Public coverage of these drugs is usually described as a yes or a no, and it is neither. The governing text does not name a molecule; it names a use. Everything that follows from it — who is covered, who is not, and why the answer changes at a state line — comes from that single drafting choice, which was made long before any of these products existed. The difference between the two approvals each molecule carries is set out in the article on the two indications.
What the exclusion actually says
The statutory definition of a covered Part D drug excludes the drugs and uses that Medicaid may exclude under section 1927(d)(2) of the Social Security Act. That list includes, in the statute’s words, “[a]gents when used for anorexia, weight loss, or weight gain.”[1]
One word does the heavy lifting. Because the items in section 1927(d)(2) may be excluded under Medicaid, state Medicaid programs have discretion over whether to provide the coverage, whereas Medicare does not.[1] The same sentence therefore produces a federal prohibition on one side and fifty separate decisions on the other.
CMS has read that phrase the same way since the Part D program began in 2006: a drug when used for weight loss, even when not used cosmetically, is outside the definition of a covered Part D drug, regardless of whether the use treats obesity. Such drugs can be carried by a Part D plan only as a supplemental benefit.[1]
The exception that already exists
The exclusion attaches to a use, so it releases the moment the use changes. CMS issued guidance in March 2024 confirming that a weight medication which receives approval for an indication other than chronic weight management can be a Part D drug for that specific use. Under that policy these products are coverable for glycemic control in type 2 diabetes, for reducing major adverse cardiovascular events in adults with type 2 diabetes and established cardiovascular disease, and for reducing those events in non-diabetic adults with established cardiovascular disease and obesity or overweight.[1]
The formulary data show what that means in practice. An analysis of quarterly CMS Basic Drugs Formulary File data from 2020 quarter two through 2024 quarter three, covering 54,358 Medicare Advantage prescription drug plan and 15,895 standalone plan quarter-plan observations, found coverage of injectable semaglutide has remained above 90% since 2021, with tirzepatide rising from 26.5% in 2022 quarter three to 92.9% by 2024 quarter three and oral semaglutide from 40.3% to 91.8%.[5]
So the molecule is on nearly every Medicare formulary and the indication is barred. A beneficiary with obesity and established cardiovascular disease may have a covered path that a beneficiary with obesity alone does not, and the trial behind that indication is described in the SELECT write-up.
What changed, and when it stopped changing
On December 10, 2024, CMS published a proposed rule reinterpreting the phrase “agents when used for . . . weight loss” so that it would no longer capture anti-obesity medications used to treat obesity. The reasoning was that the longstanding reading reflected an outdated medical understanding, given that obesity is now widely regarded as a chronic disease.[1]
The proposal drew a line that is easy to miss. CMS expressly did not propose to permit coverage for people with overweight, even with weight-related comorbid conditions, on the stated basis that “unlike obesity, overweight is not recognized as a disease.”[1] A reader at a body-mass index of 28 with hypertension sat outside even the expanded version.
The final rule, published April 15, 2025, closed the question. It states: “We also do not intend to finalize the following provisions from the proposed rule: . . . Part D Coverage of Anti-Obesity Medications (AOMs) and Application to the Medicaid Program”.[2] The reinterpretation was never adopted, and the exclusion stands as it has since 2006.
The same sentence has been read two ways for decades
The statutory phrase covers weight loss and weight gain in one breath, and CMS has never applied the two halves alike. Its longstanding reading of “agents when used for . . . weight gain” has not included drugs used to treat acquired immunodeficiency syndrome wasting and cachexia, a position Part D inherited from a Medicaid policy effective April 5, 1999.[1] A drug given to add weight for a recognized disease was never treated as an excluded agent; a drug given to remove it was.
That asymmetry is what the 2024 proposal was framed as correcting. CMS wrote that it believed its reading of the weight-gain clause was correct, and that adjusting the weight-loss clause would bring the two interpretations into alignment.[1] The alignment was not adopted, which leaves one sentence carrying two different rules depending on which direction the weight moves.
Who the exclusion now applies to
The population behind the argument has changed more than the rule has. CMS data cited in the proposed rule indicate approximately 22% of all Medicare beneficiaries had a diagnosis of obesity in 2022, against 8.7% in 2012.[1] The agency also cautions that claims-based prevalence understates the real figure, since it depends on obesity being recorded as a diagnosis code, and notes that National Health and Nutrition Examination Survey data for 2017 to March 2020 put obesity prevalence in the United States population aged 60 and over at 41.5%.[1]
A rule written in 2003 for a small category of drugs now governs a condition documented in roughly a fifth of the program and present in something closer to two fifths of the age band. What that age group specifically knows and does not know about these drugs is covered in the older-adults article.
The money argument behind the decision
The fiscal case has been modeled. An economic evaluation published in 2025 projected the ten-year impact of expanded Medicare coverage across 2026 to 2035 using a validated microsimulation, with a base case of 10% one-time uptake among eligible adults, 40% adherence beyond the first year, and a further 10% price discount. Among 30 million cumulative eligible beneficiaries, it estimated 3 million would be treated, drug costs of $65.9 billion, healthcare cost offsets of $18.2 billion, and net increased spending of $47.7 billion.[6]
The sensitivity analysis is the part that matters for anyone expecting coverage to arrive on its own. Higher uptake and adherence produced larger health savings, but those savings remained smaller than the additional drug spending in every scenario tested. Even a moderate case of 5% uptake, 20% adherence and a 30% additional discount still reached $8 billion in net spending over a decade.[6]
The 2026 route around the statute
Rather than change the reading, CMS built a voluntary demonstration. The BALANCE Model, run through the Center for Medicare and Medicaid Innovation, expands coverage of these medications for obesity in Medicaid and, as designed, in Medicare Part D. CMS states that “participation in BALANCE is voluntary for manufacturers, state Medicaid agencies, and Part D plans”, with state Medicaid agencies able to join beginning in May 2026 through January 1, 2027, and coverage subject to negotiated patient eligibility criteria and prior authorization.[3]
The Part D half did not happen. CMS states that the model will not launch in Medicare Part D in 2027, and that the temporary Medicare GLP-1 Bridge has been extended through December 31, 2027 instead.[3] Voluntary means what it says: a demonstration that plans decline to join does not start. The durable lesson is that an announced program and an available benefit are separated by a participation decision nobody publicizes.
Medicaid: mandatory for one use, optional for another
State Medicaid programs must cover nearly all approved drugs from participating manufacturers, so coverage of these products is required for diabetes, and became required for cardiovascular disease in March 2024 and for moderate to severe obstructive sleep apnea in adults with obesity in December 2024, as those indications were approved. Coverage is also required where medically necessary for children under the Early and Periodic Screening, Diagnostic and Treatment benefit.[4]
Obesity is the optional column, and it has been shrinking. Thirteen state Medicaid programs covered these drugs for obesity treatment under fee-for-service as of January 2026. The KFF 50-State Medicaid Budget Survey, conducted by Health Management Associates in November 2025, had found sixteen as of October 2025; California, New Hampshire, Pennsylvania and South Carolina eliminated coverage in the interval, and North Carolina dropped coverage in October 2025 and reinstated it in December.[4]
Spending explains the direction. Medicaid gross spending on this class rose from roughly $1 billion across about 1 million prescriptions in 2019 to roughly $9 billion across more than 8 million prescriptions in 2024, moving from 1% to over 8% of all Medicaid prescription drug spending before rebates.[4] The sleep-apnea indication that became mandatory in the middle of that is covered in the sleep-apnea article.
What state variation looks like in the claims
A cross-sectional analysis of pharmacy claims from the Komodo Healthcare Map for January through December 2023, compared against 2022 to 2023 Behavioral Risk Factor Surveillance System prevalence, found that utilization for diabetes tracked diabetes prevalence strongly in the commercially insured population, moderately in Medicare and weakly in Medicaid. For obesity, utilization showed only weak or negligible correlation with obesity prevalence anywhere, while use in states with restricted or unrestricted Medicaid coverage was nominally higher than in states with no coverage.[7]
That is the shape worth carrying: in this class, where a person lives predicts access better than how much they need it. Because these policies move on state budget cycles, the only reliable answer is the current preferred drug list and prior-authorization criteria of the state’s own program, not any national count including the one above.
What none of this settles
No statement here describes a particular beneficiary’s coverage. Part D plans differ in what they carry as supplemental benefits, Medicaid programs differ by state and change within a plan year, and the demonstration described above depends on which manufacturers, states and plans elected to join. A denial under these rules can still be appealed, and the levels and deadlines are in the appeals article.
Where no public benefit reaches, the purchase moves to cash, and most of that market dispenses compounded preparations, which are not FDA-approved and are not reviewed by the agency for safety, effectiveness or quality before dispensing. Manufacturer programs sit between the two and set their own terms, recorded in the savings-card article, and what the cash sellers publish is in the seller write-ups.