A copay the amount you pay every time you go to the doctor. You might have a $20 copay to see your regular doctor (primary care physician), and a $30 copay to see a specialist (like a dermatologist), for example. That number depends on your plan.
Insurance term: Coinsurance
What it really means: It’s like a copay, but it’s a percentage of the cost of a doctor visit, not a set price
Instead of being constant, like copays, a coinsurance is the share of the cost you owe when you see a doctor. “Coinsurance can be very dangerous because you really have NO IDEA what you will be charged,” says Julie Eisen, a public health expert at a New York City network of community health centers. “You are paying 10%, 20%, 30%, or 40% (depending on the plan you pick) of an unknown visit cost — and this means surprises on your bills.” And not the birthday cake kind of surprises. What’s more, neither copay nor coinsurance count toward your deductible. You start handing over the copays for “covered” services right away, and coinsurance only really kicks in after your deductible anyway. They do both (thankfully!) count for something, a different (higher) number known as the "out-of-pocket maximum."