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; prior authorization is required by some commercial insurers, including Providence Health Plan for Medicare-only policies.

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

Breath testing claims are among the most frequently miscoded in gastroenterology. CPT Code 91065 covers a specific, well-defined procedure, yet documentation gaps, incorrect unit counts, and unsupported ICD-10 pairings drive a disproportionate share of denials. Getting this code right starts with understanding exactly what it covers and where payers draw the line.

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

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.

The four primary clinical applications covered under CPT 91065 are:

• 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 Rome IV criteria; 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.

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. Labs such as 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 2 units, verify the payer’s specific policy. Submitting 2 units 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. Good features that save private practices time include automated modifier flagging within billing workflows.

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 Physician 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.

Providence Health Plan’s Medicare-only medical policy lists CPT 91065 as requiring prior authorization. This is a payer-specific requirement; it does not apply universally across all Medicare Advantage or commercial plans. Always check the specific plan’s prior authorization list before ordering the test.

Moda Health’s medical necessity criteria document names CPT 91065 as a covered code for hydrogen breath testing, alongside companion code CPT 82542 (quantitative column chromatography). 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 real time savings for billing teams.

Reimbursement rates for CPT 91065

Medicare reimbursement for CPT 91065 typically falls in the range of $30 to $60 depending on geographic practice expense adjustments and the care setting. Commercial payer rates vary significantly and are not published uniformly. Use the FastRVU 2026 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 preparatory diet and fasting requirements. 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. The approach to medical forms at healthcare practices has shifted toward digitized structured fields, reducing gaps in billing documentation.

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 code combinations for CPT 91065

CPT 91065 is sometimes submitted alongside other codes depending on the clinical workflow. Two 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 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 Rome IV criteria 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 from 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.

Continue your research

Managing complex billing across a practice? Practice management software covers the key capabilities gastroenterology and primary care teams need to reduce administrative burden.

Concerned about compliance in your documentation workflows? HIPAA compliance for medical offices outlines what structured records and access controls need to cover.

Looking to streamline intake and pre-test documentation? Digital forms help practices capture structured patient information before the appointment, reducing gaps in billing records.

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