Medigap vs. Medicare Advantage vs. Part D: Which Path Is Right for You?

Once you enroll in Original Medicare (Parts A and B), the coverage gaps become obvious quickly. There is no out-of-pocket maximum on Part A and Part B, a 20% coinsurance applies to most outpatient services with no ceiling, and Part B excess charges can hit you when a provider doesn't accept Medicare assignment. Medigap (Medicare Supplement Insurance) exists to plug those holes, but it is not the only way to manage Medicare costs. The two main alternatives are Medicare Advantage (Part C) plans, which bundle Parts A, B, and usually Part D into one policy, and standalone Medicare Part D prescription drug plans combined with Original Medicare.

Choosing between these paths is one of the most consequential financial decisions a 65-year-old will make. Premiums, networks, out-of-pocket limits, and enrollment windows all differ, and switching later can be difficult or impossible. Below is a practical comparison to help you match the right coverage to your health, budget, and lifestyle.

Quick Comparison: Medigap, Medicare Advantage, and Part D

  • Medigap – Supplemental insurance that pays some or all of your Part A and B cost-sharing. Works with Original Medicare and any provider that accepts Medicare nationwide. Usually paired with a standalone Part D plan.
  • Medicare Advantage – A private alternative to Original Medicare that replaces Part A and Part B with a managed-care plan (HMO, PPO, or PFFS). Often includes Part D drug benefits and extras like dental or vision.
  • Part D Only – A standalone prescription drug plan added to Original Medicare. Useful if you want Original Medicare's flexibility but need drug coverage. Leaves you exposed to medical cost-sharing without a Medigap policy.

How Medigap Plans Work

Medigap policies are standardized in most states and identified by letters (A, B, D, G, K, L, M, and N, plus high-deductible G). Each plan letter offers a fixed set of benefits, so a Plan G from one insurer must cover exactly what a Plan G from another insurer covers. The only real differences are price, customer service, and rate-increase history.

Plan G is currently the most popular option for new enrollees because it covers everything Plan F did except the Part B deductible (which is $240 in 2024). That means Plan G covers Part A coinsurance, Part B coinsurance (the 20%), Part A hospice coinsurance, skilled nursing facility coinsurance, the Part A deductible, Part B excess charges, and foreign travel emergencies. The only out-of-pocket medical cost you face is the annual Part B deductible.

Plan N is a close second. It covers the same major items as Plan G but requires small copayments for some office and emergency visits (up to $20 for office visits and up to $50 for ER visits that don't lead to admission) and does not cover Part B excess charges. Premiums for Plan N typically run $30 to $60 per month less than Plan G.

Premiums vary widely by age, zip code, gender, and insurer. A 65-year-old in Dallas might pay $110 per month for Plan G, while the same age and plan in Manhattan could exceed $300. The best way to compare is to request quotes from at least three to five highly rated insurers and check each company's historical rate increases, not just the introductory premium.

How Medicare Advantage Compares

Medicare Advantage plans often look attractive on the surface because many advertise $0 premiums. That figure is misleading, however, because you still pay your Part B premium (and possibly more if the plan has a premium), and you trade Original Medicare's open provider network for a restricted one.

The core trade-off is structure:

  • Network – Most MA plans are HMOs or PPOs. Going out of network can mean no coverage or significantly higher copays. With Original Medicare plus Medigap, you can see any provider in the country who accepts Medicare, which is over 90% of U.S. doctors.
  • Out-of-pocket maximum – MA plans cap your annual medical spending (often $4,000 to $8,500 in-network for 2024). Original Medicare has no cap, which is exactly what Medigap solves.
  • Prior authorization – Many MA plans require approval before procedures, tests, or specialist visits. Medigap has no such requirement.
  • Extras – Most MA plans include Part D, dental, vision, hearing, gym memberships, and over-the-counter allowances. Medigap does not include any of these; you must buy Part D separately and pay out of pocket for dental and vision.

Medicare Advantage makes sense for people who want lower monthly premiums, are comfortable staying in a network, don't travel frequently, and want bundled extras. It is risky for people with chronic conditions, complex medication regimens, or strong provider preferences, because frequent prior authorizations and network restrictions can complicate care.

Cost Comparison: A Realistic Scenario

Numbers tell the real story. Consider a healthy 67-year-old who sees a primary care doctor four times a year, a cardiologist twice, has two brand-name prescriptions, and needs an outpatient procedure:

  • Medigap Plan G + Part D: $160 Medigap premium + $40 Part D premium = $200/month. Out-of-pocket for care: only the $240 Part B deductible. Total annual cost: about $2,640 plus the deductible.
  • Medicare Advantage HMO with drug coverage: $0 plan premium + $174.70 Part B premium = $174.70/month. Copays might include $15 per PCP visit, $35 per specialist visit, $250 for outpatient surgery, and prescription copays. Annual cost could easily reach $3,000 to $4,500 depending on usage.

If the same person has a bad year and is hospitalized for five days, the MA plan's daily copays and out-of-pocket max kick in. With Medigap Plan G, the hospital stay costs nothing beyond the premium.

Switching and Enrollment Rules That Matter

The federal Medigap "guaranteed issue" window lasts six months from the month you turn 65 and enroll in Part B. During this window, insurers cannot deny you coverage or charge more for pre-existing conditions. After that window closes in most states, insurers can use medical underwriting, which means they can decline you or charge higher rates based on health history.

Medicare Advantage has an annual open enrollment period from October 15 to December 7, plus a Medicare Advantage Open Enrollment Period from January 1 to March 31. You can switch MA plans yearly, but switching back to Medigap later may require underwriting unless you qualify for a special enrollment situation.

If you anticipate wanting Medigap eventually, the safest move is to enroll during your initial six-month window, even if the premiums feel high. Once that window closes, getting back in can be difficult.

How to Decide

Use this framework to choose:

  • Choose Medigap if you value provider freedom, travel frequently, have chronic conditions, want no prior authorization hassles, and can afford higher monthly premiums for predictable costs.
  • Choose Medicare Advantage if you want low premiums, are healthy, like bundled dental/vision/hearing benefits, and are willing to stay in network and follow plan rules.
  • Choose Part D only with Original Medicare only if your budget cannot handle Medigap premiums and you accept the risk of uncapped 20% coinsurance on major care.

Whatever you choose, compare at least three carriers, review the formulary for your specific prescriptions, and confirm your preferred doctors and hospitals are in-network before enrolling. The right answer depends on your health, finances, and tolerance for paperwork, and the only way to find it is to compare the actual numbers on the table in front of you.