The average person loses about 50 milliliters of blood per period, which is roughly 3 tablespoons. Most people fall somewhere between 25 and 70 milliliters per cycle, though the full range spans much wider. Anything over 80 milliliters per cycle is considered heavy menstrual bleeding.
That number is smaller than most people expect, partly because menstrual fluid isn’t pure blood. Only about 36% of what you see is actually blood. The rest is a mix of uterine lining tissue, mucus, and clots. So while it can look like a lot, the actual blood volume is relatively modest for most people.
What “Normal” Actually Looks Like
A study of 100 women with regular cycles found blood loss ranging from as little as 7 milliliters to as much as 179 milliliters. Half of participants fell between 23 and 68 milliliters. That’s a wide spread, which is why comparing your period to someone else’s isn’t particularly useful. What matters more is whether your flow is consistent from cycle to cycle and whether it’s causing symptoms like fatigue or dizziness.
Most periods last between 3 and 7 days. Flow is typically heaviest during the first two days, then tapers off. A period lasting longer than 7 days, or one that stays heavy throughout, moves into territory worth paying attention to.
How to Estimate Your Flow
Since no one is measuring their menstrual blood in a lab, the easiest way to estimate is by tracking how many products you use and how full they are. Tampon absorbency ratings give you a rough guide:
- Light tampon: holds about 3 milliliters
- Regular tampon: holds about 5 milliliters
- Super tampon: holds about 12 milliliters
If you use menstrual cups or discs, most have measurement lines printed on them, which makes tracking even easier. Pads are harder to measure precisely, but a fully soaked regular pad holds roughly 5 to 15 milliliters depending on the brand.
Clinicians sometimes use a visual scoring system called the Pictorial Blood Loss Assessment Chart (PBAC) to help people estimate their flow more precisely. It assigns points based on how saturated each product is: a lightly stained pad scores 1 point, a moderately soiled pad scores 5, and a completely soaked pad scores 20. Tampons use a similar scale, with a fully saturated tampon scoring 10. Small clots score 1, large clots score 5. A total score above 100 for a single cycle suggests heavy bleeding. You can use this framework informally just by noticing whether you’re regularly soaking through products or passing large clots.
When Bleeding Counts as Heavy
Heavy menstrual bleeding, clinically called menorrhagia, is defined as losing more than 80 milliliters of blood per cycle. In practical terms, that looks like soaking through a regular tampon or pad every hour for several consecutive hours, needing to change products overnight, passing clots larger than a quarter, or bleeding for more than 7 days.
Heavy periods are common. Roughly one in three people who menstruate will seek help for heavy bleeding at some point. The causes range from hormonal imbalances and fibroids to thyroid problems and bleeding disorders. If you’ve had heavy periods since your very first cycle, and you also bruise easily, get nosebleeds often, or have had unusual bleeding after dental work or surgery, that pattern can point toward an underlying clotting issue like von Willebrand disease, which is worth investigating.
How Heavy Periods Affect Your Body
The biggest concern with consistently heavy periods is iron deficiency anemia. Every milliliter of blood contains iron, and when you lose more than your body can replace through diet alone, your iron stores gradually drop. This doesn’t happen overnight. It builds over months or years, which is why many people adapt to feeling tired without realizing it’s connected to their period.
Symptoms of iron deficiency anemia include extreme tiredness, weakness, pale skin, shortness of breath, dizziness, cold hands and feet, brittle nails, and restless legs. Some people develop unusual cravings for ice, dirt, or other non-food items, a condition called pica. If any of these sound familiar and you also have heavy periods, the connection is worth exploring with a blood test.
What Changes Your Flow
Your period volume isn’t fixed. Several factors can shift it from cycle to cycle or change it over the course of your life.
Hormonal contraceptives are one of the biggest influences. IUDs that release hormones typically lighten periods significantly, and some people stop bleeding altogether. Birth control pills often reduce flow as well. On the other hand, copper IUDs can make periods heavier, especially in the first several months after insertion.
Age plays a role too. Periods in the first few years after menarche and the years leading up to menopause tend to be more unpredictable in both timing and volume. During perimenopause, hormonal fluctuations can cause some cycles to be unusually heavy.
Stress, significant weight changes, intense exercise, and certain medications (particularly blood thinners) can also affect how much you bleed. If your flow changes noticeably and stays different for more than two or three cycles, that shift is worth noting, especially if it’s accompanied by pain, fatigue, or other new symptoms.