Blood in Stool: Causes and Red Flags
Seeing blood in your stool is understandably worrying. Often the cause is something minor and treatable, like hemorrhoids — but because blood can occasionally signal something that needs treatment, it's a symptom that should always be evaluated by a healthcare professional.
Bright red vs dark blood
The color offers a clue about where bleeding is coming from:
- Bright red — often from the lower bowel, rectum, or anus (for example hemorrhoids or a small tear). It may streak the stool, appear on toilet paper, or color the water.
- Dark red or maroon — can come from higher in the colon.
- Black and tarry — suggests bleeding higher up, in the stomach or small intestine (see black stool).
Common causes
- Hemorrhoids — swollen veins in the anus; a very common cause of bright red blood.
- Anal fissures — small tears, often from hard stool, that can cause pain and bright red blood.
- Inflammation or infection — conditions affecting the bowel can cause bleeding.
- Polyps or other growths — less common, which is exactly why blood should be evaluated rather than assumed harmless.
Why it should always be checked
Most rectal bleeding is from a minor cause. But because the same symptom can occasionally point to something that benefits from early treatment, doctors recommend having any blood in the stool assessed — especially if it's new, persistent, or comes with other symptoms. Getting it checked is reassurance if it's minor and important if it isn't.
See a doctor promptly if you have
- A large amount of blood, or bleeding that doesn't stop
- Black, tarry stool
- Blood with dizziness, weakness, or fast heartbeat
- Blood with abdominal pain, unexplained weight loss, or a change in bowel habits
- Any rectal bleeding if you're over 50 or have a family history of bowel disease
Track it with PoopID
A clear record of when and how often you notice blood helps your doctor. PoopID lets you log changes alongside your Bristol type and color. For the full picture of stool colors, see our stool color chart.
- Sources:
- NIDDK — Gastrointestinal bleeding. niddk.nih.gov
- NHS — Blood in stool / rectal bleeding. nhs.uk
Frequently asked questions
Is blood in stool always serious?
No. It's frequently caused by hemorrhoids or small tears. But because it can occasionally signal something that needs treatment, any blood in the stool should be evaluated by a doctor.
What does bright red blood in stool mean?
Bright red usually comes from lower in the gut — the rectum or anus — such as hemorrhoids or an anal fissure. It still should be checked, especially if new or persistent.
What's the difference between red blood and black stool?
Bright red usually means bleeding lower down; black, tarry stool suggests bleeding higher up in the stomach or small intestine, where blood is partly digested.
When is rectal bleeding an emergency?
Seek urgent care for a large amount of blood, bleeding that won't stop, black tarry stool, or blood with dizziness, weakness, severe pain, or a fast heartbeat.
This article is for general information only and is not medical advice. Consult a qualified healthcare professional about any symptom that concerns you.