Prescribing a continuous glucose monitor involves more than selecting a device. You need to confirm your patient meets coverage criteria, choose the right fulfillment channel, document medical necessity, and in many cases navigate prior authorization. The specifics vary by payer and device, but the core workflow follows a predictable pattern once you know the key steps.
Who Qualifies for a CGM
Coverage criteria differ between Medicare and commercial insurers, but they overlap significantly. Medicare covers CGMs for patients who meet at least one of two conditions: they are insulin-treated, or they have a documented history of problematic hypoglycemia. For the hypoglycemia pathway, the patient must have either recurrent level 2 hypoglycemic events (glucose below 54 mg/dL) that persist despite multiple medication adjustments, or at least one level 3 event where altered mental or physical status required third-party assistance.
Private insurers often set a higher bar. A representative prior authorization form from a major managed care plan asks whether the patient requires three or more daily insulin injections or uses an insulin pump, whether they experience frequent severe hypoglycemia or hypoglycemic unawareness, or whether their A1c is 7% or above. Many commercial plans also require documentation that the patient or caregiver has received diabetes education on using a CGM and will share device readings with the prescriber. Check the specific plan’s formulary before assuming coverage, since some plans designate a preferred CGM brand and require clinical rationale if you prescribe a non-formulary device.
Documentation That Supports Medical Necessity
For Medicare beneficiaries, a face-to-face encounter must occur within six months before the CGM is ordered. This can be an in-person visit or a Medicare-approved telehealth visit. During that encounter, your chart notes should document the patient’s current diabetes management, why a CGM is medically necessary, and how the patient meets the coverage criteria listed above. A Written Order Prior to Delivery (WOPD) is also required under CMS Final Rule 1713 for CGM-related supply codes.
After the initial order, Medicare requires a follow-up visit every six months. At each visit, you need to document the patient’s adherence to the CGM regimen, review their diabetes treatment plan, and confirm that CGM supplies remain medically necessary. Gaps in this documentation are one of the most common reasons for claim denials.
For ICD-10 coding, both Type 1 (E10 series) and Type 2 (E11 series) diabetes codes support medical necessity. The specific code should reflect the patient’s clinical picture: E10.9 or E11.9 for uncomplicated diabetes, E10.65 or E11.65 for hyperglycemia, and complication-specific codes when relevant (nephropathy, retinopathy, neuropathy). Pre-existing diabetes in pregnancy is also covered under the O24 series.
Choosing the Device and Writing the Prescription
Three main CGM systems are currently available, and each has slightly different prescription components.
For the Dexcom G7, your e-prescribing order includes two line items. The first is the Dexcom G7 15-Day CGM Sensor: prescribe 3 boxes (one sensor per box) for a 30-day supply with 3 refills. The second is the Dexcom G7 Receiver, which is optional since most patients use a smartphone app. If needed, prescribe 1 receiver with a 1-year refill for commercial patients. When entering the order, select “G7” specifically in your e-prescribe module.
For the FreeStyle Libre 3 Plus or 2 Plus, prescribe 2 sensors for a 30-day supply filled monthly, with refills set to PRN or 12 additional refills for a one-year supply. A separate reader device is available but, like the Dexcom receiver, most patients use their phone instead.
The Eversense 365 is an implantable CGM with a different workflow entirely. Rather than e-prescribing to a pharmacy, you refer the patient to the manufacturer (Senseonics) through a platform like Parachute Health or by faxing an order form along with medical necessity documentation, chart notes, and insurance information. An Eversense representative then confirms eligibility, locates a trained inserter near the patient, and coordinates shipping the sensor to that inserter’s office. The patient undergoes a brief in-office procedure where a small incision is made in the upper arm to place the sensor, which then lasts up to a year.
Pharmacy vs. DME Fulfillment
Where the prescription gets filled depends on the patient’s insurance. Some plans cover CGMs as a pharmacy benefit, meaning you send the prescription to a retail or mail-order pharmacy just like any other medication. Others classify CGMs as durable medical equipment, which routes the order through a DME supplier instead.
The practical difference matters. When a CGM goes through a DME channel, a representative from the DME company typically contacts the patient to discuss copay details and shipping logistics. If the patient consents, the device and supplies ship directly to their home. This process can take longer than a pharmacy fill, so setting patient expectations upfront helps. When the CGM is covered as a pharmacy benefit, the turnaround is usually faster, and patients can often pick up sensors at their local pharmacy.
If you’re unsure which channel applies, your office staff can verify the patient’s benefits before submitting the order. Sending the prescription to the wrong channel is a common source of delays.
Navigating Prior Authorization
Most commercial insurers require prior authorization for CGMs. The clinical data points requested are fairly consistent across plans: confirmed diagnosis of Type 1 or Type 2 diabetes, current insulin regimen (number of daily injections or pump use), history of hypoglycemia or elevated A1c, and evidence that the patient has been trained on CGM use. Some plans also ask whether the patient will share CGM data with the prescribing provider.
Have the following ready before submitting:
- Recent A1c result, especially if it is 7% or above
- Current medication list showing insulin type, dose, and frequency
- Hypoglycemia documentation if applicable, including dates, glucose values, and any ER visits or third-party assistance
- Chart notes from the qualifying visit showing the clinical rationale for CGM therapy
- Diabetes education records confirming the patient knows how to use the device
If you’re prescribing a non-formulary device, you will likely need to provide a separate clinical rationale explaining why the preferred device is not appropriate for this patient. Quantity limit exceptions, such as replacements for lost or damaged sensors, also require supporting documentation.
After the Prescription Is Placed
Once the patient has their CGM, the prescribing work shifts to ongoing management. For Medicare patients, the every-six-month visit requirement is non-negotiable for continued coverage. Use these visits to review time-in-range data, adjust medications based on CGM trends, and document that the patient is actively using the device. If a patient stops wearing their CGM regularly, continued supply orders may not meet the medical necessity threshold at audit.
For patients on commercial insurance, renewal timelines vary by plan, but keeping consistent follow-up documentation protects against retroactive denials. Building CGM data review into routine diabetes visits, rather than treating it as a separate administrative task, makes the documentation burden more manageable over time.