What is a Letter of Medical Necessity and why does it matter?

A Letter of Medical Necessity (LMN) is a formal document from your prescribing physician explaining why a CGM is medically required for your care. It should reference your diagnosis, current treatment, glucose history, and relevant clinical guidelines. A strong, detailed LMN significantly increases your chances of approval.

Can I get a CGM covered under Medicare?

Yes. Medicare covers therapeutic CGMs (like the Dexcom G6/G7 and Libre 2/3) under Part B as durable medical equipment for patients with diabetes who use insulin. You must have a prescription from a Medicare-enrolled provider and meet clinical criteria. A separate PA may or may not be required depending on your plan.

What should I do if my CGM prior authorization is denied?

File an appeal right away. Start with an internal appeal and request a peer-to-peer review between your doctor and the insurer's medical director. Submit additional supporting documentation such as glucose logs. If the internal appeal fails, you can request an external independent review through your state's insurance department.

Can I use my FSA or HSA to buy CGM supplies while waiting for authorization?

Yes. CGM devices, sensors, and related supplies are FSA and HSA eligible expenses. If you need supplies during the authorization process, mdsdiabetes.com accepts FSA and HSA payment, so you can stay stocked without waiting for insurance approval.

How to Get Prior Authorization for a CGM

Key takeaways

✓Knowing your insurer's exact eligibility criteria before applying dramatically reduces denial rates
✓A strong Letter of Medical Necessity from your doctor is the single most important document in the PA process
✓A denial can be successfully appealed — peer-to-peer reviews between your doctor and insurer are especially effective

Why Prior Authorization for CGM Is Often Required

Continuous Glucose Monitors (CGMs) have transformed diabetes management, offering real-time glucose readings without constant finger sticks. However, most insurance plans — including Medicare, Medicaid, and private insurers — require prior authorization (PA) before they'll cover CGM devices and supplies. Without approval, you could face the full out-of-pocket cost, which can run hundreds of dollars per month.

Understanding the prior authorization process empowers you to advocate for yourself and avoid costly delays in getting the technology you need.

Step 1: Confirm Your Eligibility Requirements

Before submitting a PA request, review your insurer's specific criteria. Most plans require you to meet certain conditions, which commonly include:

A confirmed diagnosis of Type 1 or Type 2 diabetes
Current use of insulin (multiple daily injections or an insulin pump)
A history of hypoglycemia unawareness or frequent low blood sugar episodes
Documentation of inadequate glucose control despite standard monitoring

Medicare, for example, covers CGMs under the durable medical equipment (DME) benefit for patients using insulin. Check your plan's Evidence of Coverage document or call member services to get the exact criteria in writing.

Step 2: Work Closely With Your Prescribing Physician

Your doctor's office is your most important partner in the PA process. Ask them to:

Write a Letter of Medical Necessity (LMN) that specifically addresses your insurer's criteria
Include your diagnosis codes (ICD-10), current medication list, and recent A1C or glucose logs
Reference clinical guidelines from the American Diabetes Association (ADA) or American Association of Clinical Endocrinology (AACE) to support the request
Submit the PA request promptly — delays on the provider side are one of the most common bottlenecks

Step 3: Submit the Prior Authorization Request

The PA request is typically submitted by your provider directly to your insurer. However, knowing what's happening at each stage helps you follow up effectively. Make sure the submission includes:

The specific CGM device and sensor HCPCS billing codes (e.g., A9278 for sensors, E2103 for CGM devices)
Supporting clinical documentation such as lab results and visit notes
The prescribing physician's NPI number and contact information

Keep a copy of everything submitted. Insurers can and do lose paperwork.

Step 4: Follow Up and Track Your Case

Most insurers are required to respond to PA requests within 14 days (or 72 hours for urgent requests). Call your insurer every few days to check the status. Note the date, time, and name of every representative you speak with. If the timeline passes without a decision, escalate to your insurer's member advocate line.

Step 5: If You're Denied, Appeal Immediately

A denial is not the end of the road. You have the right to appeal. Common and effective strategies include:

Requesting a peer-to-peer review between your doctor and the insurer's medical reviewer
Submitting additional documentation such as glucose logs showing dangerous fluctuations
Filing an external appeal through your state's insurance commissioner if internal appeals fail
Asking your doctor's office about patient assistance programs from CGM manufacturers

Getting Your CGM Supplies While You Wait

Prior authorization can take days or even weeks. If you need supplies in the meantime, mdsdiabetes.com offers a wide selection of CGM supplies, sensors, and diabetes essentials at competitive prices — with options for FSA and HSA payment. Stocking up through MDS Diabetes ensures you're never caught without the tools you need to manage your health safely.

Tips to Speed Up the Process

Ask your doctor's office if they have a dedicated PA coordinator
Use your insurer's online portal to track the request in real time
Call both your insurer and your doctor's office weekly until resolved
Keep detailed notes of every interaction in case you need to appeal

References & Sources

Frequently asked questions

Most insurers are required to respond within 14 calendar days for standard requests and 72 hours for urgent requests. In practice, the process often takes 5–10 business days if all documentation is submitted correctly the first time.

Editorial note

This article is for educational purposes only and does not constitute medical advice. Always consult your healthcare provider before making changes to your diabetes management. Last reviewed: July 12, 2026 by the MDS Diabetes editorial team.

What to do next

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How to Get Prior Authorization for CGM from Your Insurer