Topics: Gastric function tests, Caffeine Stimulation, gastric stimulation, intestinal function tests, digestion absorption, malabsorption, glomerular filtration rate, Creatinine clearance, insulin clearance, concentration test, dilution tests, urinary acidification test, urine specific gravity, urinary osmolarity, dye excretion test, water status electrolyte status, blood buffers, lipids, ketone bodies, plasm proteins, carbohydrate metabolism, Blood glucose homeostasis, Hyperglycemia, diabetes mellitus, Hypoglycemia