How Much Blood Do You Actually Lose During Your Period?

Have you ever wondered how much blood you lose during a typical menstrual cycle? Most people find it easy to just describe their periods as light or heavy or somewhere in between, but determining the exact amount of blood lost during a period is more complicated than you would think. This is because a lot of the fluid you lose during your period isn't actually blood. A 1985 study published in Obstetrics & Gynecology found that blood comprises only around 36% of the fluid lost during an average period. The rest is mostly uterine lining. That being said, the total amount of fluid lost does correlate with how much blood is lost.

In general, you probably lose less blood during your period than you would think. According to the CDC, the average person loses between 2 and 3 tablespoons (or around 30 to 45 milliliters) of blood during each period.

How to determine if your blood loss is normal

Menstrual blood loss is highly variable, with some people only losing around 15 milliliters and others losing at least 114 milliliters of blood each period (per American Journal of Epidemiology). However, that doesn't mean that losing a lot of blood is normal. According to Clue, blood loss is excessive if it exceeds 80 milliliters per cycle, or if it interferes with a person's quality of life.

The CDC recommends seeing a doctor if you need to change your pad or tampon more than once every two hours, or if you pass clots that are as big as (or larger than) a quarter. Left untreated, heavy bleeding can lead to anemia.

If you're curious about how much blood you personally lose during your cycle, Healthline suggests using a menstrual cup with volume markings, and logging and adding up the amount of fluid you lose throughout your period. Though it varies from person to person, your blood loss will likely be around 36% of that.