Excretion of creatinine in the urine can be used to estimate lean body mass. Since urinary creatinine excretion may vary from day, the average daily excretion over several days should be used. The authors are from the University of Rochester in New York.


(1) No dietary restrictions are required, although it probably should be fairly stable without wide swings in meat ingestion.

(2) The subjects ranged in age from 8 to 71 years. There were 21 males and 13 females.

(3) Timing of the urine collections need to be accurate. The urine specimens need to collected completely and stored at 4°C during the collection period.

(4) Urine is collected over 3 or more days and the average urinary creatinine excretion is calculated.


lean body mass in kilograms =

= (0.02908 * (urine creatinine in mg per day)) + 7.38



• The lean body mass is an approximation.

• Other methods are faster, cleaner and/or more accurate.

To read more or access our algorithms and calculators, please log in or register.