When coding for colonoscopies for Medicare patients it is crucial to understand the following:

  1. What is a screening colonoscopy?
  2. Which codes are applicable?
  3. Is a modifier required?

In some scenarios, it is also helpful to know what coverage limitations apply.  Let’s take a closer look!

Screening Colonoscopies

A screening colonoscopy is provided to a patient in the absence of signs or symptoms based on the patient’s age, gender, medical history, and family history and typically based on medical guidelines. The formal definition of “screening” describes a colonoscopy routinely performed on an asymptomatic person for the purpose of testing for cancer or colorectal polyps.

Now, it is not that uncommon for the surgeon to remove one or more polyps at the time of a screening colonoscopy, which would be a therapeutic procedure, even though the procedure  began as a screening.  Whether a polyp or cancer is ultimately found does not change the screening intent of that procedure.

Two Sets of Codes

The Centers for Medicare and Medicaid Services (CMS) developed the HCPCS codes to differentiate between screening and diagnostic colonoscopies in the Medicare population.  When choosing a CPT/HCPCS code, be sure to link the appropriate diagnosis code based on documentation.

Keep in mind that for screening colonoscopies, the screening diagnosis is always reported as primary.  If found, the polyp(s) is reported as a secondary diagnosis.  However, , the provider should not report the screening colonoscopy code for the CPT but rather the code for the diagnostic or therapeutic procedure performed.

HCPCS/CPT Description
45378 Colonoscopy, flexible, diagnostic
G0105 Screening colonoscopy on individual at high risk
G0121 Screening colonoscopy on individual not meeting the criteria for high risk
ICD-10-CM Description
Z12.11 Encounter for screening for malignant neoplasm of colon
Z80.0 Family history of malignant neoplasm of digestive organs
Z86.010 Personal history of colonic polyps
CMS defines ‘high risk’ as a patient with a:

  • close relative (sibling, parent, or child) who has had colorectal cancer or an adenomatous polyp
  • family history of familial adenomatous polyposis
  • family history of hereditary nonpolyposis colorectal cancer
  • personal history of adenomatous polyps
  • personal history of colorectal cancer
  • inflammatory bowel disease, including Crohn’s Disease, and ulcerative colitis

Modifier PT

CMS developed the PT modifier to indicate that a colonoscopy scheduled as a screening was converted to a diagnostic or therapeutic procedure.  The PT modifier (colorectal cancer screening test, converted to diagnostic test or other procedure) is appended to the CPT code.

For example, if a non-high-risk patient presented for a screening colonoscopy and the provider performed a polyp removal with hot biopsy forceps, you would report code 45384-PT with a primary diagnosis code of Z12.11 followed by the appropriate polyp diagnosis code (e.g., K63.5).

Some commercial payers follow CMS guidelines for the use of PT modifier, but some do not.  It is always good to check your payer guidelines before filing the claim to verify specific requirements.

Colorectal Cancer Screening Coverage

Several organizations have issued guidelines on colorectal rectal screening. While most guidelines recommend routine screening for adults starting at age 50, the frequency and screening age, as well as the preferred screening method can differ. If the patient is considered high-risk for colorectal cancer, this can also change screening guidelines.

Per CMS, screening colonoscopies are covered once every 120 months, or 48 months after a previous flexible sigmoidoscopy, and there is no minimum age requirement.  For high-risk patients, a colonoscopy is covered once every 24 months.  Although the screening is covered, if a polyp of other tissue is found and removed during the colonoscopy, the patient may still be responsible for 20% of the Medicare-approved amount for the physician services, and a copayment in the hospital setting.  Part B deductible doesn’t apply.

Check out these resources for more information:




Mary is a consultant for The Haugen Consulting Group with over 25 years of health care industry experience. She started her career in Orthopedics which was her passion for decades. In addition to Orthopedics, she provides expertise in other specialties such as Anesthesia, Ambulatory Surgery Center, as well as most surgical specialties . She has experience working the professional fee side of coding, audit, education as well as compliance, serving both coders and physicians, as well as the surgical side. She is a Certified Professional Coder (CPC), Certified Professional Medical Auditor (CPMA), Certified Anesthesia Professional Coder (CANPC) Certified Ambulatory Surgery Center Coder (CASCC) and Certified Orthopedic Surgery Coder (COSC).

During her free time, she loves to do crafts, enjoys the outdoors, and the Broncos! She has 4 daughters, and 10 grandchildren which light up her life.


  1. Laura Terry

    I am getting a rejection for the icd 10 z86.010 – inappropriate dx code billed in primary position we have been bill this code as primary for years has something changed 2023 and should i add the z12.11 to the primary and z86.010 secondary position ?

    • kkluglein

      Hi Laura,

      Without seeing the documentation for each scenario, we would not be able to provide specific sequencing guidance as you would need to review documentation, ICD10 guidelines, and payor guidelines.

      Occasionally physicians use different verbiage for screening colonoscopies. If the word “surveillance” is documented, we would recommend coding this as a screening (Z12.11), followed by any findings, as well as the personal history of colonic polyps (Z86.010) sequenced in that order.

      If you would like our experts to look at this in further detail, please email us for information and pricing regarding our coding hotline at hahelp@thehaugengroup.com

      Thank you!

  2. debbie Bassett

    Hi, We have been having trouble getting paid when billing 45380 and 45385 with PT or 33 depending on insurance saying Z12.11 is not a covered Dx any advise

    • kkluglein

      Hi Debbie – We recommend checking with the insurance carrier regarding their requirements for submitting claims for preventative colonoscopies. The dx and modifiers appear to be accurate so this sounds like a claims processing error on behalf of the carrier or policy driven.

  3. Tracy

    I would love to hear how you code a colonoscopy for surveillance of Ulcerative Colitis with no findings. I’m specifically referring to commercial plans that do not consider IBS high risk. My opinion is to code 45378 with dx code K51.00. A coworker codes 45378 with dx Z87.19, K51.00. I do not believe Z78.19 is correct. The patient has not had any recent flares, but is still receiving treatment for the condition.

    • kkluglein

      Hi Tracy! Due to all of the variances between commercial payers, we are unable to offer commercial payer advice.

      We always recommend checking with the individual payer for payer requirements. If all else fails, follow CMS guidance and appeal accordingly.

      CMS defines ‘high risk’ as a patient with a:
      • close relative (sibling, parent, or child) who has had colorectal cancer or an adenomatous polyp
      • family history of familial adenomatous polyposis
      • family history of hereditary nonpolyposis colorectal cancer
      • personal history of adenomatous polyps
      • personal history of colorectal cancer
      • inflammatory bowel disease, including Crohn’s Disease, and ulcerative colitis



    Since Medicare allows a screening colonoscopy every 10 years, is a modifier needed when the doctor performs a Medicare screening colonoscopy with no findings but wants to repeat colonoscopy in 5 years due to suboptimal bowel preparation?

    Thank you

    • kkluglein

      Hi Mary! This is a tough one to answer as it depends on how this was initially submitted. Typically with poor prep it would have been submitted with a modifier initially and then repeated within a few days (not a few years). If it was submitted as a completed procedure and paid the first time under preventative, chances are Medicare will not pay for this under preventative therefore the patient will be responsible for their portion.

  5. Nancy Zihlman

    I was wondering if the PT modifier has to go on both lines if the doctor removes polyps for snare and cold biopsy for a colonoscopy.
    Also, do you do the same for a ACS facility claim?

    • kkluglein

      Hi Nancy – Thank you so much for your inquiry. Here is the response from our team:

      The modifier PT (or 33 depending on payer) should be added to each CPT code if the patient is scheduled as a screening but ends up with a biopsy or something else. The same guidelines are applicable to ASC’s as well as Anesthesia providers.

  6. Rob O


    I have been trying to find this information everywhere with no luck

    We have a patient that qualified for the G0121 just under 10 yrs ago. Since that G code is only good for 10 yrs, what code do we use for his latest screening? No issues found. If we use a CPT code, will Medicare cover the screening?

    • kkluglein

      Hi Rob –
      Unfortunately Medicare has strict guidelines regarding coverage for G0121. You can file it with 45378. However it would not be covered under preventive since the 10 year mark has not passed so the patient will be responsible for his coinsurance and deductible.

      Here’s the link for the Medicare Claims processing manual that may provide additional information for you.


  7. Monica R

    Hi, we have a commercial plan denying our claims for screening colonoscopies for not matching the surgeon’s bill. We use CPT 45378 and the surgeon uses G0121. We are an ASC in network with the plan BX and this plan uses BX pricing and contract to reimburse our claims, however, our claims keep getting denies. Any suggestions?

    • kkluglein

      Hi Monica,
      Our team suggests “Check with the Payer for their specific guidelines/requirements. If the provider is using the G code, its possible that this carrier follows CMS.”
      Thank you!

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