The quantity denominator built into a HCPCS drug code, which converts an administered dose into the number reported on the claim.
The descriptor states it: injection, pembrolizumab, 1 mg means one unit equals one milligram. Injection, infliximab, 10 mg means a 400 mg dose is 40 units.
Units are the single largest source of drug-claim overpayment and underpayment. A code whose unit is 10 mg, billed as though it were 1 mg, overstates the claim tenfold and is a standard audit target.