OPAT Billing Guide: How Infectious Disease Physicians Get Paid for Outpatient IV Antibiotic Therapy

OPAT billing is where infectious disease practices lose the most unpaid time. Physicians review weekly labs, adjust vancomycin doses and answer calls from home infusion nurses, yet much of that work never reaches a claim. One study of 1,064 OPAT courses found a median of 27 minutes of physician work per patient per week, or 40 minutes for patients on vancomycin.

This guide shows infectious disease physicians and their billing teams what can be billed for outpatient parenteral antimicrobial therapy (OPAT), who bills it in each setting, and how to document it so medical necessity and prior authorization denials stop.

Quick answer: OPAT billing depends on where the infusion happens. The infectious disease physician always bills the E/M visits, plus prolonged services when time supports it (99417 for most commercial payers, G2212 for Medicare). Infusion codes such as 96365 and the antibiotic J-code are billed only by the entity that gives the infusion. Non-visit oversight can sometimes be billed as care plan oversight, principal care management or an e-consult.

Where OPAT Happens and Who Bills What

OPAT billing starts with one question: who gives the infusion? The physician’s role stays the same in every setting, but the infusion and drug lines move to whoever administers them.

The Medicare Home Infusion Gap

Home OPAT is the hardest setting for home infusion therapy billing. The Medicare Part B home infusion benefit (G0068 to G0070 and G0088 to G0090) pays accredited suppliers only for drugs given through a covered DME pump. Its drug list includes IV antifungals and antivirals, but not antibiotics. As a result, most home IV antibiotics fall outside Part B, so the drug itself usually goes through the patient’s Part D plan instead. The Joe Fiandra Access to Home Infusion Act, signed in February 2026, changed the pump drug criteria but did not add IV anti-infectives.

E/M Visits and Prolonged Services: 99417 vs. G2212

Most OPAT billing income comes from office visits. Choose the level by medical decision making or by total time on the date of service, whichever supports more. OPAT visits often reach high-complexity MDM, because the physician manages drug toxicity that needs intensive lab monitoring.

When a visit is billed by time and runs past the highest level, add a prolonged services code. CPT 99417 and Medicare’s G2212 count time differently:

Watch out: Medicare treats 99417, 99358 and 99359 as not valid. A Medicare claim with 99417 will deny. G2212 also cannot be billed on the same date as 99415 or 99416, as Noridian’s prolonged service guidance explains.

For Medicare patients in a long OPAT course, consider G2211 as well. This add-on to 99202 to 99215 recognizes ongoing care for a single serious or complex condition. Since 2025, it is not payable when the visit carries modifier 25, except with a preventive service, vaccine administration or an annual wellness visit.

Billing the Work Between Visits

Lab review, dose changes and calls with infusion nurses happen between visits. This is the biggest gap in OPAT billing. Some of that work fits existing codes, but only when the conditions match:

• Care plan oversight (G0181 or G0182): 30 or more physician minutes in a calendar month for a patient under a Medicare home health or hospice episode. The physician must have signed the plan of care and seen the patient within the prior six months. Lab review counts toward the time.
• Principal care management (99424 to 99427): at least 30 minutes a month for one high-risk condition expected to last three months or more. Many OPAT courses last about five weeks, so confirm the condition, not just the antibiotic course, meets the three-month test.
• Interprofessional consults (99446 to 99449, 99451): when another clinician asks the ID physician for advice without a visit. 99451 needs at least 5 minutes, mostly data review, and a written report. The requesting clinician documents patient consent and may bill 99452.

Remote monitoring code 99091 rarely fits OPAT, because lab results are not patient-transmitted physiologic data.

Infusion CPT Codes 96365 and Add-Ons for OPAT Billing

When the practice gives the antibiotic in its own infusion suite, it bills the administration. Outpatient parenteral antimicrobial therapy coding follows the standard infusion rules:

• 96365: initial IV infusion, up to 1 hour. It must run more than 15 minutes; 15 minutes or less is a push.
• +96366: each additional hour of the same infusion, only when it runs more than 30 minutes past the hour.
• +96367: sequential infusion of a new drug, such as a second antibiotic after the first through the same access.
• +96368: concurrent infusion of two drugs at the same time.
• 96374 and +96375: IV push, initial and each new drug, used when the drug is pushed rather than infused.

Report only one initial infusion code per encounter unless a second IV site is medically necessary. Medicare contractors apply this rule to every infusion encounter.

In the office, the physician picks the initial code by the main reason for the encounter. Facilities follow a fixed hierarchy instead. Record start and stop times for every infusion, because time decides between 96365, 96366 and a push code.

Common OPAT Antibiotic J-Codes

• Vancomycin: J3373, per 10 mg (replaced J3370 on July 1, 2025).
• Ceftriaxone: J0696, per 250 mg.
• Daptomycin: J0878, per 1 mg.
• Dalbavancin: J0875, per 5 mg (1,500 mg = 300 units).
• Oritavancin: J2407, per 10 mg.

Confirm units against the current CMS HCPCS quarterly file before billing. Manufacturer-specific vancomycin codes J3374 and J3375 also exist.

Documentation for Lab Monitoring and Dose Changes

Strong documentation is the base of OPAT billing. It turns oversight work into billable, defensible claims. The 2018 IDSA OPAT guideline recommends an infectious disease expert review before OPAT starts and serial lab monitoring during therapy. Weekly labs are common practice, but follow your program’s protocol for each drug.

For each visit and each period of oversight, record:

• The infection, the organism and why IV therapy is still needed.
• Each lab result reviewed, such as CBC, creatinine and vancomycin levels, and what it means.
• Every dose change and the reason for it.
• Line care issues and adverse effects.
• Calls with the infusion pharmacy or home health nurse, with dates and minutes.
• Total time on the date of service when the visit is billed by time.

Use the same structure in every note, so a reviewer can follow the course week by week. Consistent notes also make it easier to support time-based visits, care plan oversight minutes and a prior authorization renewal when the course runs longer than planned.

IV Antibiotic Prior Authorization

IV antibiotic prior authorization usually comes from the patient’s plan, and many plans require it for specialty agents such as daptomycin or dalbavancin. Start the request before discharge, and include the culture results, the diagnosis and the planned duration. A missing approval is one of the fastest ways to lose OPAT billing revenue.

Do not count on the new federal clocks for the drug itself. Since January 1, 2026, CMS requires Medicare Advantage and Medicaid plans to decide most authorization requests within 72 hours (expedited) or 7 days (standard). That rule excludes drugs, however, including physician-administered Part B drugs. Our guide to electronic prior authorization under CMS rules explains what the rule does cover.

Top OPAT Billing Denials and How to Fix Them

• Medical necessity: the note does not show why IV therapy continues. Document the organism, response and lab trend at every visit.
• No authorization: the drug or setting changed without a new approval. Re-request when the drug, dose or site of care changes.
• Invalid code for Medicare: 99417 billed to Medicare. Bill G2212 at Medicare thresholds instead.
• Deleted code: vancomycin billed as J3370. Use J3373 per 10 mg.
• Bundled or duplicate administration: two initial infusion codes, or office codes billed for a hospital infusion. Report one initial code per encounter, and bill administration only where you gave it.
• Unsupported time: no total time or start and stop times. Record total minutes and infusion times.

When medical necessity denials still come back, our medical necessity denials guide covers how to appeal them.

The Bottom Line

OPAT billing pays fairly only when every billable piece is captured. Bill the visit at the level MDM or time supports, add G2212 or 99417 for the right payer, bill infusions only where you gave them, and capture eligible oversight between visits. Then back every claim with lab-driven notes.

Frequently Asked Questions