35 mls (2.4 tablespoons) is the average volume of menstrual fluid lost during a cycle. However anywhere from 25–80 milliliters (1–6 tablespoons of menstrual fluid) is considered normal. Only 10% of women lose more or less than this when menstruating. The actual amount lost tends to vary from cycle to cycle for each woman.
As a guide, a regular tampon fully soaked will hold about 5-9ml of fluid, therefore the average period would soak through about 5 or 6 regular tampons (however anywhere from 4 to 11 fully soaked regular tampons is normal). A small menstrual cup (e.g. the small Yuuki cup) holds about 13ml up to the safety line, therefore three full cup-loads of menstrual fluid would be the average for a cycle (although anywhere from 2-6 full cup-loads is normal). A large menstrual cup contains about 20-25mls (therefore anywhere between 1-4 full cup-loads is normal for a large menstrual cup). A regular sanitary pad appears to range in capacity quite a bit. It’s difficult to find out information on the average capacity of a disposable sanitary pad, however it appears to be somewhere around 5-20ml.
Women 50 and older tend to have the highest average fluid loss and women 15 and under tend to have the lowest average fluid loss levels. However for women between the ages of 15-50 there is no statistically significant age difference in average menstrual fluid loss.
Excessive menstrual bleeding?
A menstrual fluid loss of greater than 80 ml or lasting longer than 7 days constitutes menorrhagia (also called hypermenorrhea).
The possible causes of this are varied. Periods soon after the onset of menstruation in girls (the menarche) and just before menopause may in some women be particularly heavy.
Alternatively, heavier than usual blood loss may be caused by an early spontaneous miscarriage (rather than a heavy period). The lining of the uterus builds up naturally under the hormonal effects of pregnancy, and an early spontaneous miscarriage may be mistaken for a heavier than normal period.
For women with regular heavy periods, over time the blood loss may prove to be greater than the body iron reserves or the rate of blood replenishment. This leads to anemia (which is what my mother suffered from right up until menopause). Symptoms attributable to anemia include shortness of breath, tiredness, weakness, tingling and numbness in fingers and toes, headaches, depression, becoming cold more easily, and poor concentration. Anemia can be treated by taking iron tablets to help restore normal hemoglobin levels.