The influence of the plant growth regulator gibberellic acid (GA(3)) on the hemolymph contents of Galleria mellonella (Lepidoptera: Pyralidae) was examined. G. mellonella larvae were fed with a synthetic diet. The effects of GA(3) on the hemolymph content of these larvae were tested through a diet incorporation assay. Different concentrations (2, 5, 10, 50, 100, 200, 500 and 1000 mg/L) of GA(3) were added to the synthetic diet and protein, lipid, carbohydrate and glycogen levels in the hemolymph were evaluated for the GA(3) concentrations. The hemolymph protein level of the larvae increased significantly at 5, 10, 50 and 200 mg/L with respect to the control group. The lipid level of hemolymph fluctuated among the tested GA(3) concentrations. It was significantly reduced at 5 and 10 mg/L, but increased at 50 and 200 mg/L. GA(3) application also enhanced the carbohydrate level at 50, 100, 200 and 1000 mg/L and the glycogen content at 100 and 200 mg/L.