Causes of Mucus in Diarrhea

Medically Reviewed by Minesh Khatri, MD on September 14, 2023
Written by Stephanie Booth
4 min read

A small amount of mucus in your poop is normal, but there are times it could be a sign of a condition that needs treatment.

A layer of mucus lines and protects the inside of your large intestine (aka your colon). If this layer gets damaged, you'll see a lot more mucus in your stool. If you have diarrhea with mucus, inflammatory bowel disease or an infection could be to blame. It can be accompanied by blood and fevers.

In IBS, there's a breakdown between how your brain and gut talk to each other. When you have this condition, certain foods, stress, or changes in your hormones can make your colon spasm. This pushes food too quickly through your system and causes it to come out as watery or mucus-filled diarrhea.

Symptoms of IBS vary widely. Besides mucus-filled diarrhea, you could have:

  • Belly pain that doesn't go away or gets better after a bowel movement
  • Constipation, diarrhea, or both
  • Gas
  • Bloating
  • Belly swelling
  • Wanting to poop but feeling that you can't

Since changing what you eat helps many people with IBS, you may want to speak to a dietitian. Counseling and acupuncture can offer relief, and your doctor can prescribe medicines to ease your everyday symptoms.

Bacteria (and rarely viruses) that cause food poisoning and invade the colon lining can lead to mucus in the stool. Often accompanied by blood and/or fever. "Stomach flu" affects the upper GI tract and doesn't tend to cause mucus.

If you have mucus in your diarrhea because of an infection, you may also have symptoms such as:

You need to treat your digestive symptoms gently when you're sick. Stay away from caffeine, alcohol, and spicy or fatty foods. Sip water so you don't get dehydrated.

It's also wise to check in with your doctor. Though many infections that affect your gut go away on their own, sometimes you need antibiotics or medicine that can stop your diarrhea. And always see your doctor if you notice blood in your stool.

This inflammatory bowel disease (IBD) causes long-term inflammation and ulcers in your digestive tract. That's a tube that reaches from your mouth to your anus and includes the small intestine and colon.

Your small intestine and colon are likely to become inflamed when you have Crohn's disease. You may have diarrhea with mucus in it.

You might also have symptoms such as:

  • Blood in your stool
  • An urgent need to poop
  • A feeling that you can't get all your stool out
  • Stomach cramps
  • Constipation
  • Weight loss

If you think you have Crohn's, see your doctor. Though there's no way to get rid of it for good, Medications and changes to what you eat can ease your symptoms and stop your condition from getting worse. Some people need surgery.

Another type of inflammatory bowel disease, ulcerative colitis causes sores to form inside your colon and rectum. You could start to have mucus-filled diarrhea right before other symptoms start to flare.

Other common signs of UC include:

  • Cramps
  • Frequent need to poop
  • Blood in your stool
  • Belly soreness or pain
  • Fatigue

See your doctor if you have these symptoms. There's no cure for UC, but you can learn about treatments that manage your symptoms.

This genetic condition causes your body to make thick, sticky mucus that can build up in your lungs, pancreas, and intestines. People with CF can't digest fat very well. Instead, they poop it out.

If you have CF, you'll have loose, greasy stools. Other signs could include:

There's no cure for CF, but medicines can help clear extra mucus from your body, make sure you can breathe well, and help you fight off infections. CFTR modulators may help some people by targeting specific defects in the CFTR protein so that the protein can work properly and slow its progression. 

It's still unclear what causes cancer to grow in your colon or rectum, the tube that sends your stools to your anus. Severe UC or Crohn's can raise your risk. If you eat lots of foods that are high in fat and low in fiber or drink a lot of alcohol, you're also more likely to get colorectal cancer.

Besides mucus in your diarrhea, common symptoms are:

  • Constipation or pencil-thin stools
  • Cramps
  • Nausea
  • Gas
  • Bloating
  • Feeling like you can't get all your poop out
  • Bright or dark red blood in your stool
  • Low energy
  • Weight loss

If you have any of these signs, see your doctor right away. Surgery, chemotherapy, and radiation are options to treat colon cancer.