Semaglutide cost Medicare $9.67 billion in 2023. Three years earlier, it cost $1.2 billion. That's not a trend line. It's a vertical wall.

The drug entered the Medicare Part D data in 2018 with 23,164 claims and a total cost of $21 million. By 2023, claims had reached 7.17 million and spending had crossed $9.67 billion. No drug in the program's recent history has added dollars to the federal ledger at this pace, and the trajectory shows no sign of flattening.

The Only Useful Comparison Is Sofosbuvir, and Semaglutide Already Beat It

When hepatitis C drugs arrived in Medicare around 2013, they triggered a genuine budget emergency. Sofosbuvir peaked at $6.7 billion in 2015 across 218,785 claims. Congress held hearings. Insurers rationed access. The crisis eventually resolved as prices fell and the treatable population shrank.

Semaglutide hit $9.67 billion in 2023 across 7.17 million claims. That's 44% more spending than sofosbuvir's peak, spread across 33 times as many claims. The sofosbuvir episode was a price shock. Semaglutide is a volume shock, and the treatable population is not shrinking. Roughly 40% of American adults have obesity. The eligible pool for GLP-1 therapy in Medicare is orders of magnitude larger than the hepatitis C population ever was.

The cost-per-claim figure makes this dynamic explicit. Semaglutide's per-claim cost actually fell 0.75% from 2022 to 2023, from $1,358.74 to $1,348.56. Spending nearly doubled anyway, because claims volume grew from 3.43 million to 7.17 million in a single year. Price is not the driver here. Bodies are.

Primary Care Absorbed the Prescribing Load

When semaglutide first appeared in Medicare data, endocrinologists dominated its prescribing. In 2019, endocrinology accounted for 30.42% of semaglutide total drug cost. By 2020, that share had dropped to 28.26%, while Family Practice's share rose from 19.4% to 21.04% over the same period. Nurse Practitioners moved from 16.66% to 17.66%.

This shift matters for understanding the spending trajectory. Endocrinologists manage a finite, referral-dependent patient population. Primary care and nurse practitioners do not. As prescribing authority diffused outward from specialists, the ceiling on potential volume rose with it. The number of prescribers writing semaglutide grew from 27,680 in 2020 to 136,488 in 2023, nearly a fivefold increase in three years.

That prescriber expansion is the structural engine behind the volume numbers. Each new prescriber brings their own panel of eligible patients. At 136,488 active prescribers and a cost-per-claim of $1,348.56, even modest growth in average claims per prescriber translates to billions in additional program spending.

Liraglutide's Collapse Shows What Displacement Looks Like

Liraglutide, the older GLP-1 that preceded semaglutide's dominance, peaked at 1.12 million claims in 2018 and $1.19 billion in total cost. By 2023, claims had fallen to 425,747 and cost had dropped to $617 million. Semaglutide didn't just grow. It absorbed the existing GLP-1 market and then expanded it by a factor that made the original market look trivial.

The combined GLP-1 spending picture in 2023: semaglutide at $9.67 billion, liraglutide at $617 million. Semaglutide alone now represents more than 15 times liraglutide's current spend. For Medicare, the practical consequence is that the program is now structurally exposed to a single molecule in a way that has no recent precedent. Sofosbuvir's peak was a one-time event tied to a curable disease. Semaglutide treats a chronic condition requiring indefinite therapy.

Cost-per-claim fell 0.75% in 2023 while total spending grew by more than $5 billion. If volume continues doubling annually and per-claim costs hold flat or decline modestly, the $9.67 billion figure from 2023 is not a ceiling. It's a floor.