Causes of Diarrhea in Diabetes (Diabetic Diarrhea)

Diabetes and Diarrhea

In both diabetes type 1 and type 2, diarrhea (loose bowel movements) may appear from several reasons:

1. Usual Causes of Diarrhea

There are several causes of acute (sudden) diarrhea, and chronic diarrhea that can affect anyone including diabetics.

2. Sugar-Free Foods

“Low-calorie foods” , “Diet soda”, “sugar-free” chewing gum or candies, or any sweetened food product may contain sorbitol, xylitol, maltitol, mannitol or other“polyols” (check labels!) that, if ingested in excess, may cause diarrhea, especially in a person with fructose malabsorption.

3. Medications

Medications, often used by diabetics, that may cause diarrhea:

  • Metformin, a sugar lowering drug used in diabetes type 2, especially if taken on an empty stomach, can cause diarrhea. After some time, diarrhea often resolves by itself, and if not, the drug has to be changed.

4. Small Intestinal Bacterial Overgrowth (SIBO)

In the healthy small intestine there are usually some normal bacteria (normal intestinal flora), but in diabetes, due to changed intestinal motility, they may overgrow, and cause bloating and diarrhea.

Diagnosis of SIBO is with a breath test. SIBO is treated with antibiotics, and Metclopropamide and cisapride may help to accelerate the passage of fluids through the small intestine, thus preventing the SIBO itself (1).

4. Damaged Abdominal Nerves

Long lasting (several years) poorly controlled diabetes (elevated blood glucose) may affect bowel nerves and thus bowel motility (peristalsis), what usually results in chronic diarrhea or, rarely, in constipation. The condition is called autonomic neuropathy (autonomic from autonomic nerves that control muscle contractions in the bowel; neuropathy = nerve damage). This kind of nerve damage is permanent, and can’t be corrected, but it can be prevented with early and regular treatment of diabetes.

Beside bowel nerves damage, hands/feet nerves causing hand/feet burning/tingling commonly occurs at the same time, what can help in diagnosis.

5. Damaged Abdominal Arteries

Long lasting elevated blood glucose may damage the inner layer of the arteries that supply the bowel, thus causing their hardening (sclerosis) and narrowing. The condition is called abdominal arteriosclerosis and can result in ischemic colitis (from ischemia = reduced blood supply; colitis = inflammation of the colon) with the lower left side abdominal pain and bloody diarrhea.

Arteriosclerosis of the abdominal vessels is confirmed by angiography – an X-ray or CT of abdominal vessels, after injecting contrast substance into the circulation.

6. Celiac Disease

Celiac disease is often associated with diabetes from unknown reasons. Diarrhea appears after ingesting any food containing gluten.

7. Chronic Pancreatitis

Chronic pancreatitis often develops in diabetics, but it rarely causes symptoms: upper central or left abdominal pain and loose, whitish, sticky, foul smelling bowel movements (1).

History of upper abdominal pain, pancreatic enzymes in the blood, stool test for fat, ultrasound, and CT may help in diagnosis of chronic pancreatitis.


  1. Small intestinal bacterial overgrowth, diarrhea and other gut disorders related to diabetes  (
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