While exercise doesn't eliminate protein in the kidneys, very vigorous exercise might cause proteins in the blood to pass into the urine via the kidneys. While small amounts of protein in the urine are fairly normal, this should not be confused with proteinuria. Proteinuria involves sustained levels of protein in the urine that are abnormally high.
Kidneys
The kidneys filter the blood and remove waste products. These waste products are usually nitrogenous compounds, such as creatinine and urea, that occur naturally as proteins break down. Healthy kidneys keep protein in the blood and prevent it from spilling into the urine. Normal urine specimens have very little protein in them.
Normal Values
One common way to measure urine protein is calculating the ratio of protein to creatinine in a urine specimen. For the patient, this test involves no more than delivering a urine specimen to your health care provider so he can perform a urinalysis. The normal ratio for adults and children over age 2 is 0.2 g protein per gram of creatinine.
Abnormal Values
Your protein-to-creatinine ratio might be slightly high if you have been exercising vigorously just prior to providing the specimen. If your urine contains slightly more protein than normal, your doctor will probably order that the test be repeated. This slight elevation should not be confused with the high urine protein values that accompany kidney disease.
Kidney Disease
High urine protein is a red flag for kidney disease. Although some patients experience puffy eyes and swollen feet, others experience no symptoms at all, especially if their urine protein levels are under 3.0 g protein per gram of creatinine. If the follow-up urinalysis shows high urine protein, then blood work, an ultrasound and kidney biopsy may be required.
