Our Blog

Understanding THC Levels in Urine Drug Screens

June 18th, 2019

NEW USE vs. NO USE of THC in urine drug screens:

Due to the increasing popularity of THC products such as waxes, sugars, and other potent concentrates, which typically range from 60-95% THC, frequent users may show positive results for upwards of 6-8 weeks. Understanding how to interpret UA results is key to determining whether your client is abstaining or continuing to use THC.
When looking at THC levels (Urine Drug Testing ONLY) to determine the pattern of use, it is important to consider the THC/ Creatinine Ratio and not the THC level alone. THC levels will fluctuate over the course of the day based on the clients’ hydration status. Morning urine is generally more concentrated than late afternoon urine, following the normal intake of daily fluids. In other words, the same client, testing at different times on the same day, would present with very different THC levels, even though the amount of THC in their system is generally the same.
The Ratio takes into consideration both the THC level and the Creatinine level and is calculated by simply dividing the two numbers. This number will be your BASELINE and will become the number by which you compare all future results to.
EXAMPLE: NO NEW/ DECREASED use of THC since baseline test on 5/17.
Test Date 5/17 5/24 5/29 6/6
THC Level 388 196 300 172
Creatinine Level 128.8 69.4 107.5 98.9
RATIO* 3.01* 2.82* 2.79* 1.74*

*RATIO = THC Level/ Creatinine Level

Results in which the Ratio continually decreases will show that the client has decreased and/or discontinued use of THC. In this example, despite the fluctuations in the THC levels, the decreasing THC/ Creatinine Ratio indicates that there has been decreased and/ or no new use of THC since the baseline test on 5/17.

EXAMPLE: NEW/ INCREASED/ SUSTAINED use of THC since baseline test on 3/22.

Test Date 3/22 4/11 4/17 5/13 5/24 6/3
THC Level 316 128 820 176 804 2052
Creatinine Level 40.8 47.3 123.6 38.0 67.4 262.6
RATIO* 7.25* 2.71* 6.63* 4.63* 11.93* 7.81*

*RATIO = THC Level/ Creatinine Level

*The fluctuating THC/ Creatinine Ratio between testing periods in this example shows evidence of decreased, increased and sustained use of THC. If the ratio on one test, is higher than the ratio on a previous test, this means that there has been new use of THC. Interesting to note: The THC levels on the 6/3 test are considerably higher than the 5/24 test, however, based on the ratio, there was decreased use between testing periods. This is reflected in the creatinine levels of 67.4, which is urine that is significantly less concentrated than that with a creatinine level of 262.6.
In summary, the THC Level ALONE is only an indication that there is still THC present in the system. It is the THC/Creatinine Ratio that is used to determine whether or not new use of THC has occurred.