Blood samples are normally taken 12-14 hours after a fast because blood chemistry could be affected by recent food. Triglyceride, cholesterol, urea, electrolyte, and glucose values also may be altered if fasting has not occurred. The normal average values are for a healthy, non-athletic population. Athletes differ from the normal population in a number of ways. Athletes' diets are often lower in fat, so they have lower triglyceride and cholesterol values.
Athletes typically have higher red blood cell counts, hemoglobin readings, and hematocrits.
General Health Markers Glucose . The body uses glucose for energy. Urea is a waste product formed during the digestion of proteins and in urine is the vehicle for ridding the body of nitrogen. Blood urea is an indicator of kidney function. Creatinine also is a waste product formed during digestion.