DME Billing for Continuous Glucose Monitors: Codes, Coverage, and Denials

An efficient DME billing runs on matching the right HCPCS code to the right equipment, and continuous glucose monitors are one of the more code-sensitive categories today. Get the device type wrong, skip a required verification step or bill a bundled supply separately, and DME billing for CGMs denies claims in ways that have nothing to do with whether the patient actually needed the equipment.

For Medicare-covered CGMs that meet the DME benefit requirements, four HCPCS codes anchor this corner of DME billing: E2102 and E2103 for the CGM equipment, and A4238 and A4239 for the related supply allowances. Devices that don’t meet DME benefit-category requirements are handled differently and generally fall outside this framework.

Today CGM billing is drawing more attention within DME billing generally, and not less. The OIG found that Medicare payments for CGM supplies exceeded retail market prices by approximately $290 million, which is a great deal during the one-year period reviewed. Part of a broader 2025 HHS Office of Inspector General report also identified at least $7 million in potential overpayments associated with improper coding. Suppliers handling DME billing for this category should ensure their coding and documentation processes are accurate before that scrutiny increases further.

Related Reading: Your Search for a Perfect DME Billing Partner Ends with Sunknowledge

Adjunctive vs. Non-Adjunctive in CGMs: Why the Distinction Matters in DME Billing Operations

CGMs fall into two coverage categories, and which one applies determines the codes that follow. Non-adjunctive CGMs are accurate enough to support treatment decisions, including insulin dosing, without a confirmatory finger stick test. Most CGMs Medicare covers today fall into this category and are billed under E2103/A4239.

However, adjunctive CGMs require the user to verify glucose levels or trends with a standard home blood glucose monitor before making treatment decisions. These are billed under E2102/A4238.

This distinction directly affects HCPCS code selection and coverage. Using an incorrect device or supply code combination for the CGM type actually dispensed can result in an incorrect-coding denial. A stricter standard than most DME billing categories applies here, since it hinges on a device classification rather than just the equipment itself.

PDAC Coding Verification and the Product Classification List

Both E2102 and E2103 carry a requirement most DME billing categories don’t: the specific device being billed must have gone through coding verification review by the Pricing, Data Analysis and Coding (PDAC) contractor and appear on the Product Classification List (PCL) for that exact code. If a CGM system is billed using E2102 or E2103 but isn’t listed on the PCL for that particular code, CMS specifies the claim will be denied as incorrect coding.

How to Verify a CGM on the PCL Before Billing

• Identify the specific device and manufacturer being dispensed
• Check the PDAC’s Product Classification List for the device under the applicable code (E2102 or E2103)
• Confirm whether the device is adjunctive or non-adjunctive since this determines which code and supply allowance apply
• Select the correct supply allowance code (A4238 for adjunctive, A4239 for non-adjunctive)
• Ensure the coverage documentation is in place before submission
• Submit the claim with the verified code combination

Skipping the PCL check before dispensing is one of the more preventable coding errors in this category, since the verification step happens before the claim is ever built.

The Supply Allowance Codes: DME Billing Limits and Bundling Rules

A4238 and A4239 are monthly supply allowances that may be billed for up to three units of service per 90-day period. Suppliers may not dispense more than a 90-day supply at one time. Claims exceeding three units within 90 days will be denied as not reasonable and necessary.

Sensors and transmitters are bundled into the supply allowance and cannot be billed separately; doing so is denied as unbundling. Standard refill requirements do not apply to A4238 or A4239; however, suppliers must still follow CMS’s specific billing and dispensing requirements for the monthly allowance.

The distinction between adjunctive and non-adjunctive matters here too. For non-adjunctive CGMs, the A4239 supply allowance already includes the home blood glucose monitor and its related supplies (test strips, lancets, calibration solutions). Medicare does not separately cover a standard home BGM and related supplies when billed in addition to an E2103/A4239 claim; that combination is denied as duplicative. Adjunctive CGMs work differently: since adjunctive devices don’t replace a standard home BGM, the BGM and its related supplies can be billed separately in addition to the A4238 supply allowance.

Also, initial Medicare CGM coverage requires the beneficiary to meet several criteria, including having diabetes, being sufficiently trained to use the prescribed CGM, and using a CGM prescribed in accordance with its FDA indications. The beneficiary must also be insulin-treated or have a documented history of problematic hypoglycemia that meets Medicare’s criteria. Within six months before ordering the CGM, the treating practitioner must conduct an in-person or Medicare-approved telehealth visit to evaluate diabetes control and confirm the applicable coverage criteria are met.

Medicare also requires documentation for continued coverage. Every six months after the initial prescription, the treating practitioner must document another in-person or Medicare-approved telehealth visit confirming the patient is adhering to their CGM regimen and diabetes treatment plan.

CG and KF Modifiers in DME Billing: Two CGM-Specific Requirements

Beyond the device and supply codes, CGM claims carry modifier requirements that don’t apply to most other DME categories:

CG modifier — signals that all applicable CGM coverage criteria in the Glucose Monitors LCD have been met. It’s added to the claim line for initial coverage when criteria 1 through 5 are satisfied, and for continued coverage when the continued-coverage criterion is met. If any coverage criterion isn’t met, the CG modifier must not be used.

KF modifier — required on claims for CGM devices and supplies classified by the FDA as Class III devices, as Class II and Class III CGMs are priced differently under the DME fee schedule.

Also, the KX or KS modifier must also be reported on every applicable CGM device and supply claim. Use KX when the beneficiary is insulin-treated and KS when the beneficiary is not insulin-treated. Using the incorrect modifier can misrepresent the coverage pathway under which the beneficiary qualifies.

How the 2028 DMEPOS Competitive Bidding Round Affects CGM Billing

CMS has finalized the next round of the DMEPOS Competitive Bidding Program, and Class II continuous glucose monitors and insulin pumps are included among the product categories, alongside urological supplies, ostomy supplies, hydrophilic urinary catheters, and several off-the-shelf brace categories. The current CMS fact sheet sets contracts and new pricing to take effect no later than January 1, 2028, with a six-month beneficiary transition period.

For CGM billing specifically, CMS has designated A4239 as the lead item for this product category, with payment potentially shifting to a monthly rental model that includes all supplies and accessories. Suppliers outside the winning contract group will need to transition affected beneficiaries or pursue grandfathered-supplier status for patients already renting equipment when the contract period begins. We cover the broader competitive bidding relaunch and its effect on other DME categories in our DMEPOS rule changes overview.

Combined with the OIG’s overpayment findings, this signals that CGM billing is heading toward tighter pricing and more coding scrutiny.

Related Reading: How to Validate HCPCS Codes Before Submitting DME Billing Claims

CGM Billing Inside a Broader DME Billing Workflow

CGM billing asks for more precision than most DME billing categories: matching the exact device to its PCL listing, applying the CG and KF modifiers correctly, keeping supply allowances within their monthly limits, and tracking a six-month documentation cycle that doesn’t exist for most other equipment types. Errors in any of these areas can result in claim denials or payment issues, independent of whether the patient actually needed the device.

SunKnowledge supports DME billing for suppliers handling CGMs and other diabetic supply categories, including eligibility verification, PCL and modifier validation, documentation tracking for periodic coverage visits, and denial management. With a dedicated account manager and resources taking care of your billing requirement, our experts rigorously ensure doctor office follow-up too, to reduce your DME billing errors. Understand the entire billing requirement, be it rental, new or used durable medical equipment; our billers ensure seamless billing operation at only $7/hour. Talk to our team about how we handle CGM billing as part of full-service DME billing support.

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