The level of a chemical in urine may be expressed relative to creatinine. This can help to control for variation due to urine flow, patient hydration and other factors.
Steps:
(1) Determine the current units of measurement for the chemical of interest and for creatinine.
(2) Decide on the output units for expressing the ratio.
(3) Convert both the chemical and creatinine from the input units to mole per L.
(4) Convert the chemical and creatinine from mole per L to the output units per L.
(5) Divide the chemical output units per L by the creatinine output units per L, with the volume units canceling out.
concentration in mol/L =
= (value in original units) * (factor to convert to moles) * (factor to adjust to per liter)
concentration in output units per liter =
= (concentration in mol/L) * (factor to convert from moles)
number of grams of chemical =
= (number of moles) * (molecular weight in grams)
where:
• The molecular weight for the chemical needs to be known if converting between conventional and SI units.
• The molecular weight of creatinine: 113.1 grams
