Costs
Coinsurance
Quick answer
Coinsurance is your share of a covered service as a percentage, not a fixed dollar amount. Original Medicare's Part B coinsurance is 20% after the deductible.
Plain-English definition
Coinsurance is common for high-cost services like chemotherapy, dialysis, or specialty drugs, where a fixed copay wouldn't reflect the true cost.
Why it matters
Coinsurance can be unpredictable — 20% of a $50,000 procedure is $10,000, which is why many people add supplemental coverage.
A simple example
Your Tier 5 specialty drug has 33% coinsurance. On a $1,000 drug you pay $330.
Common mistakes & misconceptions
Related terms
Copay
A copay (copayment) is a fixed dollar amount you pay for a covered service, like $10 for a primary-care visit or $47 for a Tier 3 drug.
Deductible
A deductible is the amount you pay out of pocket for covered services before your plan starts to pay. Part A, Part B, Part D, and many Medicare Advantage plans each have their own deductibles.
MOOP (Maximum Out-of-Pocket)
MOOP stands for Maximum Out-of-Pocket. It's the yearly cap on what you pay for covered in-network medical services in a Medicare Advantage plan. Once you hit it, the plan pays 100% of covered Part A and Part B care for the rest of the calendar year.
Medigap
Medigap — also called Medicare Supplement insurance — is a private policy that pays some of the out-of-pocket costs Original Medicare leaves behind, like the Part B 20% coinsurance and Part A hospital deductible.
Frequently asked questions
Coinsurance vs copay?+
Copay is a flat amount; coinsurance is a percentage.
Sources & references
📚 Where this information comes from
- Medicare.gov — official U.S. government site for people with Medicare ↗Primary source for benefits, enrollment periods, and plan comparison.
- CMS.gov — Centers for Medicare & Medicaid Services ↗Federal rulemaking, program updates, and official guidance.
- Social Security Administration — Medicare enrollment & premiums ↗Enrollment, premium withholding, and IRMAA determinations.
When you're ready, compare plans on your own terms
See Medicare Advantage plans from the insurance companies we represent, or walk the course with a licensed agent whenever you'd like a second set of eyes.
We help compare Medicare Advantage plans from the insurance companies we represent, and we don't offer every plan available in your area.
Medicare Caddies is an independent insurance agency. We are not affiliated with, endorsed by, or connected to the U.S. government, the federal Medicare program, or the Centers for Medicare & Medicaid Services (CMS). We help compare Medicare Advantage plans from the insurance companies we represent, and we don't offer every plan available in your area.