nerphroll

Just something I was thinking about...

NFL Linebacker: 127.2 kg (280 lbs)
Lindsay Lohan 43.1 kg (95 lbs)
A very useful approximation for 24 hour urinary creatinine measurement is:
(Men)24 hr urine creatinine (mg) = 20 mg /kg body weight
(Women) 24 hr urine creatinine (mg) = 15 mg /kg body weight

Assuming they both have 24 hour urine volumes of 1300 ml:
the linebacker urine would have 2544mg creatinine / 1300 ml = 1.96 mg/ml
Lindsay lohan would have 647 mg creatinine / 1300 ml = 0.50 mg/ml

Now, the numerators in these equations, the total daily creatinine excreted, does not change day to day. Only the urine volume does, as a function of how much you drink. The more urine volume, the lower the concentration of creatinine in the urine. If you overdrink and dilute too much, the concentration falls below the detection threshold, and an alarm goes off to say “This is too dilute to say for sure it’s really human urine.”

Many tests require the urine creatinine concentration to be at least 15-20 mg/dl to be valid. Note these units are in mg/dl, not mg/ml. Converting from the concentrations above, we get:

Linebacker: 196 mg/dl
Lindsay: 50 mg/dL.

You get the idea. At baseline, your body build makes a big difference in your starting urinary creatinine concentrations (assuming equal urinary volumes in a day)

Now say they dilute. They each dilute like crazy. For the four hours before the test, they’re peeing like mad, each producing a volume of 2500 cc in that time. So into 2500 cc of urine would go 1/6th of their total daily creatinine production (since it’s a four hour block), so:
Linebacker pees 1/6th of 2544 mg = 424 mg creatinine
Lindsay pees 1/6th of 647 mg= 108 mg creatinine

Thus in that 2500 cc of urine, assuming it’s equal to the next time they void (which will be their testing sample), their final urine creatinine concentrations on their tests will be:

Linebacker: 0.169 mg/ml = 16.9 mg/dL =DILUTE if using 20 mg/dl test, VALID SAMPLE if using 15 mg/dl test

Lindsay: 0.050 mg/ml = 5 mg/dL = DILUTE, SAMPLE INVALID

POINT: The lower in muscle mass and overall weight you are, the easier it is for you to end up with a “diluted” sample if you use the dilution method. This example uses very idealized numbers, though everyone’s body is different. The urine volume of 2500 cc leading up to the testing may be excessive, but it is a worst case scenario. Realize that not diluting as much in order to get a valid sample makes it more likely for you to fail the test since the THC concentration will be slightly higher. As said before on these boards, a failed test is a failure, but a diluted one is simply invalid and does not incriminate you.