The 2026 benefits-budget question at almost every mid-size and large employer is whether to cover GLP-1 drugs for weight loss — and what it will cost. The instinct is to multiply the drug's list price by the number of employees and recoil. That math is wrong in both directions: it ignores rebates, cost-share, and low persistence that pull the number down, and it ignores that uptake — how many members actually fill — is what really drives the total. This calculator models the cost the way a benefits actuary would: covered lives times uptake times a coverage-design factor, netted for rebates and cost-share, annualized for discontinuation, expressed as PMPM.

Why uptake and coverage design dominate the number

A GLP-1's list price of roughly $1,000–1,350 a month is real, but the plan almost never pays it. PBM rebates knock a quarter or more off gross, the member's cost-share covers part of the rest, and — critically — a large share of members discontinue within the first year, so the average utilizer isn't filling for all twelve months. Net that down and the cost per utilizer is far below the headline sticker.

The bigger lever is how many members fill at all. Open coverage lets uptake run free; prior authorization (a BMI threshold and documentation) and step therapy (try a cheaper option first) each cut utilization sharply. In this model, moving from open coverage to prior authorization takes the same plan from about $38 PMPM to about $23 PMPM — a one-third reduction — without changing the drug's price at all. That's why the coverage-design decision, not the price negotiation, is where employers spend most of their attention.

Reading PMPM, annual cost, and premium impact

The headline is PMPM — the added cost spread across every covered member per month — because that's the unit benefits budgets and trend are set in. The annual plan cost and cost-per-employee figures translate it into totals a CFO recognizes, and the premium-impact percentage expresses the add as a share of a typical medical premium (the model assumes roughly $700 PMPM, near the 2025 average single-coverage premium).

The Coverage Scenarios tab lines up no-coverage, step therapy, prior authorization, and open coverage on identical inputs so the utilization lever is visible at a glance. The Per-Employee Impact tab converts the same result into the per-employee and premium view that HR and finance use when they present a coverage recommendation to leadership. Together they answer the two questions employers actually ask: what does this cost, and how much does it move the premium?

What this model can't tell you

This is a planning model, not an actuarial quote. It uses your entered assumptions — uptake, net price, rebate, cost-share, discontinuation — rather than your plan's real claims history, and the coverage-design factors are representative, not contract-specific. Offsetting medical savings (fewer diabetes, cardiovascular, or obesity-related claims) are included only if you enter them, and deliberately so: those savings are slow to materialize, uncertain in magnitude, and easy to overstate.

Actual cost depends on your census and age mix, the specific drugs and doses your members use, your PBM contract and rebate terms, stop-loss structure, and how tightly utilization is managed over time. Treat the result as a directional planning figure and confirm it with your broker, PBM, or actuary before setting a coverage policy or a budget.