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How to Estimate Total Out-of-Pocket Costs With Medicare Supplement

What You’re Actually Paying For (And What Most People Miss)

Most people shopping for a Medicare supplement plan focus entirely on the monthly premium and stop there. That’s a mistake I’ve seen cost people hundreds of dollars a year, sometimes more.

Here’s the thing: your true out-of-pocket cost with a Medigap plan has three parts. There’s the monthly premium you pay the insurance company, the cost-sharing that still falls on you under your specific plan, and the underlying Medicare deductibles that may or may not be covered depending on which plan you chose. Add all three together and you get a real number. Ignore any one of them and your estimate is garbage.

Let me walk you through how to actually do this calculation, so you’re comparing plans on equal footing and not getting surprised by a bill six months after you’ve enrolled.

Start With Medicare’s Built-In Cost Structure

Before you can estimate your Medigap costs, you need to understand what Medicare itself charges. Original Medicare has two main deductibles that matter here.

The 2026 Part B deductible is $257. That’s the amount you pay out-of-pocket each year before Medicare starts covering your outpatient services, doctor visits, lab work, and similar care. After that deductible, Medicare pays 80% and you owe 20% with no cap, which is the entire reason Medigap exists.

The 2026 Part A deductible is $1,676 per benefit period. This one confuses people because it’s not annual — it resets each time you start a new hospital benefit period. If you get admitted to the hospital twice in a year and the stays are separated by more than 60 days, you could owe that deductible twice. For someone who stays generally healthy, this might never come up. For someone managing a chronic condition, it absolutely can.

Medicare also charges daily coinsurance for extended hospital stays. Days 61 through 90 cost you $419 per day in 2026. After 90 days, you’re burning through your 60 lifetime reserve days at $838 per day. These numbers are why a single serious hospitalization can wreck someone’s finances without a supplement plan covering them.

How Each Medigap Plan Changes Your Actual Exposure

Not all Medigap plans cover the same things, and this is where the real math happens. I’m going to focus on the plans most people actually buy, because there are technically 10 standardized plan types and most of them aren’t worth your time to analyze.

Plan Part A Deductible Part B Deductible Part B 20% Coinsurance Typical Monthly Premium (Age 65)
Plan G Covered You pay $257/year Covered $100-$200/month
Plan N Covered You pay $257/year You pay up to $20/visit copay $80-$140/month
Plan F Covered Covered Covered $130-$250/month

Plan F is only available to people who became Medicare-eligible before January 1, 2020. If you turned 65 after that date, it’s not an option for you.

Plan G is what I’d point most new Medicare enrollees toward. You pay the $257 Part B deductible once a year, and after that, virtually everything else is covered. Your maximum exposure is highly predictable. Plan N costs less per month but adds copays of up to $20 per doctor visit and up to $50 for emergency room visits that don’t result in inpatient admission. If you see doctors frequently, those copays add up fast and can erase the premium savings.

How to Build Your Actual Annual Cost Estimate

Here’s the formula I’d use. Take your monthly premium and multiply by 12. Add the deductibles your plan doesn’t cover. Then estimate your copays or remaining cost-sharing based on how often you realistically use medical care.

Let’s use a real example. Say you’re a 67-year-old in Ohio on Plan G, paying $145 per month in premiums. You see your primary care doctor four times a year, you had one specialist visit, and you stayed healthy otherwise.

Now run that same person on Plan N at $115 per month with five doctor visits.

Plan N saves $260 per year in this scenario. But if that same person sees specialists more often, or has a year with an unexpected illness that means 12 or 15 visits, the math flips. That’s not a scare tactic — it’s just the honest arithmetic. Plan N rewards light users. Plan G rewards predictability.

One thing to factor in that most people don’t: premium inflation. Medigap premiums increase every year, and they typically increase faster than Medicare’s deductibles. When you’re comparing Plan G to Plan N today, you’re also betting on which plan’s premiums will stay more manageable over the next 10 to 15 years. I’d rather lock into a slightly higher premium now on a plan with no surprises than chase savings on a plan where cost-sharing can grow unpredictably.

The Mistake That Costs People the Most Money

I’ve seen this happen over and over: someone picks a lower-premium plan thinking they’re saving money, then mentally stops tracking their actual spending. They assume they’re ahead. They’re often not.

The most common version of this mistake is choosing a high-deductible Plan G (HD-G) without understanding how the deductible works. In 2026, the HD-G deductible is $2,870. That means you pay the first $2,870 of Medicare-covered costs entirely out of pocket before the plan kicks in. The monthly premium is much lower, sometimes $30 to $60 per month, which looks spectacular on paper.

The math only works in your favor if you stay genuinely healthy year after year. And here’s what people don’t think about: you’re choosing this plan at 65 or 67, but you’re going to be on it at 75 or 80 too. The odds that you’ll stay under that $2,870 threshold get worse over time, not better. I’ve talked to people who picked HD-G at 65, had a moderately rough year at 72, and paid the full deductible plus their premiums and came out worse than they would have on standard Plan G.

That doesn’t mean HD-G is never the right call. If you’re exceptionally healthy, have significant savings you can use to cover a bad year, and are disciplined about running the numbers annually, it can work. But it’s not a plan I’d recommend casually to someone who just wants predictable costs.

When Your Health History Should Change the Math

If you’re estimating future costs, you can’t just look at what you spent last year. You need to think about where you’re headed.

Someone with well-managed Type 2 diabetes, for example, probably sees their primary doctor four times a year, an endocrinologist twice, and maybe an ophthalmologist once annually. That’s seven visits right there, plus labs. Under Plan N, seven visits at $20 each adds $140 in copays annually. Under Plan G, that’s $0 in copays. The premium gap between the two plans needs to be wider than $140 per month before Plan N wins on pure math, and in most states, it isn’t.

People managing heart disease, COPD, or any condition that involves regular specialist care should almost always lean toward Plan G. The math is just cleaner, and the protection is more complete. Healthy people with no chronic conditions have a real argument for Plan N or HD-G, but they need to run the numbers honestly and revisit them every few years.

I’d also tell anyone approaching 70 to think hard before switching to a lower-premium option. In most states, once you’re past your initial enrollment window, switching plans requires medical underwriting. If your health has changed, you might not qualify for a better plan later. The time to lock in good coverage is when you’re healthy enough to get it.

Bottom Line

For most people, Plan G gives you the most predictable total out-of-pocket cost, and predictability is worth something when you’re on a fixed income and can’t afford surprises. Run the full annual math — premiums plus all remaining cost-sharing — not just the monthly premium, and you’ll usually find that Plan G’s advantage is bigger than the sticker price suggests. If you’re in excellent health and can comfortably absorb a bad year financially, Plan N is worth a real look, but go in with eyes open and a calculator in hand.

Frequently Asked Questions

Does Medicare supplement cover prescription drugs?

No. Medigap plans don’t cover prescription drugs at all. You need a separate Part D plan for that, and your drug costs are entirely separate from the out-of-pocket estimate we’re talking about here. Factor your Part D premium and expected drug costs into your total Medicare budget as a separate line item.

Can my Medigap premium increase every year?

Yes, and it will. Medigap premiums increase annually, typically between 3% and 8% per year depending on your insurer, your state, and how your plan is priced. This is one reason I’d rather see someone start on a slightly lower-premium plan with a strong carrier than chase the lowest possible premium with a company that has a history of aggressive rate increases.

What if I only go to the doctor once or twice a year — is Medigap even worth it?

Probably yes, but the math is closer. Light medical users sometimes do fine with Medicare Advantage instead of Medigap. But Medigap’s value isn’t just about what you spent last year — it’s about protection against the year you get a serious diagnosis, need surgery, or spend time in the hospital. One hospital stay without a Medigap plan can cost you thousands. One hospital stay with Plan G costs you essentially nothing beyond your annual deductible.

Are Medigap costs the same no matter which insurance company I choose?

The coverage is standardized by law, meaning a Plan G from one company covers exactly the same things as a Plan G from another. But the premiums vary significantly between insurers for the exact same plan. Shopping multiple carriers in your state for the same plan type is one of the easiest ways to save money without giving up any coverage. In some states, the price difference for the same plan can be $50 or more per month.

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