Understanding the Effects of Exercise on Lab Tests
In order to get the most accurate readings from lab work, doctors often suggest things like “fast for twelve hours” or “don’t exercise for 48 hours” before going in for testing. Fasting requirements seem fairly logical, but why is it a bad idea to exercise?
Hydration & Blood Cells
Exercise alters the hydration levels of your cells. Both too much and too little fluid tend to show altered levels of red and white blood cells. (either too high or too low – both of which are red flags for serious conditions)
Blood/Protein in Urine
After exercise, urine often tests positive for blood or protein for 24-48 hours after. Doctors attribute it to the repetitive muscle breakdown of muscles during exercise that releases myoglobin. The muscle enzyme creatine kinase also is much higher after exercise. Recovery and hydration helps these levels return to normal over the next week.
Liver & AST
AST levels are significantly elevated after exercise. Measuring accurate levels of this enzyme is crucial in evaluating proper liver function.
Insulin & Blood Glucose Levels
During exercise, blood concentration of glucose decreases drastically to counteract the “insulin-like” effect of muscle contraction. More glucose is released from the liver during this time in order to fuel the muscles. Blood insulin levels drop, glucose and glucagon levels increase— resulting in potentially worrisome results on a blood test.