I am bleeding from rectal when i use the bathroom when should i be concerned and tell my doctors?

Important: When somebody has rectal bleeding bright red rectal bleeding can be a sign of cancer hemorrhoids fissures Fistula or polyp. It can also be a sign of inflammatory bowel disease. If the blood is black it could be a sign of bleeding from the stomach or upper intestines. Should be prompt and properly evaluated by primary care doctor or gastroenterologist

Consult soon: Is the bleeding painful or painless. Painful bleeding with bowel movements can be secondary to hemorrhoids or anal fissures. Painless bleeding can be secondary to internal hemorrhoids and other conditions in the colon. There are other rarer conditions that can be concerning including colon cancer but not common at your age. Need more detailed history for best course so tell your doctor soon.