Blood in Stool — Causes and When It Is Serious
Also described as rectal bleeding, bleeding while passing motion, blood in motion.
Bright red blood on the paper is most often piles or a fissure, but blood mixed into the stool, a change in bowel habit lasting weeks, or weight loss needs colonoscopy to exclude a colorectal cause. Black, tarry stool suggests bleeding higher up and is an emergency. Iswarya Hospital, OMR Chennai, offers same-week endoscopy.
🚨 Get emergency care if you have
- •Black, tarry, foul-smelling stool — go to an emergency department
- •Heavy bleeding, dizziness or fainting
- •Blood mixed through the stool rather than on its surface
- •A change in bowel habit lasting more than three weeks
- •Unexplained weight loss or persistent tiredness with the bleeding
What causes blood in stool?
Piles (haemorrhoids)
Bright red blood on the paper or coating the stool, often painless, sometimes with itching or a lump.
Anal fissure
A sharp tear-like pain during and after passing stool, with a streak of fresh blood.
Colorectal cancer
Blood mixed into the stool, with a changed bowel habit and weight loss. Highly treatable when found early.
Inflammatory bowel disease
Blood with mucus and diarrhoea, often with cramping and weight loss in younger adults.
Peptic ulcer
Bleeding higher in the gut, appearing as black tarry stool rather than red blood.
How it is investigated
- ✓Examination including proctoscopy
- ✓Haemoglobin, to detect blood loss
- ✓Colonoscopy — the definitive test for lower gut bleeding
- ✓Upper GI endoscopy when the stool is black
Not every patient needs every test. The consultation decides which of these apply to you.
Frequently asked questions
It is probably just piles. Do I need a colonoscopy?▼
Piles are common and are the likeliest explanation, but they do not rule out something else in the same bowel. Colonoscopy is advised when blood is mixed through the stool, when bowel habit has changed for more than three weeks, when there is weight loss or anaemia, or over the age of 45.
What does black stool mean?▼
Black, tarry, strong-smelling stool usually means digested blood from the stomach or upper intestine, often from an ulcer. It is a medical emergency — go to an emergency department rather than waiting for an appointment. Iron tablets can also blacken stool, but this should not be assumed.
This page is general health information, not a diagnosis or a substitute for a consultation. Symptoms overlap between harmless and serious conditions, and only an examination can tell them apart. If you are worried, see a doctor.
Plan your first visit
Not sure which specialist to see? Tell our care team the reason for your visit and we will help you choose.
- Bring previous prescriptions, relevant test reports or scan images, a medication list and photo ID.
- If you plan to use insurance, bring your policy details. OPD, tests and admission benefits depend on your individual plan and approval.
- Your first consultation determines which tests or treatments are needed; not everyone needs every test listed on this page.
Appointments are requests until confirmed. In a medical emergency, call 044 2025 2025 or go to the nearest emergency department.