HCPCS code S0136 – Clozapine 25 mg dispensing code

Key takeaways

HCPCS code S0136 reports clozapine in 25 mg units, so 100 mg a day for 30 days bills as 120 units.

S0136 carries Medicare coverage status I, not payable by Medicare, and no J-code stands in for it.

Medicare patients usually get oral clozapine through Part D, where the pharmacy bills the NDC.

The FDA ended the Clozapine REMS on June 13, 2025, but ANC monitoring continues under the prescribing information.

Pabau, the practice software we build, sends each claim from the patient record with supporting documents attached.

HCPCS code S0136 bills clozapine in 25 mg units

HCPCS code S0136 is a temporary national Level II code with the descriptor “Clozapine, 25 mg.” It took effect on April 1, 2003. Its Medicare coverage status is I, which means Medicare does not pay it.

The Centers for Medicare and Medicaid Services publishes the code set. S codes, though, exist for private insurers and Medicaid programs, which use them where no national code fits.

Clozapine treats schizophrenia that has not responded to other antipsychotics. It is also approved to reduce the risk of recurrent suicidal behavior in schizophrenia or schizoaffective disorder.

Because it is a later-line drug, payers often ask why it was chosen. On the claim, the diagnosis usually comes from the F20 schizophrenia family, such as F20.9, or from F25 for schizoaffective disorder.

S0136 covers the drug and leaves the monitoring separate

The code pays for clozapine itself, counted in 25 mg units. It does not bundle the services that surround a clozapine prescription.

Bill these separately, or write them off, according to each payer’s policy:

• Absolute neutrophil count (ANC) blood tests, billed under the lab’s own CPT codes
• Prescriber visits for titration, dose changes and monitoring
• Pharmacist dispensing fees, where a Medicaid program pays one separately
• Patient counseling on side effects and missed doses

Keeping those lines apart makes the claim easier to review. It also stops a payer from assuming the drug line includes services it never covered.

Medicare will not pay S0136, so sort payers at intake

Payer type decides whether S0136 belongs on the claim at all. The diagram below shows where each payer sends the drug, and the three questions after it are the ones billing teams ask first.

Does Medicare accept S0136?

No. CMS lists S0136 with coverage status I, so Medicare does not pay it, and most Medicare Advantage plans follow suit. No J-code substitutes for oral clozapine either. Medicare patients usually receive it through Part D, where the pharmacy bills the NDC on a pharmacy claim.

Does Medicaid accept S0136?

Often, but it varies by state. Many state programs process clozapine through the pharmacy benefit rather than the medical benefit. In that case, the pharmacy claim carries the drug instead of a HCPCS line. Confirm the billing channel with the state program before you file.

Do commercial plans accept S0136?

Many do, though prior authorization rules differ widely. Some plans also require step therapy records showing earlier antipsychotic trials. Check the plan’s drug policy before the first fill.

The Clozapine REMS ended in 2025, but ANC monitoring did not

The FDA eliminated the Clozapine REMS effective June 13, 2025. It had already stopped enforcing the program from February 24, 2025. Prescribers, pharmacies and patients no longer enroll, and pharmacies no longer need a REMS Dispense Authorization.

Severe neutropenia is still a risk, however. The Boxed Warning remains, and the FDA’s clozapine information points to the prescribing information for ANC monitoring. Prescribers still order baseline and ongoing ANC tests on that schedule.

For billing, the change is simple. A claim no longer depends on REMS enrollment or a dispense authorization. Some payers may still ask for a recent ANC in their prior authorization criteria, so keep results in the chart.

Units equal milligrams dispensed divided by 25

Each billed unit equals 25 mg of clozapine. To find the unit count, divide the total milligrams dispensed by 25.

Here is a worked example. A patient on 100 mg a day receives a 30-day supply. That is 3,000 mg in total, so the claim line shows 120 units. At 300 mg a day, the same supply bills as 360 units.

Under-reporting units is a common cause of underpayment on clozapine claims. Over-reporting, on the other hand, invites an audit. Record the milligrams on the dispensing note so anyone can recheck the math.

Most Medicaid and commercial payers want the National Drug Code on the line as well. Report it in the 11-digit 5-4-2 format, adding leading zeros where needed. The NDC on the claim should match the package dispensed.

Place of service affects routing too. A pharmacy uses POS 01, while an office that dispenses in-house uses POS 11. Some Medicaid programs restrict S0136 to pharmacy billing, so confirm the setting first.

Buy-and-bill is rare for an oral drug like clozapine

Under buy-and-bill, the practice buys clozapine from a wholesaler, dispenses it and bills the payer. Because clozapine is a tablet, most patients fill it at a pharmacy instead. Some integrated behavioral health programs and psychiatry practices still dispense it in-office.

If you do, keep the purchase invoice on file. Many Medicaid programs ask for acquisition cost records and may audit them against the billed amount.

How an S0136 claim moves from prescription to payment

A clean clozapine claim follows the same path every month. Here is how it usually moves, step by step.

1. Intake: Staff confirm the payer and flag the patient as Medicare or non-Medicare.
2. Authorization: Where the plan requires it, the team files prior authorization before the first fill.
3. Dispensing: The prescriber sets the dose, and the dispenser records milligrams and the NDC.
4. Claim build: The biller converts milligrams to units, adds the NDC and links the F20 or F25 diagnosis.
5. Submission: The claim goes to the payer or clearinghouse with any supporting documents attached.
6. Remittance: The team posts payment from the ERA, or works the denial within the payer’s deadline.

Most problems start at steps 1 and 4. A Medicare patient billed under S0136 fails at once. So does a unit count built from days supplied rather than milligrams.

Speed matters here for a clinical reason, too. If a patient misses clozapine for two days or more, the prescribing information calls for re-titration from a low dose. A stalled refill can set the patient’s treatment back.

Prior authorization turns on diagnosis and treatment history

Many commercial plans and state Medicaid programs require prior authorization for S0136. Criteria vary, but most requests draw on the same core records.

• Diagnosis: An F20 or F25 code, with chart notes describing treatment resistance or suicidal-behavior risk
• Treatment history: Records of earlier antipsychotic trials, in the number and form the payer’s policy sets. Some plans ask for at least two failed trials.
• Lab results: A recent ANC, where the payer’s criteria ask for one
• Prescriber details: The ordering prescriber’s NPI and the planned dose

Turnaround depends on the plan and on whether the request is marked urgent. Track each approval’s end date, because a lapsed authorization denies the next claim. If a plan refuses the request, ask about peer-to-peer review and lead with the clinical rationale.

Reimbursement for S0136 depends on each payer’s rate

S0136 has no Medicare fee schedule amount, because Medicare does not pay it. Instead, each Medicaid program and commercial contract sets its own rate.

State Medicaid programs usually price oral drugs against a benchmark, such as acquisition cost plus a dispensing fee. Check the current rate with your state agency, or use the PGM Billing HCPCS lookup tool as a starting point.

Commercial rates are contract-specific, and out-of-network claims often pay usual and customary amounts. Confirm the allowed amount against the ERA from your most recent paid claim.

Common errors that trip up S0136 claims

Clozapine claims deny for predictable reasons, and most are fixable upstream. Good denial management in healthcare starts by matching each error to its adjustment code. Then you fix the step that caused it.

A missing or misformatted NDC is a common cause of Medicaid denials on this code. A quick NDC check at dispensing prevents many of them.

Documentation that holds up when a payer audits S0136

A paid claim can still be recouped after an audit. The chart and the dispensing record should show these items.

• Diagnosis: An F20 or F25 code documented by the prescriber, not inferred from the prescription
• Treatment history: Notes or pharmacy records showing earlier antipsychotics, doses, duration and why each stopped
• ANC results: Recent values and collection dates, in line with the prescribing information schedule
• Quantity in milligrams: The exact amount dispensed, so an auditor can recheck the unit count
• NDC: The code from the package dispensed, recorded at the time, rather than a default from a drug database
• Authorization: The approval number and dates, where the plan required one

Linking the clinical record, the dispensing note and the claim surfaces missing items sooner. Treating medical billing as part of the clinical workflow makes that link routine. For what auditors expect to see, read our medical billing compliance guide.

Check these items before you submit an S0136 claim

Run this list before each claim leaves the practice. It takes a minute, and a claim that passes all seven checks stands the best chance of paying as a clean claim.

• The patient is non-Medicare, or the fill has gone to Part D.
• Units equal total milligrams divided by 25.
• The 11-digit NDC matches the package dispensed.
• An F20 or F25 diagnosis is linked to the drug line.
• Prior authorization is on file and still in date.
• A recent ANC result sits in the chart.
• Place of service matches the payer’s rules for pharmacy or office billing.

How Pabau keeps clozapine claims moving

Many psychiatric practices split clozapine billing across a chart, a pharmacy note and a separate billing tool. Each handoff is a chance to lose the NDC, the unit count or the authorization number.

Pabau, the practice management platform we build, keeps the patient record and the claim in one place. Its claims management builds each claim from the patient’s invoice, and US practices submit through Claim.MD.

Before you send, you can attach supporting documents to the claim. That means fewer handoffs between clinical and billing staff, and a clearer trail when a payer asks questions.

Send psychiatric claims from one record

Pabau builds claims from the patient’s invoice and sends them with supporting documents attached. Your team spends less time passing paperwork between clinical and billing staff.

Book a demo

Conclusion

Treat S0136 as a non-Medicare code from the first conversation with the patient. Once the payer route is settled, the rest is arithmetic and records. That means milligrams over 25, a matching NDC and a linked diagnosis.

With the REMS gone, attention shifts to prior authorization and audit-ready charts. Keep ANC results filed on schedule, because clinicians and payers still look for them.

If clozapine billing still runs across separate systems, closing those handoffs is the next step. Book a demo to see how Pabau sends psychiatric claims with the right documents attached.

Continue your research

Want fewer clozapine denials? Denial management in healthcare shows how to build checks into billing before claims go out.

Comparing claims tools for psychiatric billing? Claims management software explains how Pabau builds and submits claims from the patient record.

Coding the diagnosis line? ICD-10 code F20.9 explains how to report unspecified schizophrenia on a claim.

Preparing for a billing audit? Medical billing compliance covers what auditors check and how to document it.

Frequently asked questions