On average, during a menstrual period, a person loses about 30 to 40 milliliters (2 to 3 tablespoons) of blood, though some studies suggest it can be closer to 60 milliliters (about 4 tablespoons)

. Menstrual fluid is not pure blood; it typically contains about 36-50% blood, with the rest being tissue, mucus, and other uterine lining components

. The typical total menstrual fluid volume ranges from about 20 to 90 milliliters (1 to 5 tablespoons), with blood making up roughly half of that

. Some sources consider up to 80 milliliters of blood loss per period as normal, while blood loss above 80 milliliters may be classified as heavy menstrual bleeding (menorrhagia)

. Heavy bleeding may be indicated by:

• Soaking through one or more tampons, pads, or cups per hour for several hours
• Needing to use double protection to prevent leaking
• Bleeding lasting more than seven days
• Passing large blood clots (larger than a quarter or 1 inch)
• Fatigue or signs of anemia

In summary, normal blood loss on a period is roughly 30-60 milliliters, with anything above 80 milliliters considered heavy and potentially requiring medical attention if accompanied by other symptoms