Turning 65 in California: A Complete Guide to Medicare Enrollment

Turning 65 is one of the most significant milestones in your healthcare journey. For California residents approaching this birthday, it marks the point when you become eligible for Medicare — and the decisions you make in the months surrounding your 65th birthday can affect your coverage and costs for years to come. Whether you're retiring, still working, or somewhere in between, understanding how Medicare works before your enrollment window opens is the best thing you can do for yourself.

This guide walks you through everything California residents need to know: when to enroll, what your options are, how much it costs, and the mistakes that trip up thousands of new enrollees every year.

Understanding Your Initial Enrollment Period

Your Initial Enrollment Period (IEP) is a seven-month window centered around the month you turn 65. It begins three months before your birthday month, includes your birthday month, and extends three months after. This is your first and best opportunity to enroll in Medicare without facing penalties or coverage gaps — and this timeline applies whether you live in California or anywhere else in the country.

When your coverage starts depends on when you sign up:

• If you enroll during the three months before your birthday month, coverage typically begins the first day of your birthday month.
• If you enroll during your birthday month, coverage starts the first day of the following month.
• If you enroll in the three months after your birthday month, coverage can be delayed by one to three months.

The takeaway: enrolling early within your IEP gives you the smoothest transition. If you miss this window entirely, you may have to wait for the General Enrollment Period (January 1 through March 31 each year), and your coverage won't start until July 1 — plus you could face late enrollment penalties that increase your premiums permanently.

The Parts of Medicare You Need to Know

Medicare is made up of several parts, and understanding what each one covers is essential before you make any enrollment decisions as a California resident.

Medicare Part A (Hospital Insurance)

Part A covers inpatient hospital stays, skilled nursing facility care, hospice, and some home health services. Most people qualify for premium-free Part A if they or their spouse paid Medicare taxes for at least 10 years (40 quarters). Even if you don't plan to use it right away, there's generally no reason to delay enrolling in Part A.

Medicare Part B (Medical Insurance)

Part B covers doctor visits, outpatient care, preventive services, durable medical equipment, and more. Unlike Part A, Part B comes with a monthly premium — $185 per month for most people in 2025 — and you'll pay a penalty for late enrollment if you didn't have qualifying coverage.

The Big Decision: Original Medicare vs. Medicare Advantage

Once you have Part A and Part B, you face the most important choice in your Medicare journey: stay with Original Medicare (and potentially add a supplement and drug plan) or enroll in a Medicare Advantage plan that bundles everything together. The plans available to you depend on where you live in California, since Medicare Part C plans are offered by county.

• Original Medicare + Medigap: Original Medicare covers about 80% of approved costs. A Medicare Supplement (Medigap) plan picks up some or all of the remaining 20%. You'll also need a standalone Part D plan for prescription drug coverage. This path gives you the most provider flexibility — any doctor or hospital that accepts Medicare nationwide, including throughout California.
• Medicare Advantage (Part C): These are private plans that replace Original Medicare. Most Medicare Advantage plans include Part D drug coverage and often add extras like dental, vision, and hearing coverage. The trade-off is that you'll typically use a network of providers in your area of California and may need referrals depending on whether you choose an HMO or PPO.

There's no one-size-fits-all answer. Your health, budget, medications, and preferred doctors in California all factor into which path makes sense. Many people find it helpful to think of it this way: Original Medicare with a Medigap plan tends to offer the most predictable costs and the widest provider access, while Medicare Advantage plans often provide lower upfront premiums and extra benefits — but with more restrictions on where you can get care in California.

Medicare Part D (Prescription Drug Coverage)

If you go the Original Medicare route, you'll want to enroll in a standalone Part D prescription drug plan. Even if you don't take many medications now, enrolling on time avoids the Part D late enrollment penalty, which accrues for every month you go without creditable drug coverage. Part D plans cover a range of prescription medications, and the specific drugs covered vary by plan — so it's worth checking your medications against plan formularies available in CA. Part D plans vary not just in which medications they cover (called a formulary), but also in what pharmacies are in-network and how much you'll pay at each coverage stage, including the donut hole.

How to Enroll in Medicare

Enrolling in Medicare is straightforward, and California residents have several options:

• Online: Visit ssa.gov to apply for Medicare through Social Security. This is the fastest method for most people.
• By phone: Call Social Security at 1-800-772-1213 (TTY: 1-800-325-0778).
• In person: Visit your local Social Security office in California. You can schedule an appointment in advance.

If you're already receiving Social Security benefits, you'll be automatically enrolled in Parts A and B when you turn 65 — your Medicare card will arrive in the mail about three months before your birthday. If you're not yet collecting Social Security, you'll need to actively apply.

After enrolling in Parts A and B, choosing a Medigap plan, Medicare Advantage plan, or Part D plan is a separate step handled through private insurance carriers — not through Social Security. Common questions about Medigap and Part D FAQs can help as you explore your choices in California.

Important timing note: Even if you're automatically enrolled, you still need to make active decisions about your coverage. Your Medigap open enrollment period — the best time to buy a supplement plan with guaranteed issue rights — starts when you're both 65 and enrolled in Part B. This six-month window won't repeat, so California residents should plan ahead to make the most of it.

What If You're Still Working at 65?

If you have health coverage through your employer (or your spouse's employer) when you turn 65, you may not need to enroll in all parts of Medicare right away — but the rules depend on the size of the employer.

Employers with 20 or more employees: Your employer plan is the primary payer and Medicare is secondary. You can delay Part B (and avoid the penalty) as long as you're covered by the employer plan. Many California residents in this situation enroll in Part A only, since it's free and doesn't interfere with employer coverage.

Employers with fewer than 20 employees: Medicare becomes the primary payer. You should enroll in both Part A and Part B when you first become eligible to avoid gaps and penalties.

When your employer coverage ends — whether you retire, get laid off, or lose coverage for any reason — you qualify for a Special Enrollment Period that gives you eight months to sign up for Part B without penalty. You may also qualify for a SEP under other circumstances. Don't wait until this window closes. Understanding Medicare Supplement enrollment periods is also important if you plan to add a Medigap policy after leaving employer coverage.

One important detail many people overlook: if you delay Part B because of employer coverage, make sure your employer provides you with documentation of creditable coverage when you leave. You'll need this to prove to Medicare that your late enrollment was justified and to avoid penalties.

Common Mistakes to Avoid

Thousands of people turning 65 make avoidable errors that cost them money or limit their options. Here are the ones that come up most often for California residents and everyone else:

• Missing the Initial Enrollment Period: This is the most expensive mistake. Late enrollment penalties for Part B add 10% to your premium for every 12-month period you could have been enrolled but weren't — and those penalties are permanent.
• Assuming Medicare covers everything: Medicare has real gaps. It doesn't cover most dental, vision, or hearing services. Long-term care isn't covered. Understanding what is and isn't included helps you plan for supplemental coverage.
• Not comparing plans: Choosing the first plan you see, or the plan your neighbor picked, without comparing your options is one of the most common regrets among new enrollees. Plans available in California vary significantly in cost, coverage, and provider networks.
• Forgetting about drug coverage: Even if your current prescriptions are minimal, skipping Part D enrollment triggers a penalty that grows every month. It's almost always better to enroll in a basic plan now. Learn when you can enroll in Part D so you don't miss your window.
• Confusing Medicare with Medicaid: They sound similar but are completely different programs. Medicare Savings Programs can help if you qualify, but Medicare itself is not income-based.
• Not understanding common Medicare myths: Misinformation about Medicare is widespread. Taking time to separate fact from fiction before you enroll can save you from costly assumptions.

Learn more about mistakes first-time enrollees make and how to sidestep them.

Costs to Expect

Medicare isn't free, even though Part A is premium-free for most people. Here's a realistic look at what you'll pay as a California resident:

• Part A: $0 premium for most enrollees. Hospital deductible of $1,676 per benefit period in 2025.
• Part B: Standard premium of $185/month in 2025. Annual deductible of $257. After that, you generally pay 20% of approved services.
• Part D: Premiums vary by plan and location within California, averaging around $35-$55/month. Costs depend on your medications and the plan's formulary.
• Medigap: If you choose Original Medicare with a supplement, Medigap premiums vary widely by plan type, location within CA, and age. Plan G, one of the most popular options, covers nearly all out-of-pocket costs after the Part B deductible. Understanding Medigap eligibility and what Medigap plans cover is an important step.
• Medicare Advantage: Many plans in California have $0 premiums (you still pay the Part B premium), but you'll typically have copays and coinsurance for services. Extra benefits like dental and fitness programs are often included.

Watch out for IRMAA: If your modified adjusted gross income exceeds certain thresholds, you'll pay an Income-Related Monthly Adjustment Amount — a surcharge on top of your Part B and Part D premiums. This catches many retirees off guard, especially if they had a high-income year recently. Certain Medicare choices can also affect your taxes, so it's worth understanding the full financial picture.

Keep in mind that Medicare costs can change annually. Premiums, deductibles, and plan benefits are updated each year, so what you pay in your first year may shift over time. Reviewing your coverage during the annual Open Enrollment Period (October 15 through December 7) ensures you're still on the best plan for your needs and budget.

For a more detailed breakdown, use our guide to finding the best overall value in Medicare plans to see how different options stack up for your situation in California.

How a Licensed Agent Can Help

Medicare is complex, and the decisions you make at 65 set the foundation for your healthcare coverage going forward. A licensed local insurance agent in California can help you:

• Compare Original Medicare + Medigap vs. Medicare Advantage side by side
• Review your prescriptions against Part D plan formularies available in CA
• Identify whether your current doctors are in-network for specific plans
• Navigate the enrollment process and deadlines
• Answer questions specific to your health situation and budget

There is no cost to you for using a licensed Medicare agent — they are compensated by the insurance carriers, not by you. Unlike searching online or calling a 1-800 number, a local agent in California knows the plans available in your area and can give you personalized advice based on your specific situation. If you're a California resident approaching 65 and feeling overwhelmed by the choices ahead of you, connecting with a local agent is one of the smartest moves you can make.