Part C and Part D are two different add-ons to Original Medicare

Part C (also called Medicare Advantage) is an alternative way to get your Part A and Part B coverage through a private insurance company instead of the government. Part D is prescription drug coverage you add to Original Medicare or Part C. They are separate programs with different purposes, different costs, and different enrollment windows.

You do not have to take either one. If you stay on Original Medicare (Part A and Part B), you can skip Part C entirely. If you take Original Medicare, you can add Part D separately. If you take Part C, it usually includes some drug coverage, though you may still want to check whether Part D would cost less or cover your specific medications better.

The choice between them affects what you pay each month, which doctors you can see, and which pharmacies you can use. Understanding what each one does will help you decide whether to enroll.

Key Takeaways

  • Part C replaces your Part A and Part B with coverage from a private insurance company, usually at a lower monthly premium but with network restrictions.
  • Part D is prescription drug coverage that you add separately to Original Medicare, or that may be included in your Part C plan.
  • Part C plans often include dental, vision, and hearing benefits that Original Medicare does not cover.
  • You can switch between Original Medicare and Part C during the annual enrollment period (October 15 to December 7), but switching back from Part C to Original Medicare can trigger a late enrollment penalty for Part D.
  • Part D premiums and coverage vary widely by plan and by pharmacy, so comparing plans before enrollment can save you hundreds of dollars per year.

How Part C (Medicare Advantage) Works

Part C is a private insurance plan that covers everything Part A and Part B cover, but through a company like UnitedHealthcare, Humana, or Anthem instead of through Medicare directly. When you enroll in Part C, you give up your Original Medicare coverage and use the Part C plan's network of doctors and hospitals instead.

Most Part C plans charge a monthly premium (in addition to your Part B premium, which you still pay to Medicare). Many charge zero premium, meaning you pay only your Part B premium and any out-of-pocket costs when you use care. Part C plans also include an out-of-pocket maximum — once you spend that amount in a year, the plan covers the rest of your care at no cost to you. Original Medicare has no out-of-pocket maximum.

Part C plans come in different types. A Health Maintenance Organization (HMO) requires you to use doctors and hospitals in the plan's network and usually requires a referral to see a specialist. A Preferred Provider Organization (PPO) lets you see out-of-network doctors, but you pay more. Some plans are Private Fee-for-Service plans, which work differently again. You choose which type when you enroll.

Part C plans often include benefits Original Medicare does not: dental cleanings and exams, vision exams and glasses, hearing exams and hearing aids, fitness programs, and transportation to medical appointments. These extras vary by plan and by region.

How Part D (Prescription Drug Coverage) Works

Part D covers the cost of prescription medications. If you stay on Original Medicare, you must enroll in a Part D plan through a private insurance company — Medicare itself does not offer Part D. If you enroll in Part C, your plan usually includes some drug coverage, though the drugs covered and the costs may differ from a standalone Part D plan.

Part D plans have a monthly premium, a yearly deductible (the amount you pay before the plan starts paying), copays or coinsurance for each prescription, and a coverage gap (sometimes called the "donut hole"). The coverage gap is a range of drug costs where you pay a higher percentage of the cost. Once your total out-of-pocket spending reaches a certain amount in a year, catastrophic coverage kicks in and you pay a small copay for the rest of the year.

Part D plans vary significantly in which drugs they cover, how much they cost, and which pharmacies you can use. A drug covered by one plan may not be covered by another, or may have a higher copay. Comparing plans before you enroll is important because the cheapest plan for one person may be expensive for another, depending on which medications they take.

If you do not enroll in Part D when you first become may be able to access, and you later enroll, you may owe a late enrollment penalty for as long as you have Part D coverage. The penalty is calculated based on how many months you went without coverage.

When You Can Enroll in Part C or Part D

The main enrollment window is the Annual Enrollment Period (AEP), which runs from October 15 to December 7 each year. During this time, you can enroll in Part C, switch from one Part C plan to another, switch from Part C back to Original Medicare, or enroll in or switch Part D plans.

If you are new to Medicare (turning 65 or becoming may be able to access due to disability or end-stage renal disease), you have an Initial Enrollment Period of seven months centered on your may be able to access month. During this time, you can enroll without a late enrollment penalty. If you miss this window, you may owe a penalty.

Special enrollment periods are available if you experience certain life events, such as moving out of your plan's service area, losing other health coverage, or having a change in income. These periods are usually 60 days long and allow you to enroll or switch plans outside the normal AEP window.

Costs: Part C vs. Original Medicare Plus Part D

Part C premiums vary by plan and region. Some plans charge zero premium; others charge $50 to $200 or more per month. You always pay your Part B premium to Medicare, regardless of whether you choose Part C or Original Medicare. Part C plans also have copays, coinsurance, and out-of-pocket maximums.

Original Medicare has no monthly premium for Part A (if you or your spouse paid Medicare taxes for at least 10 years), but Part B has a monthly premium that increases if you delay enrollment. Original Medicare also has no out-of-pocket maximum, meaning you could spend unlimited amounts on deductibles and coinsurance. However, you can buy a Medigap (supplemental insurance) plan to cover some of these costs, which adds another monthly premium.

Part D premiums range from roughly $5 to $100 per month, depending on the plan and the drugs you take. The total cost of Original Medicare plus Part D plus Medigap can be higher or lower than Part C, depending on your health, your medications, and which plans you choose.

The only way to know which option costs less for you is to compare the plans available in your area, using your current medications and doctors as a guide. Medicare.gov has tools to help you compare.

Network Restrictions and Doctor Choice

Original Medicare lets you see any doctor or hospital that accepts Medicare, anywhere in the country. Part C plans restrict you to a network of doctors and hospitals, except in emergencies. If you see an out-of-network doctor in an HMO plan, you pay the full cost yourself (except in emergencies). PPO plans let you see out-of-network doctors but charge you more.

If you have a doctor you want to keep seeing, check whether that doctor is in the Part C plan's network before you enroll. If your doctor leaves the network after you enroll, most plans allow you to switch to a different plan during a special enrollment period.

Part D does not restrict which doctors you see, but it does restrict which pharmacies you can use and which drugs are covered. Check whether your pharmacy is in the plan's network and whether your medications are on the plan's formulary (the list of covered drugs) before you enroll.

Switching Between Part C and Original Medicare

You can switch from Original Medicare to Part C, or from Part C back to Original Medicare, during the Annual Enrollment Period. If you switch from Part C to Original Medicare, you should enroll in Part D at the same time, or you may owe a late enrollment penalty later.

If you are still working and have health coverage through your employer, you may be able to delay Part B and Part D enrollment without a penalty. Once you stop working or lose that coverage, you have a special enrollment period to enroll without a penalty, but only if you enroll within 63 days of losing the coverage.

Switching plans can be complicated, and mistakes can cost you. If you are unsure whether to switch, contact your State Health Insurance information Program (SHIP), which offers free counseling about Medicare choices.

Frequently Asked Questions

Can I have Part C and Medigap at the same time?

No. If you enroll in Part C, you cannot buy a Medigap plan. Part C includes its own out-of-pocket protections, and Medigap is designed to supplement Original Medicare. If you want Medigap, you must be on Original Medicare.

What happens to my Part D coverage if I switch from Original Medicare to Part C?

It ends. Part C plans include drug coverage, but it may be different from your Part D plan. You do not need to enroll in a separate Part D plan if you have Part C, but you should review the drug coverage in your Part C plan to make sure your medications are covered.

Do I have to take Part C or Part D?

No. You can stay on Original Medicare without Part C. However, if you stay on Original Medicare, you should enroll in Part D to avoid a late enrollment penalty. If you do not take any drug coverage and later enroll, you will owe a penalty for each month you were without coverage.

How do I know which Part D plan covers my medications?

Use the Medicare Plan Finder tool on Medicare.gov. Enter your medications, and the tool will show you which plans cover them, what the copays are, and which pharmacies are in the plan's network. You can also call the plans directly or ask your pharmacist.

Can I switch Part D plans if my medication costs too much?

Yes, during the Annual Enrollment Period. You can also request a coverage exception from your current plan if a drug is not covered or if you believe there is a medical reason to use a different drug. Some plans also allow you to switch if your plan's formulary changes during the year.