Serum creatinine is a laboratory test that is performed as part of routine blood work and to facilitate diagnosis of kidney disease, not supplement used to gain muscle. Low creatinine levels are a sign of reduced muscle mass, which may be caused by disease, debilitation or aging.
Facts About Low Creatinine
Creatinine is a breakdown product of creatine phosphate, which is used in the contraction of skeletal muscle. The production of creatine is dependent on muscle mass; therefore, baseline creatine and creatinine levels are higher in larger, more muscular people than in smaller people or those without much muscle.
Low Creatinine Levels and Kidney Health
Creatinine is excreted by the kidneys and its level in the blood is considered an indicator of kidney health. With normal kidney function, the blood creatinine level should be constant from day to day. Very minor increases can occur after a high-protein meal.
Causes of Abnormal Creatinine Levels
Increased blood creatinine is usually because of problems with kidney function. Increased breakdown of or injury to muscle will also raise the creatinine level, as will increases in muscle mass. Decreased blood creatinine is caused by decreased muscle mass.
Diseases Linked to Low Creatinine Levels
Low creatinine can be a sign of certain diseases which cause decreased muscle mass, including myasthenia gravis and muscular dystrophy. These patients will present with weakness, muscle wasting, and other symptoms in addition to the abnormal blood levels.
Debilitation and Low Creatinine Levels
Muscles atrophy when they are not used, and as the muscle mass decreases, creatinine levels will fall. This can happen with a debilitated patient, especially someone who has lost muscle tone from being bedridden or hospitalized.
Age and Low Creatinine
Elderly people may have a lower creatinine level, as the muscle mass tends to decrease with age. Young children also have a normal creatinine level that is lower than that of adults.