The CPT code for a standard diagnostic colonoscopy is 45378. For a colonoscopy with snare polypectomy, the correct code is 45385.
But the code that actually lands on the claim, and gets paid, depends on three variables:
- Findings
- Intervention
- Payer
Get any one of those wrong, and you are looking at a denial, a downcode, or a compliance flag.
Whether you are a medical coder selecting between 45380 and 45385, a billing specialist navigating Medicare’s cost-sharing waiver rules, or a GI practice manager auditing your revenue cycle, this guide gives you the decision logic and the data in one place.
This guide treats colonoscopy CPT codes as a decision tree, not a lookup table. You will find:
- Documentation requirements to support accurate coding.
- Complete colonoscopy CPT codes (45378–45398) with use cases.
- 2025–2026 Medicare reimbursement, ICD-10 support, and common billing FAQs.
- Medicare G0105/G0121, screening vs. diagnostic, and therapeutic conversion rules.
- Biopsy, polypectomy, modifiers (PT, 33, 53), and incomplete procedure coding.
- Code selection guidance with practical clinical scenarios.
- Common coding errors and how to avoid claim denials.
Which CPT codes cover colonoscopy procedures?
Colonoscopy CPT codes run from 45378 through 45398, covering diagnostic, biopsy, polypectomy, ablation, and endoscopic mucosal resection procedures.
Medicare uses HCPCS codes G0105 and G0121 specifically for preventive colonoscopy services.
The American Medical Association (AMA) publishes these codes as part of the CPT code set, and the 2026 update confirms no structural changes to the colonoscopy family.
The American Society for Gastrointestinal Endoscopy (ASGE) and CMS provide additional guidance on appropriate use.
Below is the complete reference table:
| CPT / HCPCS Code | Procedure Description | Clinical Use Case |
| 45378 | Colonoscopy, flexible; diagnostic | Standard diagnostic exam, no intervention |
| 45379 | Colonoscopy with removal of foreign body(s) | Foreign body extraction |
| 45380 | Colonoscopy with biopsy, single or multiple | Tissue sampling, cold-forceps biopsy |
| 45381 | Colonoscopy with directed submucosal injection(s) | Submucosal lift prior to resection or tattooing |
| 45382 | Colonoscopy with control of bleeding | Electrocoagulation, hemostatic clip |
| 45384 | Colonoscopy with removal of tumor(s), polyp(s), or other lesion(s) by hot biopsy forceps | Small polyp removal via hot forceps |
| 45385 | Colonoscopy with removal of tumor(s), polyp(s), or other lesion(s) by snare technique | Snare polypectomy, most common therapeutic code |
| 45386 | Colonoscopy with dilation | Stricture dilation |
| 45388 | Colonoscopy with ablation of tumor(s), polyp(s), or other lesion(s) | APC, laser, or cryotherapy ablation |
| 45389 | Colonoscopy with endoscopic stent placement | Colonic stenting |
| 45390 | Colonoscopy with endoscopic mucosal resection (EMR) | En-bloc or piecemeal EMR of large lesions |
| 45391 | Colonoscopy with endoscopic ultrasound examination | EUS at time of colonoscopy |
| 45392 | Colonoscopy with transendoscopic ultrasound-guided intramural or transmural fine-needle aspiration/biopsy(s) | EUS-FNA during colonoscopy |
| 45393 | Colonoscopy with decompression (for pathologic distention or volvulus) | Volvulus decompression |
| 45394 | Colonoscopy with band ligation(s) | Rectal varices banding |
| 45395 | Colonoscopy with resection and anastomosis | Surgical endoscopic resection |
| 45397 | Colonoscopy with transendoscopic intraluminal tube or catheter placement | Decompression tube placement |
| 45398 | Colonoscopy with band ligation(s) of hemorrhoid(s) | Hemorrhoid banding |
| G0105 | Colorectal cancer screening; colonoscopy on individual at high risk | Medicare high-risk preventive screening |
| G0121 | Colorectal cancer screening; colonoscopy on individual not meeting high-risk criteria | Medicare average-risk preventive screening |
A critical point for coders: report only the highest-level intervention performed.
If the endoscopist performs a snare polypectomy and also takes a cold biopsy at a separate site, bill 45385, the snare, not both.
Multiple endoscopy bundling rules under CMS apply; the additional procedure may be billable at a reduced rate, but the base code must reflect the most complex intervention.
What is the difference between screening and diagnostic colonoscopy coding?
The differentiation determines which code set you use and whether the patient owes cost-sharing.
Medicare screening colonoscopy coding
Medicare does not use CPT codes for preventive colonoscopy. It uses two HCPCS Level II codes:
| HCPCS Code | Patient Population | Frequency Covered | Cost-Sharing (No Polyps Found) |
| G0105 | High-risk individuals | Every 24 months | No deductible; 20% coinsurance applies |
| G0121 | Average-risk (not high-risk) | Every 10 years (age ≥50) or every 2 years for flexible sigmoidoscopy follow-up | No deductible; 20% coinsurance applies |
High-risk under Medicare means a personal history of colorectal polyps, colorectal cancer, or inflammatory bowel disease.
Also, a family history of familial adenomatous polyposis (FAP), hereditary non-polyposis colorectal cancer (HNPCC), or colorectal cancer in a first-degree relative. Use G0105 for these patients. Use G0121 for all others.
When no polyp is found, Medicare waives the Part B deductible. When a polyp is found and removed, the waiver changes, see H2 #3 below on the screening-turned-therapeutic scenario.
Commercial payer screening colonoscopy coding
For most commercial insurance plans, report CPT 45378 with modifier 33 for a preventive screening colonoscopy.
Modifier 33 identifies the procedure as an ACA-covered preventive service and generally waives patient cost-sharing.
Omitting the modifier may result in the claim being processed with standard deductibles or coinsurance. Use:
- CPT 45378 + modifier 33 for preventive screening colonoscopy
- ICD-10-CM Z12.11 for screening for malignant neoplasm of the colon
Keep in mind that some commercial plans, especially self-insured ERISA plans, are not required to follow ACA preventive cost-sharing rules.
Always verify the patient’s specific benefits before discussing expected out-of-pocket costs.
What happens when a screening colonoscopy becomes therapeutic?
When a polyp is found and removed during a screening colonoscopy, you must change the CPT code to the appropriate therapeutic code and append the correct modifier.
The screening intent does not override the procedure performed; it modifies how you report it.
This scenario is the highest-error billing area in GI endoscopy. The American Gastroenterological Association (AGA) and ASGE have both published FAQs specifically addressing it. The logic is straightforward once you know the rules.
The rule is to Report the therapeutic CPT code (e.g., 45385 for snare polypectomy) regardless of how the procedure started. Then add the appropriate modifier to signal original screening intent.
| Payer Type | Code to Report | Modifier to Append | Effect on Patient Cost-Sharing |
| Medicare | 45385 (or other therapeutic code) | Modifier PT | Deductible waived; 20% coinsurance applies |
| Commercial (ACA plan) | 45385 (or other therapeutic code) | Modifier 33 | Payer must waive cost-sharing (ACA Section 2713) |
| Commercial (non-ACA / grandfathered) | 45385 (or other therapeutic code) | Modifier 33 (or per contract) | Cost-sharing waiver not guaranteed; verify plan |
Modifier PT (colorectal cancer screening test converted to a diagnostic/therapeutic service, Medicare) was introduced specifically for this scenario.
It tells Medicare that the procedure began as a preventive screening under G0105 or G0121 but converted to a therapeutic service.
Without modifier PT, Medicare processes the claim as a standard diagnostic/therapeutic colonoscopy, the deductible applies, and patients face unexpected bills.
So for example, a 66-year-old Medicare patient, average risk, schedules a routine screening colonoscopy.
During the procedure, the endoscopist identifies and removes a 7mm sessile polyp via snare. Correct billing:
1. CPT: 45385 (snare polypectomy)
2. Modifier: PT
3. Diagnosis: Z12.11 (primary) → D12.6 (secondary, if pathology confirms adenoma)
4. Result: Deductible waived; patient owes 20% coinsurance on the allowable amount
Do not revert to G0121 when a therapeutic intervention occurs. G0121 is a screening-only code.
Once intervention happens, the clinical service has changed. Coding G0121 with a polypectomy is incorrect and will generate a claim edit from most payers.
Which CPT code applies to colonoscopy with biopsy or polypectomy?
The correct code depends on the technique the endoscopist used, not on the size or appearance of the lesion.
Cold-forceps biopsy maps to 45380; snare polypectomy maps to 45385; ablation maps to 45388; and endoscopic mucosal resection maps to 45390.
The Tri-Society Coding Guide (ASGE/AGA/ACG, 2024) establishes a coding hierarchy to resolve ambiguity.
Use the decision path below:
Biopsy Forceps
Forceps
Snare
Cryotherapy
Mucosal Resection
or Clip
Injection
When the endoscopist removes multiple polyps by the same technique, bill only one code (e.g., one 45385 regardless of polyp count).
When different techniques are used, a snare polypectomy and a separate cold biopsy at a different site, bill 45385 as the primary code.
Code 45380 may be billed separately with modifier 59 or XS to indicate a distinct site, subject to payer bundling rules and the multiple endoscopy rule.
Also, The Tri-Society guide establishes a clear hierarchy: therapeutic codes supersede diagnostic codes.
If 45385 is billed, do not also bill 45378. The therapeutic code’s work RVU already accounts for the diagnostic component of the exam.
How do you code an incomplete colonoscopy?
An incomplete colonoscopy is coded differently from a completed procedure, but it is not reported as a flexible sigmoidoscopy.
The correct code depends on whether the colonoscopy was started, why it was discontinued, and how far the procedure progressed.
When to use modifier 53
When a colonoscopy is terminated before the scope reaches the cecum, report the planned CPT code with modifier 53 (discontinued procedure).
Do not downcode to a flexible sigmoidoscopy code, and do not report a completed colonoscopy. CMS guidance in article A57342 is explicit on both points.
What qualifies as an incomplete colonoscopy?
An incomplete colonoscopy occurs when the endoscopist cannot advance the scope to the cecum because of patient intolerance, inadequate bowel preparation, anatomical obstruction, or clinical safety concerns.
The procedure is initiated, but cannot be completed as planned.
Why you should not downcode
Do not report a flexible sigmoidoscopy code simply because the cecum was not reached.
The colonoscope, bowel preparation, physician work, and sedation management all reflect a colonoscopy service.
CMS specifically instructs providers not to downcode in these situations.
Reimbursement for incomplete colonoscopy
Modifier 53 reduces reimbursement to reflect the partial service.
For CPT 45378 with modifier 53, Medicare generally reimburses about 50% of the full fee schedule amount, although the exact payment varies by locality and the point at which the procedure was discontinued.
Documentation requirements
The operative report should clearly document:
- Reason the procedure was discontinued
- Extent of insertion (e.g., advanced to the splenic flexure)
- Clinical follow-up plan (e.g., repeat colonoscopy after improved bowel preparation)
This documentation supports the use of modifier 53 if the claim is audited.
If the procedure never begins
If the procedure is canceled before scope insertion — for example, if the patient withdraws consent after preparation but before the procedure starts — do not bill the colonoscopy CPT code.
Instead, report the appropriate E&M service, if applicable.
How much does Medicare reimburse for colonoscopy CPT codes?
Medicare’s national average payment for a standard diagnostic colonoscopy (45378) is approximately $282 in the facility setting and $503 in the non-facility (office) setting.
Reimbursement for therapeutic codes scales with clinical complexity. Use the CMS Physician Fee Schedule Look-Up Tool for locality-specific rates.
The figures below reflect 2025 Medicare Physician Fee Schedule national averages. Patient cost data is sourced from Medicare.gov.
Note that rates are adjusted annually and vary by geographic area (Medicare Administrative Contractor locality). Always pull current, locality-specific data for actual billing.
| CPT / HCPCS Code | Procedure | Total Facility Fee | Patient Share (20% Coinsurance) | Non-Facility Total Fee |
| 45378 | Diagnostic colonoscopy | ~$282 | ~$56 | ~$503 |
| 45380 | Colonoscopy with biopsy | ~$318 | ~$64 | ~$567 |
| 45385 | Colonoscopy with snare polypectomy | ~$411 | ~$82 | ~$733 |
| 45388 | Colonoscopy with ablation | ~$452 | ~$90 | ~$806 |
| 45390 | Colonoscopy with EMR | ~$698 | ~$140 | ~$1,244 |
| G0121 | Medicare screening (average-risk) | ~$282 | $0 (deductible waived) | ~$503 |
| G0105 | Medicare screening (high-risk) | ~$282 | $0 (deductible waived) | ~$503 |
When two colonoscopy procedures are billed for the same patient on the same date (rare but possible in add-on scenarios), Medicare applies the multiple endoscopy rule.
The higher-valued procedure is paid at 100%; the lower-valued procedure is paid at its facility rate minus the base endoscopy rate (45378).
This prevents double-counting the diagnostic component shared by both codes.
For anesthesia, since January 2017, moderate sedation is no longer bundled into colonoscopy CPT codes.
Bill CPT 99152 – 99153 for moderate sedation provided by the same physician, or 99155 – 99157 when a separate qualified observer is present.
If anesthesia services are provided by an independent anesthesiologist, they bill using anesthesia CPT codes and are not your responsibility to report.
Which ICD-10-cm codes support colonoscopy medical necessity?
The most frequently used diagnosis codes for colonoscopy include Z12.11 for routine screening, Z86.010 for personal history of colonic polyps, and K63.5 for polyp of colon.
Code selection must reflect the documented clinical indication. Payer local coverage determinations (LCDs) may restrict which diagnosis codes are covered for a given CPT code.
When the colonoscopy converts from screening to therapeutic, sequence the primary reason for the encounter first.
For a screening that found and removed a polyp, Z12.11 remains the primary code; add K63.5 or D12.6 as secondary depending on whether pathology is pending or confirmed. This sequencing supports the modifier PT/modifier 33 claim logic.
Always cross-reference the patient’s payer LCD. Some Medicare Administrative Contractors (MACs) maintain LCDs for GI endoscopy that enumerate covered and non-covered diagnoses.
Billing a non-covered ICD-10-CM code without an Advance Beneficiary Notice (ABN) creates both a denial risk and a compliance exposure.
Frequently Asked Questions
Here are some commonly asked questions on this topic:
For commercial insurance, bill CPT 45378 with modifier 33. This signals an ACA-mandated preventive service and triggers the cost-sharing waiver. For Medicare average-risk patients, use G0121. For Medicare high-risk patients, use G0105. Do not use 45378 alone for a preventive colonoscopy on a Medicare patient, the HCPCS codes are required.
Yes, but only if the patient has a separately identifiable medical condition that requires evaluation on that same date and is documented as such. Append modifier 25 to the E&M code to indicate it is a significant, separately identifiable service performed on the same day as a procedure. Routine pre-procedure counseling for a healthy screening patient does not support a separate E&M.
G0105 is for Medicare beneficiaries who meet high-risk criteria (personal history of polyps or CRC, first-degree family history, IBD, FAP/HNPCC). G0121 is for everyone else, average-risk patients who are not high-risk. Frequency limits differ: G0105 covers every 24 months; G0121 covers every 10 years (or more frequently following certain tests). Using the wrong code affects patient eligibility determination and frequency edits.
Yes. Report the therapeutic code, for example, 45385 for snare polypectomy, regardless of screening intent. Append modifier PT for Medicare or modifier 33 for commercial ACA plans. The G0121 or G0105 code is not used when a therapeutic intervention occurs. The AGA FAQ confirms this rule directly.
No. Since January 1, 2017, moderate sedation is no longer bundled into surgical procedure codes, including colonoscopy. Bill CPT 99152 (moderate sedation, first 15 minutes, age 5+) and 99153 for each additional 15-minute increment when the performing physician also provides the sedation. If a separate observer is present, use 99155 – 99157. If an independent anesthesiologist provides MAC or general anesthesia, the anesthesia codes are their responsibility.
Under the multiple endoscopy rule, when two colonoscopy codes are billed for the same patient on the same date, CMS pays the higher-valued code at 100% and the lower-valued code at its difference above the base endoscopy (45378). This prevents double-counting the shared diagnostic component. The rule applies to same-day, same-specialty services.
