HCPCS Code A4238: Supply Allowance for Adjunctive, Non-Implanted Continuous Glucose Monitor (CGM), Includes All Supplies and Accessories

Learn what correct coding guidelines, billing rules, documentation needs, and required modifiers for CGM supplies. Read the complete guide.

Use Code

## **What is a CGM supply allowance?** HCPCS code A4238 is the supply allowance for adjunctive, non-implanted continuous glucose monitor (CGM). The full official name is "Supply allowance for adjunctive, non-implanted continuous glucose monitor (CGM), includes all supplies and accessories, 1 month supply = 1 unit of service." This code bundles all the recurring consumables needed to operate an adjunctive continuous glucose monitor. Unlike home blood glucose monitors, CGMs track interstitial glucose in real-time. An adjunctive CGM requires related BGM testing supplies to confirm readings or calibrate the device because it isn't FDA-approved to replace fingerstick testing for treatment decisions. In contrast, a non-adjunctive (or therapeutic) CGM is FDA-cleared to replace routine fingerstick testing. This is why a therapeutic continuous glucose monitor is coded differently. Under current Medicare policy, the "adjunctive" status is the key coverage and billing criterion. A4238 is used for the supplies of adjunctive CGM devices, while A4239 is used for non-adjunctive CGM devices. The vast majority of modern CGM systems on the market today (like Dexcom and FreeStyle Libre) are non-adjunctive. A4238 is now primarily used for a small, specific set of older devices or those integrated with certain insulin pumps. One unit of A4238 covers all necessary supplies and accessories for a month, including CGM sensors, transmitters, and adhesives. It does not cover test strips or home blood glucose monitors, which are billed separately when medically necessary.

## **A4238 documentation requirements** Before billing A4238, you must ensure the medical record meets durable medical equipment (DME) standards to support medical necessity and prevent claim denials. ### **Standard Written Order (SWO)** A valid SWO must be in place before supplies are dispensed. It should include the patient’s name, the diagnosis supporting diabetes treatment, the CGM receiver or device model, and the prescribing practitioner’s signature and date. ### **Device qualification** The specific CGM device must be covered as DME and listed on the PDAC Product Classification List. Suppliers should retain proof of coding verification. ### **Patient eligibility** Medical records must confirm the patient meets the criteria outlined in the Local Coverage Determination (LCD) for Glucose Monitors (L33822). This includes documentation of the patient's condition (e.g., insulin-treated diabetes) and their ability to effectively use the device. ### **Modifier justification** The record must support the use of any modifiers applied to the claim. For example, documentation must show that the patient is insulin-treated to justify the KX modifier. ### **Supply management** Suppliers should document utilization patterns to ensure that supply shipments don't exceed the patient's expected needs.

## **A4238 billing requirements** Billing for A4238 follows strict CMS and payer-specific rules to ensure proper reimbursement. ### **Units of service** A4238 can be billed in a single claim line for a 90-day supply (3 units). The "From" and "To" dates of service on the claim must be the same, reflecting a single date of service for the entire supply. ### **Bundled supplies** Do not bill CGM sensors, transmitters, or other consumables separately. All adjunctive CGM supplies are bundled into A4238. ### **Integrated systems** If a CGM is integrated with an insulin pump, the billing code for the supplies follows the FDA classification of the CGM component. The beneficiary must meet the coverage criteria for both the CGM and the insulin pump. ### **Companion device** A4238 must be paired with a covered adjunctive CGM receiver, typically coded as E2102, to qualify for Medicare reimbursement. Claims for A4238 without a covered companion device will be denied.

## **A4238 applicable modifiers** According to the Glucose Monitor Policy Article, specific modifiers must be used on claims for adjunctive CGM devices and their supplies (codes E2102 and A4238). - **KX**: Use if the patient is insulin-treated. The KX modifier is not for patients exclusively using oral hypoglycemic agents. - **KS**: Use if the patient is non-insulin-treated. - **CG**: The CG modifier is only required for A4238 claims if the adjunctive CGM device (E2102) is incorporated into an insulin infusion pump. You must apply this modifier only if the patient meets all of the coverage criteria for both the Glucose Monitors LCD and the External Infusion Pumps LCD. - **KF**: The KF modifier is required if the adjunctive CGM device (E2102) and its supplies (A4238) are classified by the FDA as a Class III device. You must use either **KX** or **KS** on every claim line, but not both.

## **Other relevant codes** - **A4239**: Supply allowance for a non-adjunctive (therapeutic) CGM. This is the code for the supplies of most modern non-adjunctive CGM devices, which are considered a therapeutic continuous glucose monitor. - **E2102**: Adjunctive, non-implanted CGM receiver. This is the companion device code for A4238. - **E2103**: Non-adjunctive (therapeutic) CGM receiver. This is the companion device code for A4239. Do not confuse the DME codes above with the non-DME codes. A9276, A9277, and A9278 are for non-DME systems and are not typically covered by Medicare. They should not be billed as an alternative to or in conjunction with A4238.

Frequently asked questions

A4238 can be billed in a single claim line for a 90-day supply (3 units). Medicare contractors (DME MACs) stress that the "From" and "To" dates of service on the claim must be the same (i.e., you bill a 90-day supply on a single date, not spanned across 90 days).

No. CGM sensors, CGM transmitters, calibration solutions, and other adjunctive CGM supplies and accessories are included in A4238 and cannot be billed separately.

When billing A4238, you must include a KX or KS modifier. Use KX if the patient is insulin-treated, or KS if the patient is not. Additionally, you must use the CG modifier if the adjunctive CGM is integrated with an insulin pump and all coverage criteria for both devices are met. Finally, a KF modifier is required if the device is classified by the FDA as a Class III device.