In a preliminary trial, administration of Ginkgo biloba extract (120 mg per day) for three months to patients with type 2 diabetes who were taking oral anti-diabetes medication resulted in a significant worsening of glucose tolerance. Ginkgo did not impair glucose tolerance in individuals whose diabetes was controlled by diet. Individuals taking oral anti-diabetes medication should consult a doctor before taking Ginkgo biloba.

Supplementation with large amounts of niacin (also called nicotinic acid) can increase blood glucose levels in diabetics, which might interfere with the blood-sugar-lowering effects of repaglinide. The form of vitamin B3 known as niacinamide does not have this effect. People who start or stop supplementing niacin while on repaglinide should carefully monitor their blood sugar levels and consult their prescribing doctor about making adjustments in the daily amount of drug taken.

Willow bark contains salicin, which is related to aspirin. Both salicin and aspirin produce anti-inflammatory effects after they have been converted to salicylic acid in the body. Taking aspirin together with repaglinide enhances the blood-sugar-lowering effects of the drug, which might result in unwanted side effects. Controlled research is needed to determine whether taking willow bark together with repaglinide might produce similar effects.