Medicare in California: Plans, Coverage, Costs and Enrollment

Medicare provides health coverage to millions of Americans, but understanding how the different parts, plans and enrollment periods work can be confusing.

For Californians approaching Medicare eligibility or already enrolled in Medicare, the first step is understanding the different ways you can receive your coverage and how options such as Medicare Advantage, Medicare Supplement insurance and Part D prescription drug coverage fit together.

Quick answer: Medicare is a federal health insurance program primarily for people age 65 and older, as well as certain younger people with disabilities or specific medical conditions. Original Medicare includes Part A and Part B. You can receive your Medicare benefits through Original Medicare or choose a Medicare Advantage plan offered by a Medicare-approved private insurance company. Depending on how you receive your coverage, you may also consider Part D prescription drug coverage or Medicare Supplement insurance.

How Does Medicare Work in California?

Medicare is a federal program, so the basic Medicare benefits available in California follow federal Medicare rules.

However, private Medicare plan availability can vary depending on where you live. Medicare Advantage plans, Medicare Part D prescription drug plans and Medicare Supplement insurance policies are offered by private insurance companies, and available options and costs can differ.

When you become eligible for Medicare, one of the most important decisions is how you want to receive your Medicare coverage.

What Are the Parts of Medicare?

Medicare is commonly divided into Parts A, B, C and D.

Medicare Part A

Medicare Part A is hospital insurance.

Part A helps cover services such as:

• Inpatient hospital care
• Skilled nursing facility care under qualifying circumstances
• Hospice care
• Certain home health care

Medicare Part B

Medicare Part B is medical insurance.

Part B helps cover services such as:

• Doctors and other health care providers
• Outpatient care
• Preventive services
• Durable medical equipment
• Certain home health services

For a more detailed comparison, read our guide to Medicare Part A vs. Part B.

Medicare Part C

Medicare Part C is another name for Medicare Advantage.

Medicare Advantage plans are offered by Medicare-approved private insurance companies as an alternative way to receive your Medicare benefits.

These plans provide your Part A and Part B benefits and usually include Part D prescription drug coverage. Many plans may also offer additional benefits not covered by Original Medicare.

Medicare Part D

Medicare Part D provides prescription drug coverage.

If you have Original Medicare, you can generally enroll in a separate Medicare Part D prescription drug plan. Most Medicare Advantage plans include Part D prescription drug coverage as part of the plan.

Learn more in our guide to Medicare Part D and prescription drug coverage.

What Is Original Medicare?

Original Medicare is the traditional Medicare program administered by the federal government.

It includes:

• Medicare Part A
• Medicare Part B

With Original Medicare, you can generally use any doctor or hospital in the United States that accepts Medicare.

Original Medicare does not include most prescription drug coverage, so beneficiaries who want prescription drug coverage can generally enroll in a separate Part D plan.

People with Original Medicare may also choose to purchase Medicare Supplement insurance to help with certain out-of-pocket costs.

What Is Medicare Advantage?

Medicare Advantage, also known as Medicare Part C, is an alternative way to receive your Medicare benefits.

Medicare Advantage plans are offered by private insurance companies approved by Medicare.

These plans provide Part A and Part B benefits and usually include Part D prescription drug coverage. Many plans may also provide additional benefits that Original Medicare does not cover.

Depending on the plan, you may need to use doctors, hospitals or other providers within the plan's network. Plans can also have their own copays, coinsurance, deductibles and other cost-sharing requirements.

See our detailed comparison of Original Medicare vs. Medicare Advantage.

What Is Medicare Supplement Insurance?

Medicare Supplement insurance, commonly called Medigap, is private insurance designed to work with Original Medicare.

Medigap policies can help pay certain out-of-pocket costs associated with Original Medicare, such as copayments, coinsurance and, depending on the plan, certain deductibles.

Medigap is not the same as Medicare Advantage. Medicare Advantage is another way to receive your Medicare benefits, while Medigap supplements Original Medicare.

Medigap policies generally do not include prescription drug coverage. If you have Original Medicare with Medigap and want prescription drug coverage, you can generally enroll in a separate Medicare Part D plan.

Read our comparison of Medicare Advantage vs. Medicare Supplement (Medigap).

Original Medicare or Medicare Advantage?

One of the biggest Medicare decisions is whether to receive your coverage through Original Medicare or a Medicare Advantage plan.

With Original Medicare:

• You receive Part A and Part B through the federal Medicare program
• You can generally use any provider in the United States that accepts Medicare
• You can add a separate Part D prescription drug plan
• You may be able to purchase Medicare Supplement insurance

With Medicare Advantage:

• You receive your Part A and Part B benefits through a Medicare-approved private plan
• Most plans include Part D prescription drug coverage
• Plans may use provider networks
• Plans may offer additional benefits not covered by Original Medicare
• Costs and plan rules vary

The appropriate coverage structure depends on your individual health care needs, prescriptions, preferred providers, budget and other coverage considerations.

How Much Does Medicare Cost?

Medicare costs depend on the coverage you have.

Potential Medicare costs can include:

• Part A premiums for people who do not qualify for premium-free Part A
• Part A deductibles and coinsurance
• Part B monthly premiums
• Part B deductibles and coinsurance
• Medicare Advantage plan premiums and cost sharing
• Part D premiums and prescription costs
• Medicare Supplement premiums

Medicare premiums, deductibles and other costs can change from year to year. Some Medicare costs can also be affected by income.

When comparing Medicare coverage, consider the total potential cost of coverage rather than looking only at a plan's monthly premium.

Who Is Eligible for Medicare?

Medicare is generally available to people age 65 and older who meet applicable eligibility requirements.

Certain people younger than 65 may also qualify for Medicare because of a disability or specific medical condition.

Your circumstances can also affect whether you need to actively enroll in Medicare or whether you are enrolled automatically.

If Medicare is new to you, start with our beginner's guide to Medicare Parts A, B, C and D.

When Should I Enroll in Medicare?

Your Medicare enrollment timing depends on your circumstances.

For many people becoming eligible at age 65, the Initial Enrollment Period is a seven-month period surrounding the month they turn 65.

Some people are automatically enrolled in Medicare, while others need to sign up.

Special enrollment rules may apply if you or your spouse are still working and you have qualifying employer-sponsored health coverage.

Missing the appropriate enrollment period can potentially result in delayed coverage or late enrollment penalties, depending on your circumstances.

See our complete guide to when and how to enroll in Medicare.

What if I'm Still Working at 65?

Turning 65 does not always mean you need to immediately enroll in every part of Medicare.

If you or your spouse are actively working and you have employer-sponsored health insurance, different Medicare enrollment rules may apply.

The size of the employer, type of coverage and whether the insurance is based on current employment can affect how Medicare coordinates with your existing coverage.

Before delaying Medicare enrollment, make sure your current coverage allows you to delay enrollment without creating a future penalty or coverage gap.

Read our guide to working past 65 and Medicare enrollment.

How Does Medicare Part D Work?

Medicare Part D helps cover prescription drugs.

Part D coverage is offered by private insurance companies that follow Medicare rules.

If you have Original Medicare, you can generally choose a separate Part D prescription drug plan.

If you choose Medicare Advantage, prescription drug coverage is included in most Medicare Advantage plans.

Each Part D plan has a formulary, which is the list of prescription drugs covered by the plan. Formularies, pharmacies, premiums and prescription costs can vary between plans.

It is important to review your prescriptions when comparing Medicare drug coverage rather than choosing a plan based only on its premium.

Can Medicare Plans Change Every Year?

Yes. Medicare Advantage and Part D plans can change from year to year.

Changes may involve:

• Monthly premiums
• Deductibles
• Copays and coinsurance
• Prescription drug formularies
• Provider networks
• Pharmacy networks
• Additional benefits

Reviewing your coverage each year can help you understand whether your current plan will continue to meet your needs for the following year.

What Is Medicare Open Enrollment?

Medicare's annual Open Enrollment Period runs from October 15 through December 7.

During this period, people with Medicare can generally review their coverage and make certain changes for the following year.

Changes made during the annual Open Enrollment Period generally take effect January 1.

Learn more in our guide to Medicare Open Enrollment 2027.

Frequently Asked Questions

Is Medicare different in California?

Medicare is a federal program, so the basic Medicare program follows federal rules throughout the United States. However, private Medicare Advantage, Part D and Medicare Supplement options and costs can vary by location and insurance company.

What are Medicare Parts A and B?

Part A is hospital insurance and helps cover inpatient hospital care and certain other services. Part B is medical insurance and helps cover doctors, outpatient care, preventive services and other medically necessary services.

What is Medicare Part C?

Medicare Part C is another name for Medicare Advantage. Medicare Advantage plans are offered by Medicare-approved private insurance companies as an alternative way to receive Medicare Part A and Part B benefits.

What is Medicare Part D?

Medicare Part D is prescription drug coverage offered through private insurance companies that follow Medicare rules.

Is Medigap the same as Medicare Advantage?

No. Medicare Supplement insurance, or Medigap, supplements Original Medicare. Medicare Advantage is an alternative way to receive your Medicare benefits through a Medicare-approved private plan.

Can I have Medicare Advantage and Medigap at the same time?

No. Medigap is designed to supplement Original Medicare and cannot be used to cover Medicare Advantage plan cost sharing.

Do Medicare Advantage plans include prescription drug coverage?

Most Medicare Advantage plans include Part D prescription drug coverage, although plan benefits and availability vary.

When can I enroll in Medicare?

Medicare has several enrollment periods, including the Initial Enrollment Period when many people first become eligible. Other enrollment opportunities may apply depending on your circumstances.

Learn More About Medicare

Medicare coverage decisions can involve several factors, including your doctors, prescriptions, health care needs, budget and other insurance coverage.

For official Medicare information, plan availability and current program rules, visit Medicare.gov or call 1-800-MEDICARE (1-800-633-4227).

This article is for general informational purposes only and is not a complete description of Medicare benefits, eligibility or plan options. Medicare rules, costs and private plan availability can change. For official information about Medicare, visit Medicare.gov or call 1-800-MEDICARE.