Oral carbohydrate administration tests were performed in tilapia. Either glucoseor starch in gelatin capsules were administrated orally after the tilapia were put on a fast for 24h. Blood was sampled at selected time intervals from 1 to 12h thereafter. The concentration of plasma glucose of tilapia peaked at 3 h after oral ingestion of both carbohydrates. Plasma insulin concentration in tilapiaingested with glucose was higher (p<0.05) at 1h after oral administration than those ingestedwith starch and the control group. Plasma insulin dilution curve of tilapia was parallel to the insulin standard curve of human beings.