Patients who develop frequent diarrhea after starting medication prescribed following a diabetes diagnosis often wonder whether the drugs are to blame. They worry about whether it is safe to keep taking them, or whether the diabetes itself has worsened. Some diabetes medications can indeed cause diarrhea. But diarrhea is not a typical early symptom of diabetes, and not all cases of diarrhea in patients stem from diabetes or its treatment. Patients should compare when they first took the drug or increased the dose with when symptoms appeared. If the diarrhea persists, other causes need to be examined as well.
Metformin, widely used to treat diabetes, can cause abdominal discomfort or diarrhea in the early stages of treatment or after a dose increase. Alpha-glucosidase inhibitors, which slow the digestion and absorption of carbohydrates, can also cause diarrhea. Unabsorbed carbohydrates ferment in the intestine, which can lead to gas or loose stools.
The same applies to GLP-1 drugs, which can cause gastrointestinal symptoms including nausea, diarrhea and constipation. These symptoms tend to appear early in treatment or while the dose is being raised, and they often ease over time.
If medication is the suspected cause, patients can consult their doctor about adjusting how they take the drug or changing the prescription. With metformin, options include taking it with meals or raising the dose gradually. Switching to an extended-release formulation, which releases the drug slowly, is another option. For GLP-1 drugs, doctors can delay a planned dose increase or adjust the dose depending on symptoms. Rather than stopping the medication on their own or simply enduring the symptoms, patients should tell their doctor precisely when the diarrhea began and how severe it is.
If diarrhea continues, patients need to replace fluids and electrolytes. Cutting back on greasy or spicy foods and alcohol, which can worsen symptoms, is advisable. When diarrhea and vomiting are severe enough to make eating and drinking difficult, dehydration can follow, affecting blood sugar levels and kidney function. In such cases, some diabetes medications may need to be temporarily stopped or adjusted, so patients should seek medical attention quickly and follow their doctor's instructions on dosing.
Eating habits deserve as much attention as medication. Patients who have switched their usual snacks to sugar-free products to manage blood sugar after a diabetes diagnosis should check the ingredient labels.
Sugar alcohols such as sorbitol, xylitol and maltitol, used in sugar-free candy and gum, can cause diarrhea when consumed in large amounts. Poorly absorbed in the intestine, they draw in water and loosen stools. Rather than taking comfort in a "sugar-free" label, consumers should check which sweeteners a product contains and how much they are consuming. Those who have been eating products with sugar alcohols frequently can try cutting back and see whether the diarrhea changes.
The search for a cause should not be narrowed to diabetes drugs or snacks alone. Causes of diarrhea that occur in people without diabetes can affect patients with diabetes just as readily. Infectious enteritis, irritable bowel syndrome and inflammatory bowel disease are possibilities, as are intolerance to certain foods and disorders of digestion or absorption.
Bile acid diarrhea, pancreatic disease, small intestinal bacterial overgrowth and hyperthyroidism also need to be ruled out. A history of gallbladder removal is worth checking. Other medications and dietary supplements taken alongside diabetes drugs, excessive use of laxatives and frequent drinking can also cause diarrhea or make it worse.
In patients who have had diabetes for many years, diabetic autonomic neuropathy is another possible cause. When the autonomic nerves that regulate bowel movement are damaged, loose stools can recur without significant abdominal pain, or diarrhea can occur at night. Constipation and diarrhea may alternate, and some patients also experience fecal incontinence, in which they cannot hold their stool.
These symptoms alone, however, are not enough to diagnose diabetic autonomic neuropathy. Other causes must be ruled out first. In particular, when diarrhea develops in a patient diagnosed with diabetes only recently, doctors generally look first at drug side effects or common gastrointestinal conditions rather than autonomic neuropathy.
Patients visiting a hospital for persistent diarrhea can help by organizing their symptoms beforehand. It is useful to record the date the diarrhea began, how many times a day it occurs and whether it happens at night. Recent meals, any new medications or dose changes and recent travel are also important information for identifying the cause. Patients should also note any weight loss, blood in the stool, fever or abdominal pain. Depending on the symptoms, doctors may order blood and stool tests.
