What does brown blood before periods mean?

Brown is Blood: Brown is blood. It is old and fully deoxygenated blood. But, blood it is.

Usually not serious: Most of the time it is simply the beginning of a period as the hormone level changes from estrogen to progesterone. However, it could be a small polyp or cervical erosion. If it continues, see your health provider.

Old blood: Brown blood may be old unoxygenated blood and is of no consequence.