GPC (glycerophosphocholine) is a supportive nutrient for the brain, kidneys, muscles, testes and other organs, and is a building block for cell membrane phospholipids. Without the presence of this nutrient in the brain, we could not think, sleep or remember. The maintenance dosage of GPC is 300-600 mg per day, with a higher therapeutic dosage in the range of 600-1200 mg per day. The typical oral dose of GPC used in most trials is 1200 mg per day in divided doses, in order to maintain high blood levels throughout 24 hours.