(Brent S. Rushall)

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. Intense training may alter other parameters such as cortisol, AST, and CPK. Athletes typically have higher red blood cell counts, hemoglobin readings, and hematocrits.

1. Glucose. The body uses glucose for energy. Higher-than-normal blood glucose levels could indicate a disorder such as diabetes, in which glucose cannot be effectively removed from the bloodstream. Lower-than-normal blood glucose levels could indicate a disorder such as hypoglycemia, in which too much glucose is removed from the bloodstream.
2. Urea (Blood Urea Nitrogen). Urea is a waste product formed during the digestion of proteins and in urine is the vehicle for ridding the body of nitrogen. Proteins contain the element "nitrogen," which the human body cannot use. Blood urea is an indicator of kidney function. Athletes on a high protein diet may have higher-than-normal levels of urea in the bloodstream.
3. Creatinine. Creatinine also is a waste product formed during digestion. Normal levels in urine indicate the kidneys are effectively removing creatinine from the bloodstream.
4. Urea:Creatinine Ratio. Both urea and creatinine values are affected by diet as well as by other factors, so the best indicator of overall kidney function is the urea:creatinine ratio. Provided that the urea:creatinine ratio is within normal range, somewhat high or low values of either urea or creatinine are usually of no concern.
5. Cholesterol. Cholesterol is used to synthesize cell membranes, sex hormones, and some vitamins. When blood cholesterol levels are high, excess cholesterol may be deposited on the inner walls of blood vessels, which leads to the formation of atherosclerotic plaques. The National Cholesterol Education Program has determined a series of cholesterol classifications:

• Desirable (< 200 mg/dl); Borderline-High (200 - 239 mg/dl); and High (>240 mg/dl).
• Persons with blood cholesterol levels greater than 200 mg/dl risk developing coronary heart disease. Cholesterol levels are often genetically influenced; parents with high levels of cholesterol often having children with high levels of cholesterol. Cholesterol levels may be reduced by lowering the fat and cholesterol content in the diet and by exercising.
• Cholesterol molecules are referred to as "lipoproteins," with the total cholesterol measurement being the sum of low-density lipoproteins (LDLs) and high density lipoproteins (HDLs).
6. HDLs. HDL is the quantity of high-density lipoproteins (or cholesterol) in the bloodstream. HDLs are referred to as the "good" type of cholesterol. Their role is to transport excess cholesterol from the body to the liver, where it is removed from the bloodstream.
7. Cholesterol:HDL Ratio. The cholesterol:HDL ratio is a better indication of coronary risk than total cholesterol value. This ratio indicates how much of the total cholesterol reading is composed of HDLs. Higher levels of HDLs protect a person from cardiovascular disease, so the lower the cholesterol:HDL ratio, the less the risk of developing cardiovascular disease.
8. Triglycerides. A triglyceride is a fat. Triglycerides are found in foods and enter the bloodstream by way of the intestinal absorption. Triglycerides in the bloodstream may be deposited in either adipose or muscle tissue as body fat. High blood triglyceride readings indicate a diet is too high in fat. Blood triglyceride readings may be lowered by decreasing the percentage of total fat in the diet and by exercising.
9. Ferritin. Ferritin is the substance that recycles iron within the body. Iron, which is found in the red blood cell, binds to and transports oxygen within the body. The average life-span of a red blood cell in the human body is 90-120 days. If adequate quantities of ferritin are present, the iron molecule can be salvaged from the old red blood cell and incorporated into a new one. A low ferritin level is the first sign of anemia.

1. CPK (Creatine Phosphokinase). CPK is an enzyme found in muscle and the heart. During exercise, microscopic tears in the muscle allow CPK to leak into the bloodstream. These microscopic tears are normal and do not lead to injury, but they do allow CPK to enter the bloodstream. High intensity exercise leads to higher-than-normal CPK values in the bloodstream, so CPK values are typically higher than normal in athletes. CPK values may be used to evaluate an athlete's response to limited types of training stimuli.
2. AST (Aspartate Transaminase). AST is an enzyme found in the liver and muscle tissues. Physiological stress often leads to an elevation of AST. As well, elevated AST values may be a sign of liver or coronary damage.
3. Cortisol. Cortisol is a hormone secreted by the kidney in response to psychological or physiological stress. Cortisol increases the rate of breakdown of proteins, carbohydrates and fats. In times of stress, cortisol allows energy sources to mobilize to provide additional energy requirements. However, when cortisol levels are elevated over a prolonged period, the body can start to break down muscle in order to meet energy requirements.
4. LDH (Lactate Dehydrogenase). LDH is an enzyme found in the muscle, heart and liver. LDH levels may be elevated following intense exercise or in associated with liver or coronary disease.

1. Red Blood Cells. The red blood cell carries oxygen from the lungs to the tissues of the body. Low red blood cell counts indicate anemia. Anemia may lower the overall amount of oxygen that is delivered to working muscles. Anemia may be corrected by administering iron-rich foods or an oral iron supplement.
2. Hematocrit. Hematocrit is the percentage of blood that is composed of red blood cells. Low hematocrit readings also indicate anemia.
3. Hemoglobin. Hemoglobin is the actual substance that carries the oxygen within the red blood cell. Again, low hemoglobin readings indicate anemia.
4. White Blood Cells. White blood cells fight infection. Slightly high white blood cell counts indicate that the body is fighting an illness such as a cold or flu. Very high or very low white blood cell counts may indicate a more severe disorder.
5. Mean Corpuscular Volume (MCV). The MCV is the relative size of an individual red blood cell. Young red blood cells are larger than old red blood cells. Very high or very low MCV's may indicate disorder.

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