Ulcerative Colitis and Blood in Your Stool

Medically Reviewed by Melinda Ratini, MS, DO on June 20, 2022
4 min read

If you have ulcerative colitis, you might see blood and mucus in your poop when you have a flare-up. It shows up most often in very loose, watery stools. This bloody diarrhea tends to happen with belly cramps, a sudden urge to have a bowel movement, and sometimes fever.

“Normal” seeming poop can have blood in it too, if your rectum or sigmoid colon contains areas of UC.

Your sigmoid colon is the part of your large intestine that connects to the rectum. A mix of mucus and blood can come out during or between bowel movements.

The farther up your large intestine your UC goes, the looser your stools are likely to be. You might have more than 10 bowel movements a day during an attack. Often, stools are composed only of blood and pus.

Frequent diarrhea means your colon has to empty a lot. The cells that line the organ shed each time. This erosion causes open sores. Usually, the blood in your stools comes from these ulcers.

Another reason for bleeding caused by having so many bowel movements is an anal fissure. This is a tear in your anus lining that can be painful, especially when you poop. You might see bright red blood in your stool or on your bathroom tissue when you wipe.

Some bleeding is a common symptom of UC. There’s a wide range between harmless and dangerous, though. On one end, a mild attack might prompt several bowel movements per day, with blood in your stool appearing sometimes.

A serious flare-up could mean six or more bowel movements per day, with blood showing up most of the time. An extreme attack might measure more than 10 bloody poops in one day. This is called fulminant ulcerative colitis.

A hemorrhage, meaning severe bleeding, is rare but life-threatening. Only about 3% of people with UC, and 0.1 to 1.4% of hospital admissions for UC, will have this complication. It’s a dangerous flare that requires an urgent colectomy, or surgery to remove all or part of your colon. About 10% of urgent colectomies are due to UC.

You should call your doctor right away if:

  • Your diarrhea is heavy and constant.
  • You see blood clots in your stool and blood is coming from your anus.
  • Your fever spikes.
  • You’re in pain.

You need emergency care if:

  • You’re bleeding and feel faint.
  • You have severe bleeding.
  • You’re vomiting blood.

Some anti-inflammatory drugs can help manage, or even stop, bleeding. So blood in your stools might be a sign you need to talk to your doctor about tweaking your meds.

Too much blood loss can cause anemia, which means you don’t have enough blood to transport oxygen through your body. About 1 in 3 people with UC have anemia. Symptoms include:

UC leads to anemia because blood loss makes you lose iron your body needs. Also, when your intestines swell over time, your body has a hard time absorbing iron, as well as other key vitamins and minerals like folic acid and B12.

Your doctor will likely treat your anemia with iron supplements, changes to your diet, or even a blood transfusion. You might continue to take iron supplements to prevent anemia in the future.

You can treat an anal tear at home in several ways:

  • Eat a high-fiber diet and take over-the-counter supplements to bulk up and soften your stools.
  • Take sitz baths – aka soak your bottom in a warm tub – several times a day. This will relax your anal sphincter muscles and soothe the painful area. Your sphincter is the ring-like muscle at the opening of your anus. It works to let stools pass.
  • Drink more water.
  • Use topical ointments or other meds your doctor prescribes.

You likely won’t need surgery for an anal fissure, unless it’s ongoing. In that case, your surgeon might inject Botox into your anal sphincter, or cut a small part of the muscle to relax it and lessen spasms and pain.

Up to a third of people with UC may need surgery if treatment isn’t working or a complication arises, like a hemorrhage. Your doctor will choose the type of surgery based on your age and health.

The first type removes your colon and rectum. Your surgeon will make a stoma, aka an ileostomy, which is an opening in your abdominal wall that links into your digestive system. Your body waste will go into a pouch outside your body, which you can attach with special adhesive.

A newer surgery removes the colon, but puts a pouch inside your body. It connects your small bowel to your anal sphincter muscle. This keeps your bowel intact without having to wear an outer device.