Menstrual flow: definition and meaning
Menstrual flow is the amount of blood and tissue that leaves the body during a period. Over a whole period, a typical loss is about 30 to 40 ml (2 to 3 tablespoons), and anything over 80 ml is considered heavy. Flow usually starts heavier on days one and two and tapers off. Apps describe it as light, medium or heavy.
Light, medium or heavy
| Flow | What it often looks like |
|---|---|
| Spotting | A few drops; a liner is enough |
| Light | Regular pad or tampon lasts 4+ hours with room to spare |
| Medium | Change regular products every 3 to 4 hours |
| Heavy | Need super products, change every 1 to 2 hours, or pass clots |
Products hold different amounts: a regular tampon about 5 ml, a menstrual cup 20 to 30 ml. A full regular pad or tampon holds about one teaspoon.
What changes flow
- Thickness of the endometrium that cycle
- Hormonal birth control, which usually lightens it
- Fibroids, adenomyosis and polyps, which can make it heavier
- Perimenopause, when flow often becomes unpredictable
- Some medicines, like blood thinners
Why it matters
Tracking flow shows what's normal for you and spots changes early. Heavy flow can quietly drain iron and leave you exhausted and low, so it's worth taking seriously. See heavy menstrual bleeding and how much blood you lose on your period.
See a doctor if you soak through a pad or tampon every hour for several hours, need to double up, pass clots larger than a quarter, bleed longer than 7 days, or feel dizzy or tired. Sudden very light or absent flow with a chance of pregnancy needs a pregnancy test.
Frequently asked questions
How do I know if my flow is heavy?
If you change products every hour or two, need to double up, leak at night or pass large clots, your flow is likely heavy.
Is a light period a problem?
Usually not. Light flow is common on the pill, with stress or in perimenopause. Get checked if it's a sudden change with other symptoms.
Sources
This page is for information only and isn鈥檛 medical advice. If something worries you, please talk to a doctor.
Keep reading
How much blood do you lose on your period?How much blood do you lose on your period? Usually 20 to 90 ml, about 1 to 5 tablespoons. How to estimate yours with pads, tampons or a cup.
Heavy menstrual bleeding: definition and meaningHeavy menstrual bleeding (menorrhagia) is period bleeding that disrupts daily life. Signs your flow is heavy, common causes, and when to see a doctor.
Light period: is it normal, and why does it happen?A light period can be completely normal. Why your period might be very light or short, from contraception and stress to pregnancy, and when to see a doctor.
Menstrual clots: definition and meaningMenstrual clots are gel-like clumps of blood and lining in period flow. What they are, what size is normal, and when clots are a sign to see a doctor.
Heavy periods: what counts as heavy and what helpsHow to tell if you have heavy periods: soaking a pad every hour or two, clots, bleeding over 7 days. Causes, treatments that work, and when to get help.