Hi there.
Blood color is red if it still carries the oxygen that it is supposed to deliver to the tissues. Blood will
turn dark red or even black if this is already low or devoid of oxygen.
Menstrual blood is a mixture of both oxygenated and deoxygenated blood, and it is indeed possible to have
deoxygenated blood seen as black blood during menses. This black blood may also be blood that has been in the
cervix or vaginal tract for at least 48 hours, loosing all its oxygen content, and even undergo some degree of
coagulation (appearing as globs).
If you have other symptoms such as vaginal pain, fever, different smell of the discharge, or when menses is
unusually long or heavy, then you may have to see your gynecologist.
Regards.
