D/L methamphetamine,urine

We do methamphetamine testing in house, but if a D/L amphetamine is requested due to a positive methamphetamine we send this test to an outside lab if requested. To bill for this service for commercial payers we use 80374, however I am unsure as to the code to use for Medicare. Any guidance or experience in this area is greatly appreciated. Thanks

D/L methamphetamine,urine