A prescription drug deductible is the amount of money you must pay out of your own pocket before your health insurance pays for anything it covers.
A deductible can be combined for medical and prescription, or it can have separate medical and prescription drug deductibles. If the deductibles are separate, the prescription drug deductible is usually very low.
That said, the total amount of your deductible and whether or not it is combined varies based on your plan.
A prescription drug coinsurance is a form of cost-sharing with the insurance company. Rather than a set copay, you pay a percentage of that drug’s cost. While an inexpensive generic drug may be subject to a minimal copay, a rare brand-name drug may be subject to, for example, a 40% coinsurance.
This coinsurance is usually applicable after your deductible is met.
For more information, please see our post here on common insurance terms.