Oral creatine supplement use and urinary creatinine excretion

Measurement of creatinine in random urine specimens is performed routinely in urine drug testing programmes as an index of urine dilution. While using a creatinine cut-off of 25 mg/dL (2.2 mmol/L), 4.1% of 8,600 random urine specimens tested for drugs of abuse in this laboratory from 1997–98 were considered dilute. Recent media reports indicate that some elite athletes and bodybuilders consume the food supplement creatine as a natural muscle food. The objective of this study was to investigate whether the oral creatine product (SportsPep Creatine 1000™) would affect the urinary excretion of creatinine in five human subjects. Each subject collected baseline 24 h urine specimens. In study A, subjects consumed 3.0 grams of creatine orally at 0800h on days 1 and 2 with 24-h urine collections on day 2. In study B, subjects took 3.0 grams of creatine at 0800h for 5 consecutive days. On day 6, all subjects collected 24 h urine specimens for creatinine analysis. In study A, creatinine excretion (compared to baseline values) ranged from ↓17% to ↑51% (mean increase of 16%) above baseline values. In study B, creatinine excretion ranged from ↑11 to ↑196% (mean increase of 68%). Regular consumption of creatine products may limit the usefulness of creatinine analysis as an index of possible urine dilution in drug testing programmes.