What is the cause of black or brown blood in menstrual cycles?

The normal color of menstrual blood is red, little thick and sticky. Brown or black blood can be due to slower menstrual flow and longer stay of the menstrual blood in the vaginal vault. This leads to oxidation of that blood simply because it is exposed to oxygen for more time than usual.

Stress or depression can cause menstrual flow to slow down, as it tends to make the inner lining of the uterus thin. Thinner lining leads to a delay in shedding the endometrial wall of the uterus leading to blood clots which are brown or black. The color of blood will generally be back to normal in a day or two. These clots are generally odorless and harmless.

answered by S P

That is just where the blood has clotted. It is basically the protective lining of the uterus, known as the endometrium, shedding. This lining is a protective barrier in case you become pregnant, it is released during menstration. There is nothiing to be alarmed about.

answered by C