High blood sugar, known as hyperglycemia, impacts various body systems. When the body cannot effectively process glucose, the excess sugar can cause long-term damage and acute symptoms. While diabetes is often associated with cardiovascular and nerve complications, gastrointestinal issues are also a frequent concern. Digestive complaints, particularly chronic diarrhea, affect up to 20% of people with diabetes.
The Direct Link Between High Blood Sugar and Diarrhea
Acute episodes of high blood glucose can trigger osmotic diarrhea. This mechanism relies on the principle that sugar attracts water across a semipermeable membrane. When blood sugar levels are significantly elevated, unabsorbed glucose may be present in the intestinal tract.
This unabsorbed glucose acts as an osmotically active substance within the intestinal lumen. As the concentration of solutes inside the bowel increases, water is drawn from the body’s tissues into the intestine. This influx of water results in loose, watery stools and the characteristic frequency of osmotic diarrhea. A similar effect occurs with the consumption of sugar alcohols, which are poorly absorbed and can also pull water into the bowel.
Long-Term Effects on the Digestive System
A chronic cause of diarrhea in people with diabetes is diabetic enteropathy, which stems from nerve damage. Prolonged exposure to high glucose levels can damage the autonomic nervous system, which controls involuntary bodily functions like digestion. When the nerves supplying the digestive tract are affected, this is called autonomic neuropathy.
This nerve damage disrupts the coordination of peristalsis, the muscle contractions that move food through the intestines. Abnormal motility can cause food to move too slowly or too quickly, resulting in diarrhea. Diarrhea related to diabetic enteropathy is often painless, watery, explosive, and frequently occurs at night. Neuropathy can also impair the function of the anal sphincter, leading to fecal incontinence.
Secondary Causes of Diarrhea in Diabetic Patients
Diarrhea in individuals with diabetes is often multi-factorial, meaning it can be caused by reasons beyond the direct osmotic and neuropathic effects.
Medications
A common secondary cause is the side effect profile of certain diabetes medications, such as Metformin. This drug can cause gastrointestinal upset, including diarrhea, typically early in treatment.
Small Intestinal Bacterial Overgrowth (SIBO)
The altered motility caused by neuropathy can contribute to SIBO. When the movement of the small intestine slows down, bacteria from the large intestine can migrate upward and multiply. This leads to malabsorption, gas, bloating, and diarrhea.
Autoimmune Conditions
People with Type 1 diabetes have a higher prevalence of other autoimmune conditions, such as Celiac disease. Celiac disease causes an immune reaction to gluten that damages the small intestine lining, resulting in chronic diarrhea if untreated.
Exocrine Pancreatic Insufficiency (EPI)
Another contributing factor is Exocrine Pancreatic Insufficiency (EPI), where the pancreas does not produce sufficient digestive enzymes. This lack of enzymes impairs the breakdown and absorption of fats, resulting in fatty stools and diarrhea. Identifying these secondary causes is crucial for effective treatment.
Managing Diarrhea and When to Seek Help
The most important long-term strategy for managing diarrhea related to high blood sugar is achieving stable glucose control. Maintaining blood sugar levels within the target range helps prevent the progression of nerve damage and reduces the severity or frequency of acute osmotic episodes. A healthcare provider may recommend dietary changes, such as limiting foods containing poorly absorbed sugar alcohols and increasing the intake of soluble fiber to help solidify stools.
Immediate management involves preventing dehydration, which is a substantial risk during episodes of diarrhea. Drinking plenty of water and electrolyte solutions is necessary to replace lost fluids and minerals. Over-the-counter anti-diarrheal medications, like loperamide, may be used temporarily to slow gut motility and allow for increased water absorption, but only under a doctor’s guidance.
Seek medical attention if diarrhea is persistent, lasting longer than 48 hours, or if it is accompanied by concerning symptoms. Warning signs include fever, severe abdominal pain, or the presence of blood in the stool. These symptoms may indicate an underlying infection or a more serious complication that requires immediate diagnostic testing and specific treatment.