What is coinsurance?
The same percentage, a very different dollar amount.
You know it's a percentage. This guide shows why that percentage can mean $40 one visit and $1,000 the next — and why your rate itself isn't always one fixed number.
Show me how it scales ↓Quick recap
Coinsurance is a percentage of the allowed amount you may pay, generally after your deductible is met. Need the basics and a dollar example? See the full breakdown → — this page goes deeper into how that percentage actually plays out.
Why 20% doesn't mean a fixed dollar amount
Example only, using a 20% coinsurance rate — your actual rate and costs will differ.
This is why coinsurance feels unpredictable
A copay is the same every time. Coinsurance scales with the cost of the service — which is exactly why bigger procedures come with bigger uncertainty, until you reach your out-of-pocket maximum.
Your coinsurance rate can vary within the same plan
In-network vs. out-of-network
Many plans apply a higher coinsurance percentage for out-of-network care.
Drug tiers
Specialty medications often carry a different — frequently higher — coinsurance rate than standard prescriptions.
Durable medical equipment
Items like wheelchairs or CPAP machines sometimes have their own coinsurance rate, separate from office visits.
Coinsurance stacks until your out-of-pocket maximum
There's a ceiling
Every coinsurance payment generally counts toward your out-of-pocket maximum. Once you reach it, your plan generally pays 100% of covered costs for the rest of the plan year.
Where patients get tripped up
"My coinsurance is the same for every service."
Not necessarily — network status, drug tier, and service type can all change the applicable rate.
"Coinsurance is calculated from the sticker price."
It's generally calculated from the negotiated allowed amount, which is usually lower than the initial charge.
"Coinsurance and copay are the same thing."
A copay is a fixed dollar amount; coinsurance is a percentage that scales with the cost of the service.
"Coinsurance never ends."
It generally stops once you hit your out-of-pocket maximum for the plan year.
In Canada? Coinsurance mostly applies to a different layer of coverage.
Jump to the Canadian guide ↓Mostly a private-plan concept
For core medically necessary doctor and hospital care, provincial/territorial public health insurance generally doesn't use coinsurance. It's far more common on the private or workplace benefits layer — especially for prescription drugs, where coinsurance percentages can vary by drug type — and works similarly to the concepts on this page.
What are you trying to do?
See the full cost-sharing breakdown
Read the guide →Understand my deductible
Read the guide →Check if a service is covered
Read the guide →Read my EOB
Read the guide →What is a copay?
Understanding out-of-pocket maximums
Common questions about coinsurance
Does coinsurance apply before or after my deductible?
Generally after — most plans have you pay 100% up to your deductible, then coinsurance takes over for a percentage share.
Can I estimate my coinsurance before a procedure?
Often yes — ask your provider's billing office or your insurer for the allowed amount and your applicable rate before scheduling.
Does coinsurance apply to prescription drugs too?
Often yes, especially for higher drug tiers — though many plans use a flat copay for lower-tier generic medications instead.
Why did my coinsurance amount look wrong on my EOB?
Common reasons include an unmet deductible, an out-of-network provider, or a different rate applying to that specific service — check the remark codes on your EOB.
Know the percentage. Know what it means for you.
Understanding how coinsurance scales helps you anticipate costs before a bigger procedure.