MMA can be measured in blood, but can also be measured in the urine, as long as we take into account how well the kidneys are working. We do this by measuring a substance called creatinine that is filtered into the urine by the kidneys. When we compare the urinary MMA to urinary creatinine, it improves the accuracy of the MMA test in urine when compared to blood, because it is not affected by mild to moderate decrease in kidney function.
