How to appeal a CGM denial (Dexcom, FreeStyle Libre)

Original Medicare covers CGMs under Part B as durable medical equipment. The rules are in a local coverage determination, LCD L33822, Glucose Monitors. As written in November 2026, you must:

• Have diabetes.
• Have enough training to use the CGM, shown by your doctor's prescription.
• Use a CGM prescribed according to its FDA indications.
• Be treated with insulin, or have a history of problematic hypoglycemia.
• Have an in-person or Medicare-approved telehealth visit within six months before the order.

Problematic hypoglycemia means more than one level 2 low (below 54 mg/dL) that continues despite more than one change to your treatment, or one level 3 low that needed someone else's help. To keep coverage, you need a visit every six months that documents you are using the CGM.

Medicare once required people to test with fingersticks four or more times a day before it would pay for a CGM. The LCD removed that requirement effective July 18, 2021.

Effective April 16, 2023, Medicare rewrote the CGM criteria and dropped the rule that you take insulin three or more times a day or use a pump, so any insulin use now qualifies. The same revision added the problematic-hypoglycemia route for people who do not use insulin.

If a denial cites an older rule, point to the current LCD in your appeal.

Not every CGM denial is about your health history. Check for these before you appeal:

• The supplier is not enrolled. Medicare tells you to make sure your doctors and DME suppliers are enrolled in Medicare.
• Sensors were billed too far ahead. The LCD says billing more than three months of supplies at a time will be denied.
• A follow-up visit is missing. Coverage continues only with the six-month visit described above.
• A coding or billing mistake. Ask the supplier to check the codes and resubmit. See billing and coding errors.

Private plans differ. One insurer's policy, effective October 2026, says CGMs may be covered under the medical or the pharmacy benefit and refers members to their plan document. Its criteria tie coverage to insulin use, such as multiple daily injections, long-acting insulin or a pump.

This matters for denials. A claim rejected at the pharmacy may be covered through a medical-equipment supplier, or the reverse. Before you appeal, call the plan and ask which benefit covers your CGM, whether prior authorization is needed, and which suppliers to use. Abbott publishes a list of questions to ask your insurer.

A denial that says criteria were not met calls for records. Ask your doctor's office to send:

• The diabetes diagnosis code.
• Your insulin prescriptions and pharmacy fill history, if you use insulin.
• Glucose logs or meter downloads showing each low below 54 mg/dL, with dates.
• Notes showing the medicine changes made after those lows.
• The visit note from the last six months that evaluates your diabetes control.
• For continued coverage, the six-month follow-up note on how you use the CGM.

For a private plan, also ask for a free copy of the criteria the plan used, and answer each one.

With Original Medicare, start with the Medicare Summary Notice. You must file your appeal by the date in the MSN. See Original Medicare appeals, or Medicare Advantage appeals if you are in a private Medicare plan.

With a private plan, file the internal appeal within 180 days. Denials that involve medical judgment can go to external review if the plan says no again. You have 4 months after the final denial to ask, and the insurer must accept the reviewer's decision.

Whichever route you use, send the appeal in writing, keep copies, and include the denial notice, your doctor's letter tying your records to each criterion, and the supporting logs and notes.

If you have type 2 diabetes, do not use insulin and have no record of problem lows, Medicare's criteria are not met, and an appeal has little to point to. Ask your doctor whether your history includes lows that were never written down.

Over-the-counter CGMs exist. On March 5, 2024, the FDA cleared the first one, intended for adults who do not use insulin. The FDA said it is not for people with problematic hypoglycemia.

The manufacturers offer coverage help: Dexcom offers a free benefits check, and Abbott has an insurance guide for FreeStyle Libre.