What to do if I have blood in stool?

Agree wi Dr Kaplan. Possible causes of blood in stool include: fissures, fistulas, hemorrhoids, cancer, ulcers, infections, inflammation, Diverticular disease & Angiodysplasia . Get evaluated if more than a one time occurrence.
Don't ignore it!!! If it persists or has been prsent for a while and especially if there is no anal pain, you nee to see your doctor or a colorectal/gi doctor as soon as possible.