HCPCS code G0105: Colonoscopy on individual at high risk

Key takeaways

HCPCS code G0105 covers colorectal cancer screening colonoscopy for Medicare patients at high risk, billed under Medicare Part B.

High-risk criteria include personal history of colorectal cancer, adenomatous polyps, inflammatory bowel disease, or a qualifying family history.

G0105 is covered once every 24 months; billing it more frequently or using it for average-risk patients triggers denials and audit risk.

Pabau’s claims management software automates eligibility checks, modifier application, and claim scrubbing to reduce G0105 denials.

Most G0105 claim denials trace back to one of three mistakes. Coders pick the wrong code for the patient’s risk level, miss the 24-month interval, or skip documenting the high-risk basis. Billing staff who understand the difference between G0105 and G0121 from the start avoid the bulk of these rejections. Eligibility accuracy is the single highest-leverage point in preventive service billing.

This reference covers the official description, eligibility criteria, ICD-10-CM pairings, applicable modifiers, reimbursement rates, documentation requirements, and denial patterns for HCPCS code G0105.

HCPCS code G0105: Definition and Medicare Part B context

HCPCS code G0105 describes colorectal cancer screening; colonoscopy on individual at high risk. It is an HCPCS Level II G-code maintained by the Centers for Medicare and Medicaid Services (CMS). Medicare Part B bills it for preventive colonoscopy services performed on beneficiaries who meet the CMS-defined high-risk criteria.

G-codes like G0105 exist because Medicare uses HCPCS Level II codes for certain preventive services rather than the standard CPT procedure code set. For colorectal cancer screening specifically, CMS uses G0105 (high-risk) and G0121 (average-risk) instead of the diagnostic colonoscopy CPT codes in the 45378-45398 range. This distinction matters for billing: submitting a CPT code where a G-code is required results in automatic denial.

The code is covered under CMS’s Medicare Physician Fee Schedule and is governed by National Coverage Determination (NCD) 210.3 for colorectal cancer screening. Local Coverage Determinations (LCDs) issued by Medicare Administrative Contractors (MACs) may add jurisdiction-specific criteria.

Who qualifies as high risk? G0105 high-risk criteria

CMS NCD 210.3 defines high risk for G0105 eligibility. A Medicare beneficiary qualifies as high risk for colorectal cancer screening if they have at least one of the following documented conditions:

• Personal history of colorectal cancer
• Personal history of adenomatous polyps (adenomas)
• Inflammatory bowel disease (IBD), including Crohn’s disease or ulcerative colitis
• Family history of colorectal cancer or adenomatous polyps in a first-degree relative before age 60, or in two or more first-degree relatives at any age
• Family history of adenomatous polyposis or hereditary nonpolyposis colorectal cancer (Lynch syndrome)

Documentation of the specific high-risk condition must appear in the medical record before the procedure date. A note that reads only “screening colonoscopy” without a stated clinical basis for high-risk status is the leading documentation deficiency in G0105 audits. Verify the patient’s insurance eligibility and high-risk status before scheduling.

G0105 vs G0121: High-risk vs average-risk colonoscopy coding

The most common selection error in colorectal cancer screening billing is using G0105 and G0121 interchangeably. They are not interchangeable. Selecting the wrong code for the patient’s risk level causes problems either way. The wrong code for the benefit triggers a denial, and upcoding a low-risk patient to the high-risk benefit creates compliance liability.

When a patient has documented high-risk factors, G0105 is the required code regardless of the patient’s age. Using G0121 for a documented high-risk patient undercodes the benefit and may result in a frequency denial on the next eligible screening interval.

Medicare coverage rules and frequency limitations

Medicare Part B covers HCPCS code G0105 once every 24 months for beneficiaries who meet the high-risk criteria. The 24-month measurement is from the date of the last covered G0105 colonoscopy, not from the calendar year. Claims submitted before the 24-month window elapses will deny as frequency violations.

Cost-sharing rules under the Affordable Care Act (ACA) waive the Medicare Part B deductible and coinsurance for G0105. This applies only when the procedure remains a screening colonoscopy throughout. This waiver does not carry over automatically if the procedure converts to a diagnostic or therapeutic colonoscopy during the same session. Patient financial counseling before the procedure should address this potential cost-sharing change.

For practices managing high patient volumes, tracking the 24-month interval manually is a common source of billing errors. Revenue cycle management workflows that flag upcoming eligible dates reduce frequency-related denials. Automated eligibility tracking tied to prior claim history removes the guesswork from scheduling the next screening.

ICD-10-CM diagnosis codes for G0105

Every G0105 claim requires a supporting ICD-10-CM diagnosis code that establishes the clinical basis for high-risk status. The primary diagnosis code must match the documented high-risk condition, not a generic screening code. The CDC/NCHS ICD-10-CM web tool provides the authoritative lookup for current fiscal year codes.

Use the most specific code available for the documented high-risk condition. Verify all listed codes against the current CMS ICD-10-CM tabular list, as ICD-10-CM is updated annually each October 1. Submitting an inactive or revised code causes a claim edit failure at the clearinghouse level before the claim reaches the MAC.

Related colonoscopy CPT codes and HCPCS codes

G0105 does not exist in isolation. Billing staff need to understand the full colonoscopy code family to handle converted procedures, sequencing, and crosswalks correctly.

The CPT colonoscopy codes (45378-45398) are used for diagnostic or therapeutic procedures. They apply to G0105 billing when the procedure converts from screening to diagnostic or therapeutic during the same session. See the conversion section below for coding rules.

When a screening colonoscopy converts to diagnostic or therapeutic

A physician begins a procedure under G0105 intent but removes a polyp or takes a biopsy. The code changes. This conversion scenario is the single highest-risk area for G0105 billing errors and Medicare Recovery Audit Contractor (RAC) scrutiny. CMS billing guidance (Article ID 55069) governs converted colonoscopy coding.

The coding steps for a converted procedure are:

1. Replace G0105 with the appropriate therapeutic CPT code (45380 for biopsy, 45385 for polypectomy, 45378 for diagnostic conversion).
2. Append modifier PT to the CPT code to indicate the procedure began as a colorectal cancer screening test.
3. Report the screening-intent ICD-10-CM diagnosis code (Z12.11, encounter for screening for malignant neoplasm of colon) as the primary diagnosis, with the finding code listed secondary.
4. Confirm patient cost-sharing implications: the ACA deductible waiver may not apply once the procedure converts to diagnostic. Patient responsibility can change.

Modifier PT is critical in this scenario. It signals to Medicare that the procedure started as a preventive screening, which affects how cost-sharing waivers apply. Without modifier PT on a converted colonoscopy, the claim processes as a purely diagnostic procedure. The patient then loses access to any remaining screening benefit protection. Always confirm current modifier PT guidance from your MAC, as CMS transmittal updates can affect application rules.

G0105 reimbursement rates and place of service

Medicare reimbursement for G0105 varies by place of service (POS). CMS publishes updated rates annually through the Medicare Physician Fee Schedule. Always verify current rates against the CMS Physician Fee Schedule lookup tool for your geographic locality before quoting figures. Rates are subject to annual adjustment.

The non-facility rate is higher because the physician’s practice bears all overhead costs. The facility rate (hospital outpatient or ASC) is lower for the professional claim because the facility receives a separate facility fee. When reviewing electronic remittance advice for G0105 payments, confirm the rate applied matches the POS code submitted. Mismatched POS codes are a common payment discrepancy source.

Documentation requirements for G0105

Inadequate documentation is the primary reason G0105 claims survive the initial payer edit but fail on post-payment audit. CMS and MAC auditors look for specific chart elements that support both the high-risk classification and the screening intent of the procedure. Good billing documentation practices begin with the pre-procedure intake, not the operative note.

Required documentation elements for a defensible G0105 claim include:

• High-risk condition documented: The medical record, referral, or history and physical must state the qualifying condition, such as adenomatous polyps removed previously. It cannot appear only in the ordering field.
• Physician order: A signed order for screening colonoscopy that references the high-risk indication.
• Procedure report: Operative note specifying scope type, extent of examination, patient preparation adequacy, findings, and any tissue removed.
• Pathology report: Required when biopsy or polypectomy is performed; must correlate with CPT code billed if procedure converted.
• Anesthesia documentation: If moderate sedation or anesthesia is provided separately, documentation must support the additional service billed.
• Interval documentation: Chart must reflect that 24 months have elapsed since any prior G0105 or G0121 colonoscopy.

Digital intake and consent forms that capture high-risk history fields catch missing documentation at the source. A structured superbill preparation workflow that requires the billing code selection to match the documented indication prevents the most common mismatch errors. A pre-claim documentation checklist for G0105 is standard practice for practices managing medical billing compliance.

Common billing errors and how to avoid them

G0105 claims are denied for predictable reasons. The following errors account for the majority of rejections and RAC audit findings for colorectal cancer screening billing.

• Wrong code selection: Using G0121 for a documented high-risk patient, or using a CPT diagnostic code (45378) instead of G0105 for a Medicare screening colonoscopy. Medicare requires G-codes for preventive colonoscopy, not CPT codes.
• Frequency violation: Submitting G0105 before 24 months have elapsed from the last covered colonoscopy. Check prior claim history at the MAC portal before scheduling.
• Missing or mismatched ICD-10-CM code: Submitting Z12.11 (screening encounter) alone, without a supporting high-risk diagnosis code, causes a denial. The same applies to a code that doesn’t match the documented condition. Z12.11 alone does not support G0105 medical necessity.
• Conversion coding errors: Continuing to bill G0105 after a polyp is removed or biopsy taken. The code must change to the appropriate CPT code plus modifier PT.
• Modifier PT omitted on converted procedures: Billing a CPT code without modifier PT removes the patient’s ACA cost-sharing protections. This happens when the procedure began as a screening.
• Incomplete documentation: No explicit high-risk condition documented in the chart, or documentation exists but in an addendum added after audit notification.

Effective denial management for G0105 starts with a pre-submission claim scrub. The scrub checks frequency, ICD-10 validity, and modifier logic before the claim leaves the practice. Cross-checking rejections against denial codes in medical billing catches recurring patterns early. Clean claim submission rates for colonoscopy coding improve significantly when the scrub is automated rather than manual.

How practice management software supports G0105 billing

Manual G0105 billing workflows carry three specific failure points:

• Frequency checks done by memory.
• Modifier selection left to individual coders.
• ICD-10 pairing reviewed only after a denial arrives.

Each failure point is preventable with the right systems in place.

Practice management platforms that integrate scheduling, charting, and billing can prevent each of these failure points before it causes a denial:

• Flag patients approaching their 24-month eligibility window.
• Prompt coders when a procedure note indicates findings that trigger a code conversion.
• Validate ICD-10 pairings against active code sets before claim submission.

Practices that automate their G0105 eligibility and code validation workflows consistently report fewer denials on colorectal cancer screening claims. That beats relying on coder knowledge alone.

Pabau’s claims management software supports this workflow through built-in claim scrubbing and eligibility verification tools. Billing teams catch G0105 issues before submission instead of after a denial. Reviewing your overall revenue cycle management approach alongside code-specific workflows is worth the investment.

Automate your colonoscopy billing workflow

Pabau’s claims management tools help gastroenterology and primary care practices track G0105 eligibility dates, apply the right modifiers automatically, and scrub claims before submission. Fewer denials. Less rework.

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Conclusion

G0105 billing errors are rarely random. They cluster around a handful of predictable failure points: wrong code selection, frequency violations, missing modifiers on converted procedures, and incomplete documentation. Getting these right requires both coder training and system-level controls that catch errors before submission.

Pabau’s claims management tools give gastroenterology and primary care billing teams the eligibility verification and claim scrubbing they need. Remittance tracking keeps colorectal cancer screening claims clean. To see how Pabau handles colonoscopy billing workflows end to end, book a demo.

Continue your research

Need to understand how claims move from submission to payment? Medical claims clearinghouse guide explains the full electronic claim pathway and where G0105 claims can stall.

Want to reduce billing denials across your practice? Denial codes in medical billing breaks down the most common remark and reason codes your team will see on colonoscopy remittances.

Looking to credential with Medicare for colonoscopy services? Getting credentialed with insurance companies covers the MAC enrollment steps for Medicare Part B provider participation.

Frequently asked questions