How does lactulose affect blood glucose levels in diabetic patients?

From the Guidelines

Diabetics should be careful when taking lactulose, but it is generally considered safe and has minimal impact on blood glucose levels, as it is not significantly absorbed in the intestine and does not contribute to blood glucose elevation like other sugars would. The use of lactulose in mildly constipated, noninsulin-dependent patients with diabetes mellitus type 2 may not lead to an increase in blood sugar levels, as stated in a recent clinical practice guideline 1. Lactulose is a synthetic disaccharide that exerts an osmotic laxative effect in the colon, and its mechanism of action is primarily within the intestinal lumen rather than systemic circulation.

Some key points to consider when using lactulose in diabetic patients include:

• The small amount of lactulose that might be absorbed (less than 3%) is metabolized by the liver and does not significantly affect blood glucose control 1.
• Some commercial lactulose preparations may contain small amounts of other sugars like lactose or galactose, which could theoretically have a minor effect on blood glucose.
• Patients should still monitor their blood glucose levels when starting lactulose, especially those with poorly controlled diabetes.
• Major adjustments to diabetes medication regimens are typically unnecessary when using lactulose for conditions like constipation or hepatic encephalopathy.

The standard dosing of lactulose (15-30 mL once or twice daily for constipation) can be used without significant dose adjustments in diabetic patients, as long as they are monitored for any potential effects on blood glucose levels 1. Overall, lactulose is considered a safe and effective treatment option for constipation in diabetic patients, with minimal impact on blood glucose control.

From the FDA Drug Label

Since lactulose solution contains galactose (less than 1.6 g/15 mL) and lactose (less than 1.2 g/15 mL) it should be used with caution in diabetics.

Diabetics should be careful when taking lactulose because it contains galactose and lactose, which may affect their blood glucose levels. The drug label recommends using lactulose with caution in diabetic patients 2.

From the Research

Blood Glucose Response to Lactulose in Diabetic Patients

• The effect of lactulose on blood glucose levels in diabetic patients has been studied in several research papers 3, 4, 5, 6.
• A study published in the World Journal of Diabetes in 2021 found that lactulose did not significantly affect blood glucose levels in mildly constipated, non-insulin-dependent subjects with type 2 diabetes mellitus (T2DM) 3.
• The study compared the blood glucose response after oral intake of 20g and 30g lactulose with water and 30g glucose, and found that lactulose formulations showed comparable results to water, with a minor increase in maximum blood glucose level after the 30g dose of liquid lactulose 3.
• Another study published in Frontiers in Endocrinology in 2022 suggested that lactulose may have a role in the management and prevention of type 2 diabetes via its actions on the gut microbiota 4.
• The study found that lactulose increased the abundance of short-chain fatty acid (SCFA)-producing bacteria, such as Lactobacillus and Bifidobacterium, and suppressed potentially pathogenic bacteria, such as Escherichia coli 4.
• A review published in Biochemical Pharmacology in 2025 discussed the potential mechanisms by which short-chain fatty acids, produced by the gut microbiota, may influence the pathogenesis of type 2 diabetes mellitus (T2DM) and insulin resistance 7.

Carbohydrate Impurities in Lactulose

• Lactulose products contain carbohydrate impurities, such as lactose, fructose, and galactose, which occur during the manufacturing process 3, 5.
• However, studies have shown that these impurities do not significantly affect blood glucose levels in healthy subjects or diabetic patients 3, 5.
• A study published in the World Journal of Gastrointestinal Pharmacology and Therapeutics in 2018 found that the blood glucose concentration-time curves after intake of 10g and 20g lactulose were almost identical to those after water intake, despite the different amounts of carbohydrate impurities 5.

Clinical Implications

• The findings of these studies suggest that lactulose may be a safe and effective treatment option for constipation in diabetic patients, without significantly affecting blood glucose levels 3, 5.
• However, further research is needed to fully understand the effects of lactulose on blood glucose levels and its potential role in the management and prevention of type 2 diabetes 4, 7.