Why Creatinine Levels Matter for Urine Drug Testing

August 18, 2023by Michael Miller2

Creatinine is an important component of urine drug testing. Tracking creatinine levels can enable treatment centers to fine-tune treatment plans and alert staff to clients who are trying to rig the system.

What is Creatinine and Why Does It Matter?

Creatinine is a waste product that is produced during muscle metabolism and is excreted through the kidneys. It is a reliable indicator of the body’s muscle mass and overall kidney function.

Because creatinine is produced at a relatively constant rate and is filtered by the kidneys, its concentration in urine should be consistent over time. This consistency makes creatinine an essential reference point in urine drug testing—and one on which Valley Medical Laboratory focuses.

Using Creatinine to Identify Urine Tampering

Measuring creatinine levels helps detect attempts to dilute or manipulate urine samples. Some individuals attempt to mask the presence of drugs in their system by consuming excessive amounts of water or other liquids before a urine test. This can lower the concentration of drugs and their metabolites in the urine, thus affecting the accuracy of the toxicology testing results.

What these individuals don’t realize, however, is that creatinine levels can help identify any attempts at urine dilution. That’s because diluting the urine in this fashion impacts the creatinine concentration. When a sample is diluted, the creatinine levels become abnormally low. When we find abnormally low levels of creatinine in a client’s urine, that suggests that the sample may have been tampered with, affecting the test results for other substances.

For these reasons, our reference lab compares the concentration of creatinine in each urine sample to typical ranges. If the creatinine level is within the expected range, it suggests that the sample is not diluted or tampered with, ensuring the accuracy of drug test results. If the creatinine level is not within range, providers are alerted and further testing may be necessary.

Other Factors That Might Contribute to Abnormal Creatinine Levels

Low creatinine levels are indicative but not determinative of urine tampering. There are several other factors that can contribute to unusual levels of creatinine in a person’s urine, including:

  • Kidney disease typically results in elevated creatinine levels
  • Muscle disorders can result in reduced creatinine production
  • Interaction with certain medications can influence creatinine production and excretion

Providers analyzing testing results need to take these medical considerations into account. Properly interpreting results requires skilled interpretation of the individual’s medical history and underlying health conditions.

Valley Medical Laboratory Standardizes Test Results to Creatinine Levels

At Valley Medical, we realize that creatinine is an integral component of urine drug testing, serving as a valuable indicator of sample integrity and dilution attempts. We go beyond simply measuring creatinine levels to standardizing all test results to the creatinine levels in the client’s urine.

By correlating creatinine levels with drug levels, our testing can accurately determine if the urine sample has been diluted. This identifies any attempt by clients to artificially dilute their samples to mask drug use.

Standardizing the client’s results for the amount of creatinine present provides a more accurate assessment of substances present in the client’s body. Most reference labs do not standardize to creatinine levels, which can potentially lead to misleading results and missed treatment opportunities.

This creatinine standardization is just one unique aspect of Valley Medical’s toxicology testing services. We also offer vTOX DNA verification that eliminates the need for viewed urine collection. For these and other reasons, treatment centers across the state of Minnesota rely on Valley Medical for fast, accurate, and easy to use toxicology testing.

Click here to learn more about vTOX urine drug testing at Valley Medical Laboratory—complete with DNA verification.


by Michael Miller

Michael Miller is a well-known writer with more than 200 books and thousands of articles published over the past two decades. His books have collectively sold more than 1.5 million copies worldwide.


  • Uly

    November 28, 2023 at 3:56 pm

    I don’t understand this testing method of testing your creatine levels.. My dr said my urine came out diluted like if I poured water in my urine and diluted it. I haven’t done any drugs for decades and I’m being accused of tampering with my drug test. Hows that?


    • Michael Miller

      November 28, 2023 at 4:25 pm

      We test creatinine levels on every urine sample as part of our validity testing. Low levels do not mean that urine has been tampered with necessarily, as there are several reasons a person could have low levels. It is ok to discuss this further with your provider to help explore a reasonable explanation for low levels if you know you haven’t tampered with your urine sample. If a provider questions you about your sample, that doesn’t mean you are being accused of tampering; instead, your provider is inquiring to see if one of those other reasonable explanations is likely.


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