Two Very Different Ways to Share Costs
Medicare uses two main types of cost-sharing when you receive care: copays and coinsurance. Understanding the difference is not just a matter of vocabulary. It has a direct and significant impact on how much money you could owe after a medical event, and which type of supplemental coverage will protect you best.
A copay is a fixed dollar amount you pay for a specific service, regardless of what that service actually costs. For example, a Medicare Advantage plan might charge a $20 copay for a primary care visit and a $45 copay for a specialist visit. Whether the actual cost of that visit is $150 or $500, you pay $20 or $45. Copays are predictable and easy to budget.
A coinsurance is a percentage of the actual cost of a service. After Medicare pays its share, you pay the remaining percentage. Original Medicare Part B charges 20% coinsurance on most outpatient services. That sounds modest until you consider that 20% of a $50,000 procedure is $10,000, and 20% of a $200,000 hospitalization is $40,000.
How Original Medicare Uses Coinsurance
Original Medicare Part B charges 20% coinsurance on most covered outpatient services after you have met the annual Part B deductible ($257 in 2025). There is no annual cap on this coinsurance. It applies every time you receive a covered service. If you have multiple specialist visits, imaging studies, outpatient surgeries, and chemotherapy in a given year, the 20% adds up with no ceiling.
Part A (hospital) uses a different structure. After you pay the Part A deductible ($1,676 per benefit period in 2025), your first 60 days in the hospital are covered at 100%. Days 61 through 90 cost you $419 per day in coinsurance. Beyond day 90, you enter "lifetime reserve days" at $838 per day. The Part A deductible resets with each benefit period, not each calendar year, which means a long illness that spans multiple hospitalizations could trigger multiple deductibles in a single year.
Real-Dollar Examples
Consider these scenarios under Original Medicare with no supplemental coverage:
- Outpatient surgery: Total billed cost $30,000. Medicare pays $24,000 (80%). Your 20% coinsurance: $6,000.
- Chemotherapy (12 sessions at $15,000 each): Total billed $180,000. Medicare pays $144,000. Your coinsurance: $36,000.
- 80-day hospital stay: Part A deductible ($1,676) plus coinsurance on days 61-80 (20 days x $419 = $8,380). Total: approximately $10,056 plus any Part B coinsurance for physician services during the stay.
These are not extreme edge cases. They represent realistic scenarios for people with cancer, cardiac events, or serious accidents.
How Plan G and Medicare Advantage Address This
Medigap Plan G is specifically designed to eliminate nearly all of the coinsurance exposure under Original Medicare. Plan G covers the Part A deductible, the Part A coinsurance for days 61-90 and beyond, the Part B coinsurance (that 20%), the Part A and B blood deductible, skilled nursing facility coinsurance, and foreign travel emergency care. The only thing you pay under Plan G is the annual Part B deductible. After that, your coinsurance exposure is essentially zero.
Medicare Advantage plans add a different protection: the Maximum Out-of-Pocket (MOOP). Federal rules cap the in-network MOOP at $9,350 in 2025. This means that no matter how much coinsurance and copays accumulate during the year, once you hit the MOOP, the plan covers 100% of in-network covered services for the remainder of the year. This is a meaningful protection, though it is important to understand that the MOOP resets every January 1 and applies only to in-network costs on most HMO plans.
Choosing the Right Protection for Your Situation
If you want the greatest protection against coinsurance exposure, Medigap Plan G with Original Medicare offers near-comprehensive coverage nationwide. If you are comfortable with a network and an annual MOOP, Medicare Advantage provides cost certainty through the MOOP mechanism. Either way, leaving yourself exposed to unlimited 20% coinsurance under Original Medicare alone is a significant financial risk that most people cannot absorb.
Call Insurance Innovators LLC at (530) 395-5309 to review which approach makes the most sense for your health history, medications, and financial situation.