CPT code 91065: Hydrogen breath test billing guide

Key Takeaways

CPT code 91065 describes the breath hydrogen or methane test, used to detect lactase deficiency, fructose intolerance, bacterial overgrowth, or oro-cecal gastrointestinal transit.

Payers including Medicare follow CMS NCD 100.5 for coverage of CPT 91065, which excludes lactulose-based SIBO and transit-time testing; prior-authorization requirements vary by payer and change over time, so always confirm against the current policy before scheduling.

SIBO protocols often support 2 units of CPT 91065 per session when both hydrogen and methane are measured separately, but unit count must be confirmed with each payer before submission.

Pabau’s claims management software helps gastroenterology and primary care practices track CPT 91065 submissions, flag payer-specific rules, and reduce claim denials.

CPT code 91065: Definition, clinical use, and billing overview

The 91065 CPT code description, according to the American Medical Association (AMA), reads: Breath hydrogen or methane test (eg, for detection of lactase deficiency, fructose intolerance, bacterial overgrowth, or oro-cecal gastrointestinal transit). The 91065 CPT code falls under the Gastroenterology section of the CPT code set, within the range covering esophageal balloon distension studies and breath tests.

Breath testing claims are among the most frequently miscoded in gastroenterology. Incorrect unit counts and unsupported ICD-10 pairings drive a disproportionate share of denials. The same billing discipline applies to other high-volume codes. J3357, for example, carries similar audit exposure when units or modifiers are mismatched.

This guide covers the official descriptor, clinical indications, documentation requirements, modifiers, Medicare and payer policies, companion codes, and ICD-10 pairings for CPT 91065. It is written for coders, billing specialists, and clinical staff in gastroenterology and primary care practices.

What does CPT code 91065 measure?

The breath hydrogen or methane test works on a straightforward physiological principle. When carbohydrates are not absorbed in the small intestine, they ferment in the gut. That fermentation produces hydrogen (H2) and methane (CH4), which are absorbed into the bloodstream, transported to the lungs, and exhaled in measurable concentrations.

CPT 91065 captures any breath test that measures H2 or CH4, or both, making it the single code for several distinct clinical questions. The substrate used (lactulose or glucose) and the timing of sample collection vary by protocol, but the code itself does not change based on substrate choice.

That is why the lactose breath test CPT code, the lactulose breath test CPT code, and the fructose breath test CPT code are all the same: 91065. Only the substrate and sampling schedule change, not the code you bill.

CPT 91065 applies to five primary clinical scenarios:

• Small Intestinal Bacterial Overgrowth (SIBO): Excess bacteria in the small bowel ferment ingested substrate early, producing a premature hydrogen or methane rise.
• Intestinal Methanogenic Overgrowth (IMO): Methane-dominant patterns now classified separately under the 2020 ACG (American College of Gastroenterology) Clinical Guideline on SIBO; associated with constipation-predominant symptoms.
• Lactase deficiency / lactose intolerance: Unabsorbed lactose reaches the colon and ferments, producing a late hydrogen rise.
• Fructose intolerance / malabsorption: Excess fructose that bypasses absorption triggers fermentation and elevated exhaled hydrogen.
• Oro-cecal gastrointestinal transit: Measuring the time from ingestion to first colonic fermentation as a proxy for small bowel transit time.

Medicare coverage differs sharply across these scenarios. Lactose breath hydrogen testing for lactase deficiency is a covered indication under CMS NCD 100.5, while lactulose-based SIBO, IMO, and oro-cecal transit testing are explicitly excluded from coverage.

A standard 2-hour SIBO protocol collects six fasting breath samples: at baseline, 20, 40, 60, 90, and 120 minutes. Three-hour protocols extend sampling to 180 minutes and are used when a longer transit time is suspected. Practices integrating EHR workflows with laboratory ordering can automate result routing and reduce documentation lag.

CPT code 91065 billing guidelines and units

One of the most common billing questions for CPT 91065 is how many units can be submitted per session. The short answer: it depends on the payer.

Commonwealth Diagnostics International and FoodMarble Healthcare both reference CPT 91065 billed as 2 units for SIBO testing protocols that measure both hydrogen and methane as separate analytes. The rationale is that H2 and CH4 represent two distinct gas measurements, each clinically meaningful on its own.

However, not all payers accept 2 units. Many process CPT 91065 as a single unit regardless of how many gases are measured. Before submitting CPT code 91065 x2 (two units), verify the payer’s specific policy. Billing 91065 x2 without payer authorization is a common audit trigger.

Modifiers for CPT 91065

Modifier 59 (Distinct Procedural Service) is the most common modifier applied to CPT 91065 when multiple breath tests are performed on the same date of service. It signals to the payer that the services are separate and distinct, not duplicates.

The more specific X-modifiers (XE for separate encounter, XS for separate structure, XP for separate practitioner, XU for unusual non-overlapping service) can be used in place of modifier 59 when the clinical distinction is more granular.

Modifier 26 (Professional Component) may apply when a physician interprets the results of a test performed by a reference laboratory. Modifier TC (Technical Component) applies when a facility performs the test but a separate physician reads the results.

These are less common for 91065 but relevant for hospital outpatient or lab-based billing. Practice management platforms with time-saving features can automate modifier flagging within billing workflows.

Repeat-procedure modifiers come up occasionally but rarely apply to CPT 91065. Modifier 76 marks a repeat test by the same physician, modifier 77 a repeat by a different physician, and modifier 91 a repeated clinical laboratory test on the same day.

Because breath tests are normally ordered on separate days, append these only when a same-day repeat is genuinely necessary and documented.

Medicare coverage and payer policies for CPT code 91065

Medicare coverage of CPT 91065 is governed by CMS National Coverage Determination (NCD) 100.5, Diagnostic Breath Analyses. Under this NCD, the Centers for Medicare and Medicaid Services (CMS) addresses coverage criteria for exhaled breath testing.

Use the CMS fee schedule lookup to confirm current reimbursement rates by geography and setting, since Medicare rates differ between facility and non-facility settings and are updated annually.

Coders often ask whether Medicare covers the SIBO breath test. NCD 100.5 explicitly excludes lactulose breath hydrogen testing for diagnosing small bowel bacterial overgrowth, and for measuring small bowel transit time, from coverage. Only lactose breath hydrogen testing to detect lactose malabsorption is a covered indication.

That means a lactulose-based SIBO protocol and a lactulose-based oro-cecal transit study are both excluded from Medicare coverage outright. Check the indication and substrate against your Medicare Administrative Contractor’s (MAC) local coverage determination before scheduling, rather than assuming either workup is reimbursed.

Prior-authorization requirements vary by payer and shift over time, so don’t assume a policy you checked previously still applies.

Providence Health Plan’s current Medicare Medical Policy #29 (“Exhaled Breath Tests,” effective February 1, 2026) ties CPT 91065 coverage to CMS NCD 100.5 and no longer lists a separate prior-authorization requirement for the code, though an earlier 2021 version of that policy did require it. Always check the specific plan’s current prior-authorization list before ordering the test.

Moda Health’s Hydrogen Breath Testing policy (CWQI HCS-0250) covers CPT 91065 only for lactose intolerance and lactase deficiency, alongside companion code CPT 82542 (quantitative column chromatography).

Moda explicitly classifies the test as experimental and investigational, and therefore not covered, for SIBO, IBS, and small-bowel transit or gastroparesis workups, so don’t assume a Moda policy that covers 91065 for lactose testing also covers a SIBO-indication order.

EmblemHealth’s reimbursement policies also reference CPT 91065 in the context of diagnostic testing coverage. State Medicaid coverage varies; New York Medicaid’s physician procedure codes manual has listed CPT 91065, though currency of that listing should always be verified against the current eMedNY manual. Tracking these payer-specific rules is where claims management software delivers measurable time savings for billing teams.

Reimbursement rates for CPT 91065

Medicare reimbursement for CPT 91065 typically ranges from about $60 to $130 depending on locality, geographic practice expense adjustments, and the care setting. Commercial payer rates vary significantly and are not published uniformly.

Use the FastRVU RVU lookup tool to pull current Work, Practice Expense, and Malpractice RVU values for CPT 91065 and calculate the conversion factor for your locality. Rates change with each CMS annual update; always cite the applicable fee schedule year in your documentation.

Documentation requirements for CPT code 91065

Thorough documentation is the single biggest factor in avoiding denials and surviving audits for CPT 91065. Payers want to see medical necessity established before the test, not reconstructed after a denial. Use digital intake forms to collect and store all pre-test information in a structured, retrievable format.

Minimum documentation requirements for a billable CPT 91065 encounter include:

• Ordering physician’s clinical note: Document the presenting symptoms (bloating, diarrhea, abdominal pain, constipation), duration, and prior workup that justifies breath testing over other diagnostic options.
• Diagnosis supporting medical necessity: The ICD-10 code on the claim must match the clinical picture. Use a specific code where possible rather than a symptom-level code.
• Test protocol documented: Record which substrate was used (lactulose or glucose), the duration of the test (2-hour or 3-hour), and the number of samples collected with timestamps.
• Gas measurements at each time point: Baseline, 20-minute, 40-minute, 60-minute, 90-minute, and 120-minute (or up to 180-minute for 3-hour protocols) readings for H2 and CH4 in parts per million (ppm).
• Physician interpretation: A signed interpretation note stating whether results are positive, negative, or indeterminate, and the clinical significance.
• Patient preparation compliance: Note that the patient followed the required prep, which typically means a 12-hour fast, no antibiotics for about four weeks, no laxatives or fiber supplements for one week, and no smoking for 24 hours before the test. Failed preparation can invalidate the test and the claim.

Practices following HIPAA-compliant documentation practices should store breath test results, interpretation notes, and authorization records within the patient’s electronic record, accessible for audits. Medical forms at practices have shifted toward digitized structured fields that keep billing documentation complete.

Reduce CPT 91065 claim denials with smarter billing workflows

Pabau helps gastroenterology and primary care practices track breath test submissions, manage payer-specific rules, and keep documentation audit-ready, so your team spends less time on rework and more time on patient care.

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ICD-10 codes paired with CPT code 91065

Selecting the right ICD-10 code is as important as selecting CPT 91065 itself. The diagnosis code establishes medical necessity. Use the AAPC CPT-to-ICD-10 crosswalk to identify payer-accepted diagnosis codes for this procedure. The most commonly paired codes are:

Use the most specific ICD-10 code available. Symptom-level codes (R14.0, R14.3) are acceptable when a confirmed diagnosis has not yet been established, but payers may require a more specific code for prior authorization approval.

Functional medicine and integrative practices ordering SIBO breath tests frequently pair K58 and K59 series codes with CPT 91065; those practices benefit from functional medicine software that supports structured diagnosis coding alongside lab ordering.

Companion codes and combinations for CPT 91065

CPT 91065 is sometimes submitted alongside other codes depending on the clinical workflow. Several companion codes appear in payer policy documents:

• CPT 82542 (Column chromatography, qualitative/quantitative): Moda Health lists this as a companion code to CPT 91065. Some labs use chromatography-based analysis for gas measurement. Before adding CPT 82542, verify NCCI (National Correct Coding Initiative) bundling rules; some payers bundle it into 91065 and will deny a separate line.
• CPT 83987 (pH; exhaled breath condensate): Providence Health Plan lists CPT 83987 as “not covered” on the same policy that covers 91065. These are distinct procedures; do not conflate or submit together without confirming payer acceptance.
• CPT 0106U (Gastric emptying breath test, proprietary): A proprietary laboratory analysis code for a specific commercial breath test. This is separate from CPT 91065 and cannot be substituted for it.

When a practice bills both CPT 91065 and an evaluation and management (E&M) code on the same day, the E&M must reflect a separately identifiable medical decision-making process beyond ordering the breath test.

Append modifier 25 to the E&M code, commonly 99211, to prevent bundling. Practices using practice management software features that support modifier logic can automate these checks before claim submission.

IMO vs SIBO: Coding nuances for CPT 91065

A clinically important distinction has emerged around SIBO and Intestinal Methanogenic Overgrowth (IMO). Per peer-reviewed gastroenterology research (PMC10132719), methane-dominant breath test patterns are now classified as IMO under the 2020 ACG (American College of Gastroenterology) Clinical Guideline on SIBO (Pimentel et al., Am J Gastroenterol 2020;115(2):165-178) rather than SIBO. The distinction matters clinically because treatment protocols differ.

From a coding perspective, CPT 91065 covers both scenarios. The same code applies whether the test yields a hydrogen-dominant, methane-dominant, or mixed result. The ICD-10 diagnosis code at the time of testing reflects the working clinical question, not the test result. After results confirm a diagnosis, update the code in the patient’s record accordingly.

Hydrogen sulfide (H2S) testing adds another layer. The TrioSmart breath test (Gemelli Biotech), available as a send-out test through labs including University of Michigan MLabs, measures H2, CH4, and H2S in one session. H2S measurement may require additional coding or a different code entirely; CPT 91065 does not explicitly cover H2S.

Confirm with the performing lab and the payer before billing CPT 91065 for TrioSmart results. Gastroenterology and integrative medicine teams tracking these protocol distinctions benefit from a platform with structured direct primary care software that maintains clean protocol-level records.

Conclusion

CPT code 91065 is a single code that covers multiple clinical scenarios, which is exactly what makes it prone to billing errors. Unit count disputes, ICD-10 mismatches, and missing physician interpretation notes are the three most common denial triggers. Each is preventable with the right documentation workflow in place.

Pabau’s claims management software gives gastroenterology and primary care teams a structured way to manage CPT 91065 submissions, flag payer-specific unit rules, and keep breath test documentation audit-ready. To see how it works in practice, book a demo.

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