PBM stands for pharmacy benefit manager, a type of company that acts as a middleman between health insurers, drug manufacturers, and pharmacies. PBMs decide which prescription drugs your insurance covers, how much your pharmacy gets paid, and what you’ll owe at the counter. They process nearly all prescriptions filled in the United States, and three companies dominate the industry, making PBMs one of the most powerful and controversial forces in American healthcare.
What a PBM Actually Does
At the most basic level, a PBM manages the prescription drug portion of your health insurance plan. When you hand a prescription to your pharmacist, the pharmacy’s computer system contacts the PBM in real time to verify your coverage, determine your copay, and process the claim. That transaction happens in seconds, but behind it sits a complex set of decisions the PBM has already made about which drugs are covered, how much the pharmacy will be reimbursed, and what hoops you might need to jump through first.
PBMs handle several core functions:
- Formulary management: Building and maintaining the list of drugs your plan covers, organized into tiers that determine your out-of-pocket cost.
- Rebate negotiation: Cutting deals with drug manufacturers for discounts in exchange for favorable placement on the formulary.
- Pharmacy network assembly: Deciding which pharmacies are “in network” for your plan and setting the reimbursement rates those pharmacies receive.
- Claims processing: Handling the electronic transactions every time a prescription is filled.
- Utilization management: Applying tools like prior authorization and step therapy to control which drugs get dispensed and when.
Employers and insurers hire PBMs because managing prescription benefits is enormously complex. A single PBM might handle formulary decisions, rebate negotiations, and claims processing for dozens of health plans covering millions of people.
How PBMs Make Money
PBMs sit in the middle of every prescription drug transaction, and they’ve developed several revenue streams from that position. The most significant is rebates. When a drug manufacturer wants its medication placed on a PBM’s formulary, especially on a preferred tier with lower copays that drive higher sales volume, the manufacturer pays the PBM a rebate. These rebates are tied directly to formulary placement: the better the tier, the larger the rebate the manufacturer pays.
PBMs pass most of these rebates along to the insurers and employers that hire them. One estimate puts the pass-through rate at about 91 percent for commercial plans. But consumer advocates argue that the remaining share, combined with the sheer volume of prescriptions, still represents enormous retained revenue. And because the rebate system rewards higher list prices (a bigger rebate on a more expensive drug can look better than a smaller rebate on a cheaper one), critics say PBMs sometimes have a financial incentive to favor expensive brand-name drugs over lower-cost alternatives.
PBMs also generate revenue through what’s known as spread pricing. This is the difference between what the PBM charges the health plan for a prescription and what it actually pays the pharmacy. If a PBM charges an insurer $100 for a drug but reimburses the pharmacy only $70, the PBM keeps the $30 spread. The exact size of these spreads is often opaque, since PBM contracts with pharmacies and insurers contain different pricing terms.
How PBMs Affect What You Pay
If you’ve ever been told at the pharmacy counter that your medication isn’t covered, or that you need to try a different drug first, a PBM made that decision. Two of the most common tools PBMs use are prior authorization and step therapy.
Prior authorization requires your doctor to get approval from the PBM before the plan will cover a specific medication. This can mean paperwork, phone calls, and delays of days or weeks. Step therapy takes it further: it requires you to try one or more cheaper drugs first and show they didn’t work before the PBM will approve the medication your doctor originally prescribed. The stated goal is promoting cost-effective treatment, but in practice, step therapy can force patients to spend months on medications that don’t adequately treat their condition. Patients can request exceptions to step therapy requirements, and prior authorization cannot be required for emergency services.
The formulary itself shapes your costs in less visible ways. When a PBM negotiates a large rebate from one manufacturer and places that drug on a preferred tier, competing drugs (sometimes including cheaper generics or biosimilars) may end up on a higher tier with a larger copay, or excluded from the formulary entirely. Federal investigators have found evidence that PBMs and brand-name drug manufacturers sometimes enter agreements to exclude lower-cost competitors from formularies in exchange for increased rebates.
Three Companies Control the Market
The PBM industry is remarkably concentrated. The top three PBMs process nearly 80 percent of the roughly 6.6 billion prescriptions dispensed by U.S. pharmacies each year. The top six handle more than 90 percent. Those three dominant players are CVS Caremark (owned by CVS Health), OptumRx (owned by UnitedHealth Group), and Express Scripts (owned by Cigna).
What makes this concentration especially significant is vertical integration. Each of these PBMs is owned by a company that also operates a major health insurer and a pharmacy chain or mail-order pharmacy. CVS Health owns both the PBM and CVS pharmacies. UnitedHealth Group owns OptumRx alongside UnitedHealthcare insurance. This means the same parent company can insure you, decide which drugs your plan covers, process the claim, and fill the prescription at its own pharmacy.
Pharmacies affiliated with the three largest PBMs now account for nearly 70 percent of all specialty drug revenue. Specialty drugs treat complex conditions like cancer, rheumatoid arthritis, and multiple sclerosis, and they represent the fastest-growing segment of drug spending.
The Impact on Independent Pharmacies
Independent and community pharmacies have been among the most vocal critics of PBMs, and the financial pressures are real. PBMs set the reimbursement rates pharmacies receive for filling prescriptions, and those rates can fall below what the pharmacy paid to acquire the drug, a practice known as negative reimbursement. Pharmacies in PBM networks have also faced what are called DIR fees (direct and indirect remuneration), which are price concessions assessed after prescriptions are filled, sometimes weeks or months later. A pharmacy might fill a prescription thinking it will break even, only to discover months later that a retroactive fee wiped out the margin entirely.
Between 2010 and 2020, retroactive DIR fees in Medicare Part D increased by 107,400 percent. Federal regulators acknowledged that these fees could cause “already struggling pharmacies to decrease services or medication availability, and/or be unable to remain in business.” A 2024 rule change eliminated retroactive DIR fees in Medicare, but pharmacists reported that the transition created its own cash flow challenges, and other PBM practices like negative reimbursement and patient steering remain in place.
Patient steering occurs when a vertically integrated PBM directs patients toward its own affiliated pharmacies and away from independent ones. The Federal Trade Commission found that pharmacies affiliated with the three largest PBMs retained nearly $1.6 billion in excess revenue on just two cancer drugs in under three years, revenue that resulted in part from this self-preferencing.
Federal Scrutiny and Reform Efforts
The FTC launched a formal inquiry into PBM practices in 2022, and its interim findings have been pointed. The agency identified several areas of concern: self-preferencing toward affiliated pharmacies, unfair contract terms imposed on independent pharmacies, and arrangements with drug manufacturers that limit access to lower-cost generics and biosimilars. The FTC noted that reimbursement rates in PBM contracts with independent pharmacies “often do not clearly reflect the ultimate total payment amounts,” making it difficult or impossible for pharmacists to know in advance how much they’ll actually be paid.
Congress has taken up PBM reform in multiple sessions, with bipartisan proposals targeting transparency requirements, limits on spread pricing, and restrictions on self-preferencing. Key provisions under discussion would require PBMs to disclose rebate amounts to plan sponsors, pass through a larger share of rebates to patients at the pharmacy counter, and separate their pharmacy ownership from their formulary decisions. Several states have already enacted their own PBM regulations, though the patchwork of state laws creates uneven protections depending on where you live and what type of insurance you have.
The core tension is straightforward: PBMs were created to reduce drug costs through bulk negotiation and efficient claims processing, and they do perform those functions. But their position as middlemen with limited transparency, combined with the consolidation that puts insurance, pharmacy, and benefit management under one corporate roof, has created conflicts of interest that regulators, pharmacists, physicians, and patient advocates increasingly view as unsustainable.