no adequate way to measure THC levels poor indicator no adequate way to measure THC levels dissolves in fat 5 nanograms NPR.org by the way isn’t yet an accurate test for impairment from marijuana use it fluctuates in people’s bloodstreams admits that NPR explains no adequate way to measure THC levels difficulty impaired driving from marijuana based on THC levels a poor indicator of current intoxication. blood and urine testing measured in the brain poor indicator isn’t yet an accurate test for impairment from marijuana use legalization of marijuana blood tests aren’t very accurate That doesn’t work so well either poor indicator it fluctuates in people’s bloodstreams too high to drive THC is fat-soluble that changes everything Shots has reported may not be accurate isn’t yet an accurate test for impairment from marijuana use