Washington D.C. spent $5.21 per day of drug supply under Medicare Part D in 2023. In the lowest-cost state group, that same metric was $0.76 for the most common drug in their top 10. That's not a rounding error or a data artifact. It's a window into how dramatically a single federal program can fracture across geography.

DC's Cost Per Day Has Nearly Doubled in a Decade

In 2013, D.C. led all states at $2.82 per day of drug supply. By 2023, that figure had risen to $5.21, an 85% increase over ten years. New York ranked second in 2023 at $3.92 per day, and Texas, at the lower end of the distribution shown, came in at $2.95.

The gap between D.C. and Texas alone is 77 cents versus $5.21, a spread that has widened considerably since 2013, when D.C.'s $2.82 compared to West Virginia's $1.74. The top-to-bottom range has grown, not shrunk. For a program designed to provide uniform drug coverage to Medicare beneficiaries, that divergence carries real consequences: federal dollars are buying very different amounts of drug supply depending on where a patient lives.

Drug Mix Explains Some of the Gap, But Not All of It

Compare the top 10 drugs by total cost in the five highest-cost states (Alaska, Connecticut, D.C., New York, and the U.S. Virgin Islands) against the five lowest-cost states (Guam, Montana, North Dakota, Puerto Rico, and Wyoming), and a structural difference emerges.

Levothyroxine Sodium, a generic thyroid medication with a cost of just $0.76 per day and nearly 1.7 million claims, appears only in the low-cost group's top 10. High-volume, low-cost generics like that pull the average down considerably. The high-cost group's top 10 is dominated by specialty and brand-name drugs: Semaglutide at $32.86 per day, Lenalidomide at $601.26 per day, and Adalimumab at $297.53 per day.

For the drugs that appear in both groups, the per-day cost differences are modest. Semaglutide costs $32.86 per day in high-cost states and $32.83 in low-cost states. Lenalidomide actually costs more per day in the low-cost group ($648.35 vs. $601.26). The divergence in overall cost-per-day isn't primarily about paying more for the same pills. It's about which pills are being prescribed.

What the Drug Mix Difference Costs Taxpayers

High-cost states are filling their top-10 drug lists with expensive specialty medications at high volumes. Semaglutide alone generated $924 million in total drug costs across the high-cost state group, compared to $84 million in the low-cost group. That's a more than 10-to-1 ratio in total spending on a drug that costs nearly the same per day in both groups. The difference is volume and prescribing patterns, not unit price.

D.C.'s $454 million in total drug costs came from just 1.6 million claims, a relatively small claims volume that still produced a per-day cost of $5.21. That ratio reflects a patient population receiving expensive therapies at high intensity, not simply a large number of routine prescriptions.

For Medicare's budget, the practical implication is that geographic variation in Part D spending is increasingly a function of what gets prescribed, not just what drugs cost. A beneficiary in Montana filling a thyroid prescription and a beneficiary in D.C. filling a specialty HIV or cancer regimen are both covered under the same program, but the federal cost per day of their drug supply differs by a factor of nearly seven. Whether D.C.'s cost trajectory continues at its current pace, and whether lower-cost states are beginning to see similar specialty drug adoption, will determine how much wider that gap gets by 2033.