When you have blood present in your bowel movements, what does this mean?

If it's a bright red, then probably nothing serious - probably a hemmoroid. If it's dark red get to a doctor asap. Really.

Not to scare you, because even if dark red it might not be too serious... but dark red can also mean VERY serious.

Blood in your stool is always an indiction to visit your doctor. We just discussed this in class today. If it is dark and tarry then it is somewhere from the upper digestive system. If it is bright red it could be something as simple as a hemorrhoid, but could indicate something serious in the colon or lower digestive tract.