What are the most common causes of blood in stool?
The most common blood in stool causes are hemorrhoids and anal fissures, which usually cause bright red blood on the toilet paper. Other causes include diverticular bleeding, colon polyps, inflammatory bowel disease, infections, peptic ulcers and, less commonly, colorectal cancer. Any rectal bleeding should be checked by a doctor, because the cause cannot be confirmed by appearance alone.
What the color of blood tells you
- Bright redUsually from the rectum or anus: hemorrhoids, fissures, low polyps.
- Dark red or maroonOften from the colon or small intestine: diverticula, colitis, polyps.
- Black and tarryUsually upper GI bleeding: ulcers, gastritis. Needs urgent care.
Which blood in stool causes are serious?
The causes that need prompt attention are bleeding ulcers, diverticular bleeding, inflammatory bowel disease, ischemic colitis, polyps and colorectal cancer. Warning signs that bleeding is serious include black stools, large amounts of blood, clots, dizziness, a change in bowel habits, weight loss and anemia.
| Cause | Typical bleeding | Other clues |
|---|---|---|
| Hemorrhoids | Bright red on paper or in the bowl | Itching, swelling, straining |
| Anal fissure | Bright red streaks | Sharp pain during bowel movements |
| Diverticular bleeding | Sudden, painless, can be heavy | Older age, known diverticulosis |
| Colon polyps or cancer | Often small or hidden | Anemia, bowel changes, weight loss |
| Ulcerative colitis or Crohn's | Blood mixed with diarrhea or mucus | Urgency, cramping |
| Peptic ulcer | Black, tarry stools | Upper abdominal pain, NSAID use |
Call 911 or go to the ER if you have
- Large amounts of blood or passing clots
- Black, tarry stools with weakness
- Dizziness, fainting or a racing heart
- Severe abdominal pain
- Vomiting blood
Have symptoms like these?
Dr. Muhammad Ali Khan, a board-certified gastroenterologist and hepatologist, sees adults at our Katy and Cypress offices, serving patients across Greater Houston.
Can foods or medicines change stool color?
Yes. Beets, red gelatin, tomato skins and red food coloring can make stool look red, while iron tablets and bismuth medicines such as Pepto-Bismol can turn it black. If you are not sure whether it is blood, a doctor can test the stool. Black stool without a clear cause should always be checked. See our stool color chart.
How is the cause of blood in stool found?
The doctor takes a history, examines the anus and rectum, and checks a blood count for anemia. Colonoscopy is the main test for bleeding from the colon and rectum and can treat many causes, such as removing polyps or treating hemorrhoids. Upper endoscopy is used for black stools. Capsule endoscopy may be used if the source is in the small intestine.
Tip: Note the color of the blood, whether it is on the paper, in the water or mixed into the stool, and how often it happens. These details help your doctor decide how urgent testing is.
When should you see a gastroenterologist?
See a gastroenterologist for any rectal bleeding that is new, keeps returning, comes with bowel changes, pain, anemia or weight loss, or happens after age 45. Dr. Muhammad Ali Khan evaluates rectal bleeding for patients from Katy, Cypress, Fulshear, Richmond and Greater Houston. See our blood in stool specialist page and when to see a gastroenterologist for blood in stool.
Get answers instead of guessing
Request a visit with Dr. Muhammad Ali Khan at our Katy and Cypress offices. Most major insurance plans are accepted and self-pay options are available.
Key takeaways
- Hemorrhoids and fissures are the most common blood in stool causes.
- Bright red, maroon and black blood point to different sources.
- Polyps, IBD, ulcers and colorectal cancer also cause bleeding.
- Colonoscopy is the main test to find the cause.
- Heavy bleeding, clots or dizziness need emergency care.
Frequently asked questions
Is blood in stool always serious?
No, most cases are from hemorrhoids or fissures, but it should always be checked to rule out more serious causes.
Can constipation cause blood in stool?
Yes. Straining and hard stools can cause hemorrhoids and fissures that bleed.
Can stress cause blood in stool?
Stress does not directly cause bleeding but can worsen conditions such as IBD.
Is blood in stool a sign of colon cancer?
It can be, which is why bleeding should be evaluated, especially with bowel changes or after age 45.
Do I need a colonoscopy for blood in stool?
Often, yes, especially if you are 45 or older, have risk factors or the bleeding keeps returning.
Do I need a referral to see a gastroenterologist in Katy or Cypress?
It depends on your insurance plan. Many PPO plans let you book a specialist directly, while some HMO plans require a referral from your primary care doctor. Call (346) 340-4414 and the team can help you check.
Sources
- NIDDK — Gastrointestinal bleeding
- MedlinePlus — Gastrointestinal bleeding
- NIDDK — Diverticular disease
- MedlinePlus — Colorectal cancer
- NIDDK — Colonoscopy
Where to be seen in Katy and Cypress
United Gastroenterology Associates has two offices: Katy, at 23920 Katy Freeway, Suite 555, next to Memorial Hermann Katy Hospital, and Cypress, at 21216 Northwest Freeway, Suite 640, on US-290. Both are open Monday through Friday, 8:30 AM to 5:00 PM, closed for lunch from 12:00 to 1:30 PM, and serve patients from Fulshear, Richmond and across Greater Houston. Call (346) 340-4414 for either office.
Katy office
23920 Katy Freeway, Suite 555
Katy, TX 77494
Memorial Hermann Medical Plaza 1
Next steps
If you are dealing with blood in stool causes or any ongoing digestive concern, a focused evaluation can find the cause and start the right treatment. Dr. Muhammad Ali Khan and the team at United Gastroenterology Associates see adults from Katy, Cypress, Fulshear, Richmond, Greater Houston and across Texas. Call (346) 340-4414 or request an appointment today.
If you have severe pain, vomit blood, pass black stools or have chest pain, call 911 or go to the nearest emergency room.
