I sometimes find blood on my toilet paper after going to the toilet. what are common causes of this?

Needs investigation: Red blood in stool comes from colon, rectum or anal area .It can be due to 1 hemorroids2 polyps in colon or rectum3 inflammation and ulceration in rectum or colon4 tumors in colon, rectum or anal area, like colon or rectal cancer. I will recommend that you consult your doctor or a gastroenterologist as you may need colonoscopy to find out the cause of bleeding and treat appropriatl.