You choose the drug. What happens next is decided by which of 328 Medicare Part D formularies your patient happens to be enrolled in — and nothing in the exam room tells you which one.
The clinical decision is finished. You picked the drug. Everything after that — the prior authorization, the step therapy, the quantity limit, the appeal, the assistance application, the specialty pharmacy routing — is the part a company just got valued at $3B to automate.
Here is the first step of that path, for real, from the file CMS publishes every quarter. Each square below is one of the 328 Medicare Part D formularies operating in 2026. Pick a drug and watch what the country decides about it.
Read the colours again. The green squares and the dark red squares are the same drug, at the same dose, for the same indication, in the same country, in the same month. The only variable is which envelope the patient’s Part D card came in.
The friction was never one gate. It was fifty, and the only people who can see all fifty are the ones who live inside them.
Try phenobarbital — a drug older than the FDA. 131 plans wave it through, 40 cap the quantity, 79 want a prior auth, 78 want a prior auth and something else. Try methotrexate: 239 plans require a prior authorization on its own, and 54 stack more on top. Try levothyroxine, where 326 of 328 plans agree it’s free, and notice how rare that is.
Across the whole file, 49.5% of the 1,124,586 drug–formulary listings in Part D 2026 carry at least one gate. Of the 4,196 individual drug products listed on 50 or more formularies, 2,056 are split — some plans require a prior auth, some don’t. Only 212 are gated everywhere. 430 sit in a 25–75% band where the prescriber is functionally flipping a coin.
On October 1 UnitedHealthcare drops prior authorization from roughly 1,700 service codes — the largest single-payer cut of the year. Look at the grid and ask what that does to it. It removes one colour from some squares. The variance stays. That’s why the $3B doesn’t evaporate: the product isn’t “beat the gate,” it’s “know which gate.” If you’re building here, the defensible unit is a named step on a named formulary, not a category.