What causes you to pass old dark blood during period instead of the normal bright red?

Question

What causes you to pass old dark blood during period instead of the normal bright red?

Answer 1

i looked online, and black or brown blood is completely  normal. Its the color of the clotted blood or lining. If you have a lot of it, u need to drink a lot more water and hot beverages. If the clots are like bigger than a tennis ball, u need to see a gynecologist (not to scare u, but) becuase it could be serious.

Answer 2

This happened to me. It depends on what you are eating and what vitamins. It lightened up, so nothing is wrong I garuntee