Creatinine

The revised levels at which creatinine may be considered dilute (<20 ml/dL) or abnormally dilute (<=5 mg/dL) are based on the critical points that SAMSHA has set as decision points for interpreting dilute or substituted urine specimens.

General

Creatinine is a metabolic byproduct of protein metabolism, which normally appears in urine in relatively constant quantities over a 24-hour period with regular liquid consumption. Therefore, urine creatinine can be used as an indicator of urine water content or as a marker value for urine. Greater than normal intake of water will increase the urine water content (lowering the creatinine level) consequently diluting the amount of drug in urine. Conversely, a limited intake of water can lead to an abnormally concentrated urine specimen (as occurs with dehydration) resulting in elevated creatinine levels.

< 20 mg/dL

Dilute urine specimen - most likely due to increased water intake. Can be a result of short-term water loading (flushing) in an attempt to dilute any drug below testing cutoff concentrations.

<=5 mg/dL

Abnormally dilute - specimen showing an excessively low creatinine value. May be indication that the specimen is not consistent with normal human urine.

Note: The above interpretations are general guidelines. RTL recommends consulting with a toxicologist regarding proper interpretation prior to taking administrative action based solely on the creatinine concentrations. Other physiological conditions may account for low creatinine concentrations such as diabetes or use of prescription diuretics.