Dietary supplement
According to US & Canadian Dietary Reference Intake guidelines, the protein Recommended Dietary Allowance (RDA) for adults is based on 0.8 grams protein per kilogram body weight. The recommendation is for sedentary and lightly active people. Scientific reviews can conclude that a high protein diet, when combined with exercise, will increase muscle mass and strength, or conclude the opposite. The International Olympic Committee recommends protein intake targets for both strength and endurance athletes at about 1.2-1.8 g/kg body mass per day. One review proposed a maximum daily protein intake of approximately 25% of energy requirements, i.e., approximately 2.0 to 2.5 g/kg.
Creatinine
The typical human reference ranges for serum creatinine are 0.5 to 1.0 mg/dL (about 45–90 μmol/L) for women and 0.7 to 1.2 mg/dL (60–110 μmol/L) for men. The significance of a single creatinine value must be interpreted in light of the patient's muscle mass. A patient with a greater muscle mass will have a higher creatinine level. While a baseline serum creatinine of 2.0 mg/dL (177 μmol/L) may indicate normal kidney function in a male body builder, a serum creatinine of 1.2 mg/dL (110 μmol/L) can indicate significant renal disease in an elderly female.