The amount of blood you lose during menstruation is something you should know, as an abnormal amount of discharge can be a sign that there are problems with your health. 

Normal menstruation lasts for 3-7 days, it is characterized by regularity, as well as the absence of severe pain and fatigue. Blood loss, in this case, is up to 250 ml per cycle and can reach 40-50 ml, or 2-3 tablespoons, per day, even if it may seem much more than that. This is explained quite simply: menstrual discharge doesn’t consist of blood only. 

Light

Light bleeding generally means the loss of 5 to 12 g of blood per day and requires hygiene products marked as light (or size 1 and 2). 

It means you should change a pad or a tampon up to 1-2 times a day.  

Medium 

Blood discharge is considered to be ‘medium’ when you need to replace your hygiene product every 4 hours. Medium flow women mostly use products marked “Normal” (size 3). As a rule, blood loss is 12-15 g. 

Heavy  

Heavy menstrual discharge usually requires hygiene products marked "super" (size 4). They need to be changed every 3-4 hours. Blood loss, in this case, is 15-18 g. 

If you have recently noticed that you need to change your pads or tampons of increased absorption capacity every 1-2 hours, your bleeding is abnormally high. You require urgent medical attention.

Remember that the flow is heavier during the first two days of menstruation, after which it gradually decreases in intensity. However, when calculating the volume of blood loss, only the total amount of the whole period is relevant, not, say, for a certain day.