Few people want to openly discuss their bodily waste products, even if -- or sometimes, especially if -- they have a compelling reason to do so. Such is the case with seeing blood in your urine or feces.
Rectal bleeding, aka hematochezia, may result in fecal blood that's bright red or a darker shade of red. It may even be black and tarry looking. Seeing fecal blood that's not bright red in color may convince you it's something other than blood, or just lead you to "keep an eye on things" or "wait it out" rather than see a doctor. However, the exact hue of the blood in your feces can reveal something about the source of the problem.
The closer a medical problem is to the anus, the redder the blood in feces will be. If the problem is further up the GI tract or colon, the fecal blood will be darker because bacteria have more time to break it down.
If fecal blood is barely visible, it may be the result of anemia, hemorrhoids or anal fissure, which is tearing of the rectal tissue. However, it could also be a sign of rectal or colon cancer, so you should get it checked out as soon as possible.
About 1 in 10 people will experience blood in the urine, aka hematuria, at some point [source: Balentine]. This condition can be caused by a number of things, from a urinary tract infection or enlargement of the prostate, to kidney stones or even cancer of the kidney, prostate or bladder. Whether or not your case of hematuria is a sign of a bigger problem is something your doctor can help you determine.