HCPCS code S0091 – Granisetron hydrochloride, 1 mg

Key takeaways

HCPCS Code S0091 reports granisetron hydrochloride, 1 mg, an antiemetic drug. One unit equals 1 mg.

S0091 is a temporary national S code for private payers and some Medicaid programs. Medicare does not pay it.

For Medicare, bill Q0166 for oral granisetron given with chemotherapy, or J1626 for the injection, billed per 100 mcg.

Pabau, the practice software we build, sends US claims through Claim.MD and posts the remittance against the patient record.

HCPCS Code S0091: Definition and code description

HCPCS Code S0091 is the HCPCS Level II code for granisetron hydrochloride, 1 mg. Granisetron is an antiemetic that prevents the nausea and vomiting caused by chemotherapy and radiation. One unit of S0091 equals 1 mg, so a 2 mg dose is billed as two units.

The full official descriptor reads: “Granisetron hydrochloride, 1 mg (for circumstances falling under the Medicare statute, use Q0166).” The note in brackets is part of the code. It tells you that S0091 is the non-Medicare version, and that Medicare claims take a different code.

S0091 belongs to the S code range of temporary national codes. CMS publishes these codes in its HCPCS files, but it does not create them. The Blue Cross Blue Shield Association and AHIP (formerly the Health Insurance Association of America) request them for private-sector use.

Private insurers use S codes for drugs, supplies and services that no permanent national code describes the way they need. State Medicaid programs may use them too. The range covers oral drugs as well, such as tacrine hydrochloride, 10 mg, under S0014.

Medicare does not pay them, and the CMS file gives S0091 coverage code “I”, which means not payable by Medicare. Oral dolasetron follows the same split, with S0174 for private payers and Q0180 for Medicare.

S0091 code details at a glance

The table below summarizes the reference data for HCPCS Code S0091 in the October 2026 CMS HCPCS Level II file.

What granisetron is used for

Granisetron blocks serotonin 5-HT3 receptors, which trigger the vomiting reflex after chemotherapy or radiation. The FDA label for granisetron hydrochloride 1 mg tablets covers two uses. The first is preventing nausea and vomiting from initial and repeat courses of emetogenic cancer therapy, including high-dose cisplatin.

The second is nausea and vomiting from radiation, including total body irradiation and fractionated abdominal radiation. The usual adult oral dose for either use is 2 mg a day. That is two 1 mg tablets once daily, or 1 mg twice daily for chemotherapy.

That dosing is why units matter on an S0091 line. A 2 mg dose is two units, and a 1 mg twice-daily regimen over a day is also two units. Granisetron also comes as an injection, an extended-release injection and a skin patch, and each of those has its own coding rules.

S0091 vs Q0166 vs J1626: Which granisetron code to bill

The right granisetron code depends on two things: who pays the claim, and how the drug was given. S0091 is the code for non-Medicare payers that accept it. Q0166 and J1626 are the Medicare codes.

Q0166 is narrower than it looks. Its descriptor limits it to an oral antiemetic used as a complete therapeutic substitute for an IV antiemetic at the time of chemotherapy.

It is capped at a 24-hour dosage regimen. A prescription for oral granisetron filled for use at home is usually a Part D pharmacy claim instead.

J1626 counts in 100 mcg units, so a 1 mg IV dose is 10 units of J1626 but one unit of S0091. Mixing the two unit sizes is the fastest way to underbill or overbill granisetron. Extended-release granisetron injection has its own code, J1627, billed per 0.1 mg.

The chart below runs those rules in the order a biller meets them: payer first, then route.

Which payers accept HCPCS Code S0091?

Private insurers and some state Medicaid programs accept HCPCS Code S0091, and Medicare never does. Each payer decides for itself whether to recognize an S code, so acceptance varies plan by plan.

Knowing how medical billing works across payer types explains why one code can be valid on one claim and rejected on the next.

• Medicare: S codes are not payable by Medicare, and they may not be billed under any Medicare payment system. Use Q0166 for oral granisetron given with chemotherapy, or J1626 for the injection.
• Medicaid: some state programs list S0091 on their fee schedules and others do not. Check the state’s HCPCS fee schedule or provider manual before you bill it.
• Commercial insurers: many Blue Cross Blue Shield plans and other private payers recognize S codes, but not every plan covers S0091. Some may want J1626 for an injected dose, or may cover oral granisetron only through the pharmacy benefit.
• Medicaid managed care plans: these usually follow the state’s code list, but a plan contract can differ. Confirm with the plan, not only the state.

How to report units and the NDC for S0091

Report units of S0091 as total milligrams given, because one unit equals 1 mg. A clean drug line needs five details to agree with each other.

1. Units: enter total milligrams. A 2 mg dose is two units, never one.
2. NDC: report the 11-digit National Drug Code from the package, with the N4 qualifier, when the payer asks for it. State Medicaid programs collect NDCs on drug claims for federal rebates, so most require one.
3. NDC quantity: enter the quantity in the NDC unit of measure, such as UN for each tablet. This is separate from the HCPCS units.
4. Date of service: use the date the dose was given or dispensed, matching the chemotherapy or radiation record.
5. Diagnosis pointer: link the line to the nausea or vomiting diagnosis and to the cancer treatment encounter.

An S0091 line with one unit for a 2 mg dose underpays by half. A line with 20 units, copied from a J1626 habit, will be denied or flagged for review.

ICD-10-CM codes to pair with S0091

Pair S0091 with a diagnosis that shows why the antiemetic was needed and what treatment it supported. When the nausea is an adverse effect of chemotherapy, ICD-10-CM guidelines put the nature of the effect first. The drug that caused it comes second.

Add the code for the cancer being treated as well, since most payer policies tie antiemetic coverage to an active cancer treatment. Each payer’s drug policy sets the diagnoses it accepts, so check it before you rely on a pairing.

Documentation requirements for S0091 claims

The medical record has to support the drug, the dose and the reason for it. Good medical billing compliance for an S0091 claim means the chart shows each of these.

• The order: a signed order for granisetron, with dose, route and frequency
• The dose given: the milligrams given or dispensed, which must match the units billed
• Timing: the date and time of the dose relative to chemotherapy or radiation
• Indication: the treatment it supports and the emetic risk that justified it
• Drug details: the NDC, lot number and route for a dose given in the practice
• Authorization: the prior authorization number, where the payer requires one

Common billing errors and claim denials

Most S0091 denials come from billing the wrong payer, the wrong unit count or an unsupported diagnosis. Strong denial management treats each one as a check before submission.

The CARC tells you which rule the payer applied, and the remark code that comes with it narrows the reason further. Our guide to denial codes in medical billing explains how to read both before you correct or appeal the claim.

How Pabau supports antiemetic drug billing

An antiemetic claim touches three records: the chemotherapy schedule, the drug administration note and the claim itself. When they live in separate systems, billing staff re-type the dose and the NDC by hand. That is where unit errors and wrong-payer codes come from.

Pabau keeps the patient record, the clinical notes and the claim in one place. The dose on the administration note is the dose that reaches the claim.

Its claims management software sends US claims through the Claim.MD clearinghouse. It also runs eligibility checks, so the team knows the primary payer before choosing between S0091, Q0166 and J1626.

Electronic remittances post back against the same patient record. A practice can see which payers paid S0091 and which wanted J1626, then submit clean claims from the first attempt next time.

Bill the right granisetron code for every payer

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Conclusion

S0091 is a simple code with one trap built into its own descriptor. It bills granisetron at 1 mg per unit, and only for payers outside Medicare. The bracketed note sends Medicare claims to Q0166, and an injected dose usually belongs on J1626 at 100 mcg per unit.

Get the payer right first, and the code and unit count follow from it. Book a demo to see how Pabau keeps eligibility, drug records and claims in one workflow.

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