Creatine is a nitrogen-containing compound found largely in skeletal muscle, where it functions as an energy source. Its use by muscles results in loss proportionate to the muscle mass and level of muscular activity. Measurement of serum creatine reflects this loss, which is fairly constant under normal conditions.

• Failure to follow dietary restrictions and vigorous exercise within 8 hours of the test may alter results.

• Signs and symptoms of muscular disease (e.g., muscle injury, muscular dystrophies, dermatomyositis), as indicated by elevated levels
• Monitoring for the progression of muscle-wasting diseases with serial measurements indicating the rate of muscle deterioration
• Evaluation of the effects of hyperthyroidism and rheumatoid arthritis on muscle tissue

Nursing Care Before the Procedure

Client preparation is essentially the same as that for any study involving the collection of a peripheral blood sample (see Appendix I).

• Food, fluids, and vigorous exercise are not permitted for at least 8 hours before the test.

A venipuncture is performed and the sample collected in a red-topped tube. The sample should be handled gently to avoid hemolysis and sent promptly to the laboratory.

Nursing Care After the Procedure

Care and assessment after the procedure are the same as for any test involving the collection of a peripheral blood sample.

• Resume foods and fluids withheld before the test, as well as usual activities.