Creatinine is a metabolic by-product of muscle metabolism, and normally appears in urine in relatively constant quantities over a 24 hour period with normal liquid intake. Therefore, urine creatinine can be used as an indicator of urine water content or as a marker identifying a specimen as 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.