Diarrhea is a common symptom of diabetes and has a myriad possible causes. Diabetic diarrhea, a subtype of chronic diarrhea, typically occurs in people with severe insulin-dependent diabetes mellitus and who show signs of generalized neuropathy.¹^,²

The term specifically describes chronic diarrhea resulting from secondary effects of diabetic gastroenteropathy.³This is a common symptom of diabetes, particularly in those who have had diabetes for a long time or whose condition has been poorly managed.

diabetes and gi diseases list — Diabetes and GI Diseases

History & Epidemiology

Diabetic diarrhea was first recognized in 1936 by Bargen, Bollman, and Kepler in The “diarrhea of diabetes” and steatorrhea of pancreatic insufficiency.¹^,⁴ It described the unexplained bouts of diarrhea experienced by many people with severe diabetes.¹^,⁴ Despite the considerable amount of time that has elapsed since diabetic diarrhea was first recognized, there is a general dearth of research on the topic.³ As a result, the pathophysiological mechanisms that underlie it remain largely unknown.³

Chronic diarrhea comprises approximately half of all cases of diarrhea related to diabetes.³ Chronic diarrhea is defined as the occurrence of more than 3 liquid stools per day lasting for at least 4 weeks. Symptoms may first manifest anywhere between a few months to decades after the initial onset of diabetes, with a mean onset of 8 years.¹

The prevalence of diabetic diarrhea in the general population is estimated to range from 8% to 22%.³ However, these estimates may be skewed by symptomatic overlap with other gastrointestinal conditions; the actual prevalence is suspected to be much lower.³

Diabetes and Diarrhea Causes & Risk Factors

Although the underlying physiological processes behind diabetic diarrhea are not well understood, there are commonalities between a patient’s symptoms and medical history that are suggestive of a mechanism. Diabetic diarrhea most often affects people whose diabetes is poorly managed for an extensive period of time and patients with evidence of generalized neuropathy.¹^,⁵ High blood glucose levels that result from the poor management of the condition can also lead to nerve damage and diabetic autonomic neuropathy, a condition common among people with diabetes-induced diarrhea.⁵

Autonomic neuropathy is known to cause disturbances in gastrointestinal motility, suggestive of its role in diarrhea.² Peripheral neuropathy is also present in many cases of patients with diabetic diarrhea, which further points to diabetes-related neuropathy as a risk factor.⁶

Nonetheless, diabetic diarrhea is not exclusive to people with peripheral or autonomic neuropathy. Bacterial overgrowth and pancreatic exocrine insufficiency have both been suggested as possible underlying conditions that could explain diabetic diarrhea, but no consistent etiology has been identified.⁶ Diabetic diarrhea is also more common in cases of type 1 diabetes than in type 2, and slightly more common in men than in women.¹^,²

Prognosis of Diabetic Diarrhea

As with other forms of chronic diarrhea, diabetic diarrhea is closely associated with impaired nutrition.⁷ This may worsen poorly controlled blood glucose, which can, in turn, intensify autonomic or peripheral neuropathy and associated symptoms. It may also lead to neuropathy where it is not already present.⁸^,⁹

If untreated, bouts of diabetic diarrhea can last for several weeks or longer, then alternate with periods of normal bowel movements, constipation, or both.¹^,⁶^,⁷ Diarrhea in diabetes can be difficult to effectively treat and manage.⁶

Diabetic Diarrhea Diagnosis & Presentation

Like chronic diarrhea, diabetic diarrhea involves bouts of diarrhea that last for 4 weeks or more, with loose stools occurring more than 3 times a day.⁷ Severe diarrhea that is watery, voluminous, and brown in color is also common, as is steatorrhea.¹ The bouts of diarrhea may be intermittent, with periods of normal bowel movements or constipation in between.⁶ The diarrhea is generally painless and may happen at any time of day, but usually at night.¹

Fecal incontinence is common alongside diarrhea in diabetes, especially at night.¹ The patient may experience tenesmus, most often accompanying severe diarrhea.¹ Some patients experience signs of impaired gastric emptying, including nausea and vomiting.¹

Symptoms of associated peripheral or autonomic neuropathy are present in most cases of diabetic diarrhea.¹ These can include but are not limited to increased sensitivity to pain, numbness, muscle weakness, loss of appetite, nausea, decreased sexual function, retrograde ejaculation, orthostatic hypotension, gustatory sweating, and bladder dysfunction.¹^,¹⁰

Diagnostic Workup

Diagnosis of diabetic diarrhea involves careful clinical assessment. Once it has been established that the patient’s diarrhea is chronic and that long-term or poorly managed diabetes is present, the patient’s medical history and a physical exam will help to identify suggestive symptoms. Anorectal examination can identify loss of sphincter control that may point to characteristic neuropathy.¹

A follow-up series of stepwise laboratory tests can rule out other conditions.¹¹ Endoscopy and biopsy may also help if initial testing does not confirm a diagnosis.¹¹ Upper and lower gastrointestinal endoscopies may be used, depending on the specific symptoms.¹¹

Differential Diagnosis of Diarrhea in Diabetes

Due to the range of symptoms and significant overlap with other diabetes-related diarrheal conditions, it can be difficult to confirm cases of diabetic diarrhea. The combination of the symptoms noted above, particularly those associated with neuropathy, are important during clinical assessment and may point to the need for follow-up testing.

Conditions that may cause similar chronic diarrhea and related symptoms, especially the most visible symptoms, include but are not limited to, coeliac disease, irritable bowel syndrome (IBS), and drug-related diarrhea. Stools that are painful and contain blood suggest that IBS is more likely, and can be confirmed with a lower gastrointestinal endoscopy or biopsy.¹¹ Signs of long-term malabsorption and symptoms triggered by consuming gluten might point to celiac disease, which can be confirmed with an upper gastrointestinal endoscopy.¹¹^,¹²

Various drugs, including those commonly used to treat diabetes, may also cause chronic diarrhea symptoms. Metformin is a common first-line medication for type 2 diabetes that reduces blood glucose produced by the liver. Diarrhea is a common side effect of metformin, affecting around 30% of patients.³^,¹³

References

Valdovinos MA, Camilleri M, Zimmerman BR. Chronic Diarrhea in Diabetes Mellitus. Mayo Clin Proc. 1993;68(7):691-702. doi:0.1016/S0025-6196(12)60606-5
Hoegenauer C, Hammer HF. Maldigestion and Malabsorption. In: Feldman M, ed. Sleisenger and Fordtran’s Gastrointestinal and Liver Disease. 11^th ed. Elsevier; 2021:1677-1710
Sangnes DA, Dimcevski G, Frey J, Softeland E. Diabetic Diarrhea. J Intern Med. 2021;290(6):1206-1218. doi:10.1111/joim.13340
The “diarrhea of diabetes” and steatorrhea of pancreatic insufficiency. Mayo Clin Proc. 1936; 11: 737-742
Frieling T. Diabetic autonomic neuropathy of the gastrointestinal tract. UpToDate. Published August 10, 2022. Accessed Oct 10, 2022. https://www.uptodate.com/contents/diabetic-autonomic-neuropathy-of-the-gastrointestinal-tract#H921993962
Ogbonnaya KI, Arem R. Diabetic diarrhea. Arch Intern Med. 1990;150(2):262-267. doi:10.1001/archinte.150.2.262
Guz-Mark A, Shamir R. Chronic Diarrhea. In: Kliegman RM, ed. Nelson Textbook of Pediatrics. 21^st ed. Elsevier; 2020:2033-2041
Stevens D, Quan D. Diabetic Neuropathies. In: McDermott MT, ed. Diabetes Secrets. Elsevier; 2022:34-39
Reynolds A, Mann J. Update on Nutrition in Diabetes Management. Med Clin North Am. 2022;106(5):865-879. doi:10.1016/j.mcna.2022.03.003
Diabetes and Nerve Damage. Centers for Disease Control and Prevention website. Updated June 20, 2022. Accessed Oct 10, 2022. https://www.cdc.gov/diabetes/library/features/diabetes-nerve-damage.html
Pasricha PJ. Gastrointestinal Endoscopy. In: Goldman L, ed. Goldman-Cecil Medicine. 26^th ed. Elsevier; 2020:834-840
Cardenas A, Kelly CP. Celiac Sprue. Semin Gastrointest 2002;13(4):232-244
Corcoran C, Jacobs TF. Metformin. StatPearls. NCBI Bookshelf version. StatPearls Publishing; 2022. Accessed Oct 10, 2022

Author Bio

Martyn Bryson is a medical writer living in Philadelphia, Pennsylvania. They have over a decade of experience as a writer and editor covering a wide range of health and wellness topics.