Question: We have a patient seen by our allergist that was given a promethazine injection, via intravenous (IV) line, for a total volume of 1 mL. The total duration for the order is 1 hour 53 minutes. What HCPCS code should I use for a 1 mL injection of promethazine? Arkansas Subscriber Answer: The HCPCS code you need to report an injection of the drug promethazine is J2550 (Injection, promethazine HCl, up to 50 mg). As you can see in the code description, you should report one unit of J2550 for up to 50 mg. The mL to mg ratio for J2550 is 1mL/25mg. Therefore, 1 mL of J2550 equates to 25 mg. Since the provider injected 1 mL of promethazine, you should accordingly only report one unit of J2550 for this service. You will report 1 unit for any injection equal to or below 2 mL.