What it means
With coinsurance, your share moves with the price. If a covered drug costs your plan $1,000 a month and your coinsurance is 25%, you pay about $250 that month. If the negotiated price changes, your share changes too.
That is different from a copay, which is a fixed dollar amount. Many prescription plans use copays for lower tiers and coinsurance for specialty or high-cost tiers, which is where brand-name GLP-1 medicines often sit.
Coinsurance usually starts after you meet your deductible. It stops once you reach your plan's out-of-pocket maximum for the year, after which the plan pays 100% of covered in-network costs.
Your plan's summary of benefits lists the coinsurance for each drug tier. A manufacturer savings card may lower what you pay, but these programs generally cannot be used with Medicare or Medicaid.
Why it matters
Coinsurance on a high-priced GLP-1 can cost far more than a flat copay, so it is a key number in any cost estimate.