Late-Onset Chronic Severe Painless Diarrhea Secondary to Metformin: Case Report and Literature Review

Abstract

We present a case of late-onset chronic severe painless diarrhea in an 80-year-old man with type 2 diabetes who was on metformin for 5 years. He underwent multiple laboratory and imaging investigations with no underlying cause found. After detailed medication review, a trial of metformin discontinuation resulted in immediate resolution of symptoms. This case highlights the importance of considering metformin as a cause of new-onset diarrhea in patients even if they had previously tolerated the drug well for years, as its discontinuation can potentially prevent patient inconvenience and discomfort associated with unnecessary investigations.

Metformin-Induced Chronic Diarrhea Misdiagnosed as Irritable Bowel Syndrome for Years

“…Metformin-induced diarrhea is mainly due to changes in the gut microbiome, increased intestinal glucose and bile acid turnover, and increased GLP-1 concentration. Decreased ileal bile salt reabsorption enhances the secretory effect of bile salts in the colon and increases intestinal motility with malabsorption [ 7 ]. Metformin-induced weight loss has been postulated as the result of alteration in leptin-associated adipocyte metabolism as well as a reduction of carbohydrate absorption from the gut [ 8 ].…”

A Common Drug Causing a Common Side Effect at an Uncommon Time: Metformin-Induced Chronic Diarrhea and Weight Loss After Years of Treatment

“…Case reports of late-onset diarrhea in type 2 diabetes and in those with stable doses of metformin therapy for several years are scarce (6,7). In one report, there was no obvious precipitant factor, whereas in the other, polypharmacy with ranitidine and digoxin and nephropathy were attributed to increased metformin levels causing diarrhea.…”