as the clots aren't persistent. Ross says these clots typically occur when you have a heavy flow and the blood leaves the uterus slowly.

However, in other cases, clots may be caused by a medical condition.

Clotting may be caused by an underlying condition

There are instances where heavy periods and clotting may not be normal and be caused by an underlying condition. Ross says to look out for signs like:

• Blood clots larger than a quarter
• Persistent clotting
• Heavy clotting or bleeding that forces you to change your pad or tampon more than once an hour
• Weakness and dizziness that may be caused by anemia (low blood counts) which may be a result of the heavy bleeding

Some conditions that may lead to abnormal clotting and bleeding are:

Fibroids

Fibroids are non-cancerous growths in and around the uterus. Ross says uterine fibroids are the most common benign pelvic tumor in women. Sometimes, fibroids cause no symptoms. If they do cause symptoms, Ross says you may experience irregular heavy bleeding, cramping, and pelvic pain and pressure. Anywhere between 20% and 70% of women will experience fibroids during their reproductive years.

Endometriosis

Endometriosis is a condition where tissue that normally lines the uterus is found outside the uterus. Ross says that these "endometrial implants" can be found on the ovaries, fallopian tubes, bowels, bladder, or anywhere else in the pelvis. Symptoms range from mild to severe and may include painful periods, painful sex, lower back pain, pelvic pain, and infertility. About 1 in 10 women have endometriosis.

Adenomyosis

Adenomyosis is a condition where the tissue and glands that line the uterus grow into the uterus's muscular wall. Ross says the tissue responds by thickening, breaking down, and bleeding during each menstrual cycle, which leads to disruptive symptoms. These symptoms include an enlarged uterus, painful periods, heavy, irregular bleeding, and infertility. It may affect 20% to 35% of women.

Miscarriage

A miscarriage, also known as spontaneous abortion, is when you lose a pregnancy before 20 weeks. During a miscarriage you will experience vaginal bleeding (including passing clots) and cramping. About 10% to 15% of pregnancies result in a miscarriage.

Insider's takeaway

If your clots are smaller than a quarter and not persistent, they are most likely normal. However, if they are bigger than a quarter and accompanied by other symptoms, like irregular and extra heavy periods, you should speak to your OB-GYN to figure out what's going on and get you feeling better.

Related articles from Health Reference:

• 9 reasons why your period may be late, including stress, changes to sleep schedule, and more
• Why you might be cramping a week before your period - from pregnancy to a UTI
• 11 reasons why your period may be early, including stress and birth control
• The best foods to eat when you have period cramps - and which foods you should avoid
• Why is my period blood brown? How to know if it's normal and when to see a doctor