As you look through Medicare plan details, you will regularly encounter the terms "copay" and "coinsurance." Both refer to your share of a medical bill after your plan starts paying, but they function in very different ways. Grasping the difference helps you compare plans more effectively and forecast your out-of-pocket spending.
What Is a Copay?
A copay (short for copayment) is a set dollar amount you pay for a covered health care service. The amount stays the same regardless of the service's total cost. Your plan assigns specific copay amounts to different categories of care.
For instance, a Medicare Advantage plan might establish these copays:
- $20 for a primary care visit
- $40 for a specialist visit
- $10 for a Tier 1 generic prescription
- $250 for an emergency room visit
In every case, you pay the listed amount no matter what the provider's total charge is. If your specialist bills $300 and your copay is $40, you pay $40 while your plan covers the other $260. If the specialist charges $150, you still pay $40.
Copays are straightforward and easy to plan around, which is a major reason many beneficiaries favor plans that rely on them.
What Is Coinsurance?
Coinsurance is a percentage of the total cost of a covered service that you are responsible for. Rather than a flat fee, your share increases or decreases based on the price of the service.
Original Medicare applies coinsurance to most Part B services. After you satisfy your annual Part B deductible ($257 in 2026), you typically owe 20% coinsurance while Medicare covers the other 80%.
Here is what that looks like in real terms:
- A doctor visit costing $200: you pay $40 (20%), Medicare pays $160
- An outpatient procedure costing $5,000: you pay $1,000 (20%), Medicare pays $4,000
- Durable medical equipment costing $800: you pay $160 (20%), Medicare pays $640
Because coinsurance is percentage-based, your costs are directly linked to the price of the service. This can make it more difficult to anticipate expenses, particularly for costly procedures.
Where Deductibles Come In
Before copays or coinsurance take effect, you may first need to satisfy a deductible. A deductible is the amount you pay out of pocket at the beginning of a coverage period before your plan starts sharing costs.
Under Original Medicare:
- The Part A deductible (for inpatient hospital stays) is $1,736 per benefit period in 2026.
- The Part B deductible is $257 per year in 2026.
After meeting the relevant deductible, your copays or coinsurance apply to subsequent services. Some Medicare Advantage plans waive deductibles for certain services such as primary care visits, so the copay applies from your very first visit.
Copay vs. Coinsurance: Direct Comparison
Seeing the practical differences side by side can guide your plan selection:
| Feature | Copay | Coinsurance | |---|---|---| | How it's calculated | Fixed dollar amount | Percentage of total cost | | Predictability | High — you know the cost upfront | Lower — varies with the bill | | Risk for costly services | Limited — amount remains constant | Higher — a percentage of a large bill can be substantial | | Common in | Medicare Advantage plans | Original Medicare (Part B), some Advantage plans |
Some Medicare Advantage plans use a mix of both. You might pay a copay for routine office visits but coinsurance for inpatient hospital stays or surgical procedures.
Which Medicare Plans Use Which Approach?
Original Medicare depends primarily on coinsurance. Part B applies 20% coinsurance for most outpatient services after the deductible. Part A uses a deductible-based structure for hospital stays along with set daily copay amounts for extended stays.
Medicare Advantage plans more often use copays for routine services like doctor visits and prescriptions. However, many also apply coinsurance for higher-cost services such as hospital stays, outpatient surgery, or skilled nursing facility care. Each plan's Summary of Benefits specifies which cost-sharing method applies to each service. To understand the different plan structures available, see our guide to Medicare Advantage plan types.
Medigap (Medicare Supplement) plans help pay the coinsurance that Original Medicare leaves behind. For instance, Medigap Plan G covers the 20% Part B coinsurance, so you pay little or nothing beyond your premiums and the Part B deductible.
Strategies for Estimating Your Costs
Projecting your health care spending accurately requires understanding how copays and coinsurance apply to the services you use most frequently. Here are some practical steps:
- Read the Summary of Benefits. Every Medicare Advantage plan publishes a document listing copays and coinsurance for each covered service. Review it thoroughly before enrolling.
- Think about your health care usage. If you visit specialists often, compare specialist copays across plans. If you expect surgery or inpatient care, examine the coinsurance rates for those services.
- Run worst-case calculations. With coinsurance, a 20% share of a $50,000 surgery comes to $10,000. Check whether the plan includes an out-of-pocket maximum that would limit your exposure.
- Include prescriptions. Part D plans may charge copays for lower-tier drugs and coinsurance for specialty medications. A $50 copay is very different from 33% coinsurance on a $1,000 specialty drug.
- Consider Medigap. If you are on Original Medicare, a Medigap policy can eliminate or reduce your coinsurance obligations, giving you more predictable costs in exchange for a monthly premium.
Understanding how copays and coinsurance work gives you a stronger foundation for selecting the Medicare coverage that best aligns with your health needs and budget. For a broader look at what Medicare costs you in 2026, including premiums and deductibles, see our Medicare costs overview.