A method for determining a person's metabolic typing. The method includes the steps of taking a baseline reading to determine a person's blood pH, administering a substance challenge to a person to determine how the substance affects the person's blood pH, waiting a period of time, retaking the person's blood ph, and from any difference in the baseline reading and post-challenge reading, determining if the patient's blood has been alkalized or acidified by the substance challenge in order to determine the person's metabolic type. The invention is also a method to test the blood pH shifting effects of substances on people of different metabolic types, by determining whether the substance will cause the blood of persons having known metabolic types to become more acidic or alkaline.