To get a continuous glucose monitor covered by insurance, you need three things lined up before anyone bills a claim: a prescription from your doctor, documentation showing the CGM is medically necessary for your specific situation, and, in most cases, a prior authorization approved by your insurer. Skip any one of them and the claim gets denied even on a plan that technically covers CGMs. Retail cost for CGM supplies runs roughly $160 to $500 per month, so the gap between a clean approval and a rejection is real money.
Find Out How Your Plan Classifies CGMs
Before anything else, figure out whether your plan handles CGMs as durable medical equipment or as a pharmacy benefit. The two paths work differently and use different billing codes, suppliers, and cost-sharing.
Under the DME path, you order sensors and transmitters through a medical equipment supplier, your doctor submits a prior authorization, and the insurer processes the claim as a medical benefit. You typically pay coinsurance (often 20%) after your deductible. Under the pharmacy path, your doctor writes a prescription, you pick up sensors at a retail or mail-order pharmacy, and you pay a copay per fill. The pharmacy route is generally faster; the DME channel involves prior authorizations that 93% of surveyed physicians say delay access to care.
Your plan’s Summary of Benefits and Coverage document spells out which category applies and what your cost-sharing looks like. Call the number on the back of your card and ask directly: is a CGM covered under my DME benefit or my pharmacy benefit, and do I need prior authorization? Get the answer in writing when you can. The person processing your claim months later will not remember what a phone rep told you.
Check the Eligibility Criteria Your Insurer Uses
Every private insurer sets its own rules, but they cluster around the same themes. You will almost always need a diabetes diagnosis: Type 1, insulin-dependent Type 2, or in some cases Type 2 managed with other medications. Many plans also look for a history of blood sugar that is hard to control with finger-stick testing, documented episodes of dangerously low blood sugar, or an intensive insulin regimen. Some plans still require evidence that you have been testing multiple times daily with conventional methods first.
These requirements live in the insurer’s medical policy documents, which are separate from your summary of benefits. Look on the insurer’s website for a “clinical policy bulletin” or “medical coverage policy” and search for “continuous glucose monitor.” Reading the actual policy before your doctor submits anything lets you address every requirement in one shot instead of going back and forth.
Gestational diabetes and prediabetes coverage is less predictable. Some plans cover CGMs for gestational diabetes with strong justification. Prediabetes coverage remains uncommon. If your situation sits outside the typical Type 1 or Type 2 categories, the medical necessity write-up matters even more.
Build the Medical Necessity Documentation
A prescription alone will not carry the claim. Your doctor needs to document why continuous monitoring is necessary for you specifically. Insurers want clinical evidence, not just a checked box. The prescription itself should include your diagnosis, the specific CGM model, and a clear explanation of why continuous monitoring is needed.
The strongest medical necessity packages pull several elements together:
- Blood glucose logs showing frequent highs, lows, or wide swings that finger-stick testing has not adequately captured.
- A1C results showing your diabetes is not well controlled, or that tight control has come at the cost of frequent hypoglycemia.
- A hypoglycemia history, especially episodes where you needed someone else’s help or did not recognize the symptoms until they became dangerous.
- Notes showing your doctor has already tried adjusting medications, insulin doses, or testing schedules, and those changes have not solved the problem.
- Office visit progress notes where your doctor discusses the need for continuous monitoring in the clinical assessment.
Most private plans let a primary care physician prescribe a CGM; you do not have to see an endocrinologist. If your insurer pushes back on medical necessity, though, an endocrinologist’s involvement strengthens the case. Ask your doctor to write the justification in language that mirrors the insurer’s eligibility criteria. If the policy says “history of recurrent hypoglycemia,” the documentation should use that exact phrase, backed by specific dates and glucose readings.
Submit the Prior Authorization
Most plans require prior authorization before they will pay for a CGM. Your doctor’s office typically submits the request through the insurer’s electronic portal or by fax, including your diagnosis, the prescribed CGM model, and the medical necessity documentation.
Turnaround times run from a few days to several weeks depending on the insurer and whether they come back asking for more information. If your medical situation is urgent, for example because you are having dangerous hypoglycemic episodes, your doctor can request an expedited review with a written explanation of the health risk. Once approved, prior authorizations are usually valid for six to twelve months. Put the expiration date on your calendar. A lapsed authorization means your next refill gets denied even though nothing about your medical situation changed.
Incomplete documentation is the most common reason prior authorizations stall. Before your doctor submits, walk through the insurer’s requirements together and confirm every item is in the initial package. Resubmitting after a rejection for missing paperwork can add weeks.
Confirm the Billing Codes Before the Order Goes In
Incorrect billing codes are one of the most preventable causes of CGM denials. The codes have to match how your insurer classifies the device.
For CGMs processed as DME, Medicare and many private insurers use a supply allowance system. Code A4239 covers the supply allowance for non-adjunctive CGMs (devices that can replace finger-stick testing), and A4238 covers adjunctive CGMs (devices used alongside finger-stick testing). Each allowance code bundles sensors, transmitters, and related supplies into a single code, so suppliers should not bill those pieces separately.1CGS Administrators LLC. Continuous Glucose Monitors CGMs Supply Allowance Billing Reminder The receiver or monitor itself is billed separately under E2103 (non-adjunctive) or E2102 (adjunctive).2Centers for Medicare and Medicaid Services. Glucose Monitor – Policy Article A52464
If your CGM does not qualify as DME under your plan, different codes apply: A9276 for sensors, A9277 for transmitters, and A9278 for receivers. Using DME codes on a pharmacy claim, or the reverse, almost guarantees a denial. Your supplier or pharmacist handles the coding, but confirm with your insurer which codes they expect for your plan and CGM model, and pass that along to whoever fills the order.
Medicare Coverage for CGMs
Medicare covers CGMs under Part B as durable medical equipment. After you meet the Part B deductible, you pay 20% of the Medicare-approved amount and Medicare pays 80%. Supplies must come from a Medicare-enrolled DME supplier; pharmacy pickup is not available under traditional Medicare for CGMs classified as DME.3Medicare.gov. Continuous Glucose Monitors
Medicare’s eligibility criteria changed in April 2023. The old rule requiring four daily finger sticks and three or more daily insulin injections is gone. Under current rules, you qualify if you have diabetes and meet one of two pathways: you are being treated with insulin at any frequency, or you have a documented history of problematic hypoglycemia even without insulin treatment.4Centers for Medicare and Medicaid Services. Glucose Monitoring Supplies
For the hypoglycemia pathway, your doctor must document either more than one Level 2 episode (glucose below 54 mg/dL) that persisted despite medication adjustments, or at least one Level 3 episode where your blood sugar dropped below 54 mg/dL and you needed someone else’s help to treat it.2Centers for Medicare and Medicaid Services. Glucose Monitor – Policy Article A52464
Before the initial order, your treating provider must see you in person or through a Medicare-approved telehealth visit within the prior six months to evaluate your control and confirm you meet the criteria. Every six months after that, another visit is required to document that you are still using the CGM and that the supplies remain medically necessary. Missing that six-month visit is one of the most common reasons Medicare CGM claims get flagged.4Centers for Medicare and Medicaid Services. Glucose Monitoring Supplies
Medicaid also covers CGMs in most states (over 45 states plus the District of Columbia provide some level of coverage), but the eligibility rules, covered devices, and approval steps vary by state. Check with your state Medicaid office directly.
What to Do If Your CGM Claim Is Denied
Denials happen even with solid documentation. Your insurer’s Explanation of Benefits identifies the specific reason, and the reason dictates your response. The most common causes are insufficient medical necessity documentation, incorrect billing codes, using an out-of-network supplier, or not meeting the plan’s eligibility criteria.
If the denial is a paperwork problem (wrong code, missing labs, expired prior authorization), a corrected resubmission often resolves it without a formal appeal. Call the insurer first to confirm exactly what is missing, then fix everything in one submission.
If the insurer says the CGM is not medically necessary, the response needs to come from your doctor. A letter that directly addresses the stated reason for denial, with specific clinical evidence attached, carries real weight. Many insurers offer a peer-to-peer review at this stage, where your doctor speaks with the insurance company’s medical reviewer to make the case. That conversation can be highly effective because it lets your doctor answer the reviewer’s specific concerns in real time.
Keep a written log of every call, email, and document throughout this process, with dates and representative names. If the dispute escalates, that record becomes essential.
Internal Appeal
During an internal appeal, a different person at the insurance company (not the one who issued the denial) reviews your claim from scratch. Include your doctor’s letter of medical necessity, all supporting clinical records, and a written explanation of why the denial was wrong, point by point. Most plans require you to file within 180 days of the denial notice, though some set shorter windows. Check the exact deadline on your denial letter and do not cut it close.
External Review
If the internal appeal fails, federal law gives you the right to an external review for any denial involving medical judgment, including medical necessity determinations. You have four months from the final internal denial to request one.5eCFR. 45 CFR 147.136 – Internal Claims and Appeals and External Review Processes The plan must assign your case to an independent review organization accredited by a national body like URAC. That reviewer has no connection to your insurance company, and the decision is binding: if the reviewer determines the CGM is medically necessary, your insurer must cover it. Your state insurance department can help if you get stuck.
Cutting What You Pay After Coverage Kicks In
Even with insurance, copays and coinsurance add up. Both major CGM manufacturers run programs that can bring costs down.
Abbott, which makes the FreeStyle Libre system, reports that most patients with private insurance pay between $0 and $20 per sensor fill. If your plan’s cost-sharing would charge more than $75 for two sensors, Abbott’s copay card program can reduce what you pay. Getting a prior authorization can save privately insured patients over 50% per month on Libre sensors.6Abbott (FreeStyle Libre). Private Insurance Coverage for FreeStyle Libre Systems
Dexcom offers a pharmacy savings program that takes more than $210 off each 30-day sensor supply and over $200 off a Dexcom receiver at retail, usable up to 12 times per year. The catch: you have to opt out of insurance coverage or other copay assistance to use it, so the coupon is designed for people who are uninsured or whose insurance does not cover Dexcom. Dexcom also runs a separate patient assistance program with income-based discounts.7Dexcom. Dexcom CGM Cost Savings and Coupons Medicare beneficiaries generally cannot use manufacturer copay cards due to federal anti-kickback rules.
CGM sensors, transmitters, and receivers qualify as medical expenses payable with HSA or FSA funds. The IRS treats diagnostic devices for monitoring and treating illness as eligible, and specifically uses diabetes blood sugar testing as an example.8Internal Revenue Service. Publication 502 – Medical and Dental Expenses The IRS has further clarified that CGMs for individuals diagnosed with diabetes are generally treated as preventive care for high-deductible health plans, so your HDHP can cover CGM costs before you meet your deductible without disqualifying you from HSA contributions.9Internal Revenue Service. Publication 969 – Health Savings Accounts and Other Tax-Favored Health Plans One tax detail worth remembering: if you pay for CGM supplies with tax-free HSA or FSA distributions, you cannot also claim those same expenses as an itemized medical deduction.