A recent study conducted at Giresun University investigated the antidiabetic activity of ethanolic propolis extracts in vivo and in-vitro. The trial involved four groups of five rats each; the control group was given distilled water orally, and diabetic ones received 30% or 15% propolis extract at a dosage of 0.5 ml/100 g for 4 weeks. The results of the study showed a decrease in blood glucose levels from 393±192.7 to 154±28.0 mg/dl and from 386±141.1 to 331.5±123.74 mg/dl in rats treated with 30% and 15% propolis, respectively.
Besides, the authors observed an improvement in both groups treated with propolis at the pancreatic, hepatic, and renal tissue levels. It was also noted that the decrease in blood sugar level was more noticeable in groups fed with 30% propolis. The scientists suggested that propolis is a remarkable natural product with clinical potential in the treatment of diabetic disease.

Reference: El Adaouia Taleb, Rabia, et al. “In vivo and in vitro anti‐diabetic activity of ethanolic propolis extract.” Journal of Food Biochemistry: e13267.