What Is CPT Code 91065?
CPT code 91065 is a diagnostic test code that bills the breath hydrogen or methane test, a non-invasive study that measures gas levels in a patient’s breath after ingesting a sugar substrate to detect lactase deficiency, fructose intolerance, bacterial overgrowth, or oro-cecal transit problems. The code covers the entire test as a single unit, from substrate ingestion through interval breath sampling to final interpretation and report.
Coverage varies by diagnosis. Medicare reimburses CPT 91065 for lactose malabsorption under NCD 100.5 but has historically treated small intestinal bacterial overgrowth (SIBO) indications as non-covered or experimental under several Medicare Administrative Contractor policies, which is the single biggest source of denials for this code.
Only one unit bills per test. Regardless of how many breath samples are collected or how long the study runs for the same patient encounter, 91065 is reported once per administered challenge.
Documentation drives the claim. Payers expect the substrate used, sample time intervals, symptom history, prior conservative treatment history, and a documented interpretation tied to a supporting ICD-10 code. Missing any of these elements is the most preventable reason practices see denials on this code.
What CPT 91065 Actually Bills For
The breath hydrogen or methane test is one of the more procedurally simple codes a GI practice bills, but the workflow behind it is what payers scrutinize. The patient typically fasts 8 to 12 hours and avoids smoking, certain antibiotics, and fermentable foods for 24 hours beforehand. On the day of the test, staff collect a baseline breath sample, the patient ingests a substrate solution (commonly lactose, fructose, glucose, or lactulose depending on the suspected condition), and additional breath samples are collected at set intervals, often every 15 to 30 minutes, for up to two hours. The ordering physician or a qualified technician analyzes the hydrogen and methane concentrations and documents an interpretation.
CPT 91065 typically does not require a modifier. Modifier 26 (professional component) and modifier TC (technical component) apply only when the reading and the administration are split between two billing entities, and modifier 59 is reserved for genuinely distinct services on the same day, not for repeat breath samples within a single test.
One question we hear constantly from practice managers is whether a separate office visit can be billed on the same day as the breath test. The answer depends on whether the visit is separately identifiable and documented independently from the test order itself. If the physician performs a distinct clinical evaluation that goes beyond simply ordering and interpreting the test, modifier 25 can be appended to the E/M code. Under the proposed 2027 Medicare same-day billing rules, the lower-valued service in that scenario would be reimbursed at 50 percent, making accurate documentation and modifier compliance on same-day claims even more critical.
Does Medicare Cover CPT 91065 for SIBO?
Medicare generally covers CPT 91065 when the diagnosis supports lactose malabsorption, but coverage for SIBO indications is inconsistent and denied outright under several Medicare Administrative Contractor policies. Under NCD 100.5, Medicare covers the breath hydrogen concentration test specifically for the evaluation of lactose malabsorption. SIBO testing using lactulose or glucose substrates falls outside this national coverage determination, leaving coverage decisions to the local MAC.
This distinction is where most GI practices lose revenue on this code. A hydrogen breath test ordered for classic lactose intolerance symptoms, tied to ICD-10 code E73.9 or K90.4, and supported by a documented dietary trial, is a routine and reliably paid claim. The identical test ordered to rule out SIBO, without a payer-specific coverage check first, risks an automatic denial that has nothing to do with how the test was coded and everything to do with the diagnosis it was billed against.
In our experience matching providers with billing partners, practices that front-load the coverage check into the scheduling workflow rather than the appeals process see this denial category largely disappear. Before scheduling a SIBO-indicated breath test for a Medicare patient, verify the local coverage determination for the ordering MAC. Several commercial payers cover SIBO testing that Medicare excludes, so the coverage landscape varies by plan, not by code.
ICD-10 Codes That Support Medical Necessity
The diagnosis code appended to CPT 91065 has to match the clinical reason the test was ordered, or the payer has no basis to determine medical necessity. A mismatch between the substrate used and the diagnosis billed is a common, easily avoidable denial trigger. Providers often come to us after repeated denials on this code, and the root cause is almost always a default diagnosis code copied from a prior encounter rather than the specific code that matches the substrate protocol ordered.
| Substrate Used | Suspected Condition | Common ICD-10 Code | Typical Medicare Response |
| Lactose | Lactose intolerance / malabsorption | E73.9 or K90.4 | Generally covered with documented symptoms |
| Fructose | Fructose intolerance | K90.4 | Coverage varies by contractor |
| Lactulose or glucose | Small intestinal bacterial overgrowth (SIBO) | K90.4 or K63.89 | Frequently non-covered; verify LCD first |
| Glucose | Oro-cecal transit evaluation | R19.4 or provider-documented motility code | Coverage varies; document symptom-driven necessity |
Attach the ICD-10 code that reflects the actual clinical question the physician was answering, not a default code carried over from the previous encounter. The screening-versus-diagnostic distinction that drives so many colonoscopy denials in gastroenterology billing has a direct parallel here: the substrate and the diagnosis must tell the same clinical story, or the claim gets flagged.
How to Avoid the Top Denial Reasons for CPT 91065
Most 91065 denials repeat the same handful of root causes. Across the billing companies we vet, the practices that fix these before submission prevent the majority of rework on this code.
Verify SIBO coverage before scheduling. Confirm the Medicare Administrative Contractor’s local coverage determination, or the commercial payer’s medical policy, before ordering a SIBO-indicated test for a patient whose plan may exclude it.
Document the substrate and intervals in the note. The clinical note should name the substrate given and the sampling schedule, not just state “breath test performed.”
Record the conservative treatment history. Note any prior dietary trial, such as two weeks of lactose avoidance, since payers use this to establish medical necessity.
Bill one unit per complete study. Repeat breath samples within the same test are part of the single unit; they are not separately billable readings.
Match the ICD-10 code to the substrate. A lactulose-based SIBO protocol billed against a lactose-intolerance diagnosis code creates an internal inconsistency the payer will flag.
Skip modifiers unless a split billing arrangement applies. Adding modifier 59 or repeat-procedure modifiers to a routine single-session test invites unnecessary scrutiny.
Confirm which provider is authorized to interpret. Some payers require the interpreting clinician to be the ordering physician or a credentialed specialist; verify this in your payer contract before billing.
If your practice is seeing repeat denials on breath testing, the pattern is almost always payer-specific, not code-specific. Get matched with a vetted GI billing partner who can audit your last quarter of 91065 claims and show you exactly where the coverage gap sits. Gastroenterology Billing has connected more than 2,000 providers across all 50 states, with over 15 years in medical billing and rates starting as low as 2.95%.
2026 Reimbursement and Fee Schedule for CPT 91065
Under the 2026 Medicare Physician Fee Schedule, CPT 91065 has a global allowable of approximately $120, depending on place of service and geographic locality. The amount may vary by MAC region. Commercial payer reimbursement is typically 120 to 200 percent of the Medicare rate, depending on the provider’s contract.
The most common issue we see providers run into with reimbursement on this code is not the rate itself but the frequency of write-offs disguised as expected revenue. A claim denied for medical necessity or non-covered indication still shows up as a submitted charge, but the payment is zero. When a practice runs a high volume of SIBO-indicated breath tests against payers that do not cover them, the gap between billed charges and actual collections on 91065 can be significant, and it usually does not surface until someone runs a code-level collections report.
If your practice bills CPT 91065 regularly, pull a payer-by-payer collection rate for this code over the last two quarters. Any payer paying below 70 percent of submitted charges is worth investigating, because the shortfall is almost certainly coverage-related, not fee-schedule-related.
What Is the Difference Between CPT 91065 and CPT 83013?
CPT 91065 and CPT 83013 are both breath tests, but they diagnose entirely different conditions and are not interchangeable. CPT 91065 measures hydrogen or methane to evaluate carbohydrate malabsorption and bacterial overgrowth, while CPT 83013 measures urease activity to detect Helicobacter pylori infection.
The two codes get confused during prior authorization because both involve a patient breathing into a collection device, and staff sometimes request authorization for the wrong one. The ordering physician has to specify which test is intended, since an authorization obtained for 83013 will not cover a claim submitted under 91065, and vice versa. If your practice regularly performs both test types, flag this distinction in your scheduling template so front-desk staff request the correct authorization the first time.
A Real Denial Scenario Worth Knowing
A mid-size GI practice billed CPT 91065 for a Medicare patient with suspected SIBO, using a lactulose substrate and an ICD-10 code for unspecified abdominal pain rather than a malabsorption-specific code. The claim was denied as not medically necessary, and the practice resubmitted twice with the same diagnosis code before catching the root cause. By the time the claim was corrected and appealed, more than 90 days had passed, pushing the claim past several commercial timely-filing windows and turning a routine $85 to $120 reimbursement into a written-off balance.
The fix took five minutes; the delay in identifying it cost the practice the claim entirely. This is the exact failure pattern a billing partner familiar with GI-specific coverage policy is built to catch before submission, not after denial. In our experience matching providers with billing partners, the practices that flag SIBO coverage at the scheduling step rather than the appeals step save more revenue on this single code than they realize.
Frequently Asked Questions
Stop losing revenue to payer-specific breath test denials. Tell us about your practice and get matched with a vetted medical billing company that already knows how your payers handle CPT 91065. Gastroenterology Billing has connected more than 2,000 providers across all 50 states, with over 15 years in medical billing and rates starting as low as 2.95%. Finding a match is 100% free for providers.
Does CPT 91065 require a modifier?
Generally no. CPT 91065 typically bills without a modifier. Modifiers 26 and TC apply only when the technical administration and professional interpretation are billed separately by different entities, and modifier 59 applies only to genuinely distinct procedures, not repeat samples within one test.
How many times can CPT 91065 be billed for the same patient?
CPT 91065 bills once per complete test session. If a physician orders repeat testing on a different day for a new clinical reason, that is a separate, distinct claim with its own supporting documentation, not an additional unit on the original claim.
What is the difference between CPT 91065 and CPT 83014?
CPT 91065 is the general hydrogen or methane breath test for malabsorption and bacterial overgrowth. CPT 83014 and 83013 are Helicobacter pylori breath test analysis codes for a completely different clinical question. Confirm which test the physician ordered before selecting a code.
Can a technician administer and interpret the CPT 91065 test?
A technician can typically administer the test and collect samples, but interpretation requirements vary by payer. Some plans require the interpreting provider to be a licensed physician or qualified practitioner. Verify this in your payer contract before billing.
Is CPT 91065 covered by commercial insurance the same way as Medicare?
Not necessarily. Commercial payers set their own medical policies for breath testing, and some cover SIBO indications that Medicare excludes under NCD 100.5, while others are more restrictive. Always check the specific plan’s medical policy rather than assuming Medicare’s coverage rules apply universally.
What is NCD 100.5 and how does it affect CPT 91065?
NCD 100.5 is the Medicare National Coverage Determination for the breath hydrogen concentration test. It covers the test for evaluating lactose malabsorption but does not extend national coverage to SIBO or transit-time indications, leaving those coverage decisions to each Medicare Administrative Contractor’s local policy.
How much does Medicare reimburse for CPT 91065?
Under the 2026 Medicare Physician Fee Schedule, the national allowable for the global service is approximately $120, though it varies by MAC region and place of service. Commercial payer reimbursement is typically 120 to 200 percent of the Medicare rate depending on the provider’s contract.
What documentation is required for CPT 91065?
Payers expect the substrate used, sample time intervals, the patient’s symptom history, prior conservative treatment such as a dietary trial, and a documented clinical interpretation tied to a supporting ICD-10 code. Claims missing any of these elements are commonly denied for insufficient documentation.
