A guide to enrolling in Medicare at age 65, covering enrollment periods, parts A through D, Medigap policies, cost estimates, and common mistakes to avoid.
Mark your Initial Enrollment Period (7-month window around turning 65)
Your IEP starts 3 months before your 65th birthday month, includes the birthday month, and ends 3 months after. Enrolling during the first 3 months ensures coverage starts on your birthday. Delaying can result in a 1-2 month gap.
Determine if you qualify for a Special Enrollment Period
If you or your spouse have employer coverage with 20+ employees, you can delay Part B without penalty. You have 8 months after the employer coverage ends to enroll. Get written proof of coverage dates from your employer's HR department.
Know the General Enrollment Period dates if you missed your IEP
General enrollment runs January 1 through March 31 each year, with coverage starting July 1. Late enrollment incurs a 10% Part B premium penalty for each 12-month period you could have had Part B but did not. This penalty is permanent.
Note the Annual Election Period for changing plans
AEP runs October 15 through December 7 each year, with changes effective January 1. This is when you can switch from Original Medicare to Medicare Advantage or change Part D drug plans. About 30% of beneficiaries would save money by switching plans annually.
Understand Medicare Parts A Through D
Review Part A (Hospital Insurance) coverage and costs
Part A is premium-free if you or your spouse paid Medicare taxes for 40+ quarters (10 years). It covers inpatient hospital stays with a deductible of approximately $1,632 per benefit period in 2026. Most people are automatically enrolled at 65 if receiving Social Security.
Review Part B (Medical Insurance) coverage and premiums
Part B covers doctor visits, outpatient care, preventive services, and medical equipment. The standard 2026 premium is approximately $185-$190 per month, deducted from Social Security. Higher earners pay more through IRMAA surcharges starting at incomes above $103,000.
Decide between Original Medicare and Part C (Medicare Advantage)
Medicare Advantage bundles A, B, and usually D into one plan, often with lower out-of-pocket costs and extra benefits like dental and vision. About 51% of beneficiaries now choose Advantage plans. The tradeoff is restricted provider networks and prior authorization requirements.
Evaluate Part D (Prescription Drug) plans for your medications
Enter your medications into the Medicare Plan Finder tool at medicare.gov to compare total costs across plans. Part D plans have 4-5 tiers with different costs. The Inflation Reduction Act caps out-of-pocket drug costs at $2,000 per year starting in 2025.
Consider a Medigap (Medicare Supplement) policy
Medigap covers gaps in Original Medicare like deductibles and coinsurance. You have a 6-month open enrollment window starting when Part B begins, during which insurers cannot deny you or charge more for pre-existing conditions. Plans are standardized (A through N) across insurers.
Gather Required Documents
Locate your Social Security number and date of birth verification
You can enroll online at ssa.gov, by phone at 1-800-772-1213, or at a local Social Security office. Online enrollment takes about 10 minutes. Phone wait times average 30-40 minutes; calling Tuesday through Thursday before 10am yields shorter waits.
Collect proof of current employer coverage if delaying Part B
Request a letter from your employer on company letterhead stating your name, coverage dates, and that the group plan has 20 or more employees. Keep this letter permanently. You will need CMS Form L564 signed by your employer when you eventually enroll.
Review your Social Security earnings record for Part A eligibility
Create an account at ssa.gov/myaccount to verify you have 40 quarters of Medicare-taxed employment. If you have 30-39 quarters, Part A costs about $278/month in 2026. Under 30 quarters costs approximately $505/month.
Compare Plans and Costs
Use the Medicare Plan Finder tool at medicare.gov
Enter your zip code and medications to see all available plans ranked by estimated annual cost. Compare at least 5 plans. The tool accounts for premiums, deductibles, copays, and drug costs to show a true total cost estimate.
Verify your doctors and hospitals are in each plan's network
With Original Medicare, any doctor who accepts Medicare assignment is in your network (about 97% of physicians). Medicare Advantage networks are more limited. Call your doctor's billing office directly to confirm in-network status rather than relying solely on the plan directory.
Calculate your estimated total annual costs for each option
Add up: monthly premiums x 12 + annual deductibles + estimated copays based on your usage + drug costs. The average Medicare beneficiary spends $6,000-$7,000 annually on premiums and out-of-pocket costs combined.
Check plan star ratings for quality scores
Medicare rates plans from 1 to 5 stars based on quality and member satisfaction. Plans with 4+ stars often offer extra benefits. Five-star plans allow enrollment outside normal enrollment periods. About 70% of Advantage enrollees are in 4+ star plans.
Complete Enrollment and Confirm Coverage
Enroll in Part A and Part B through Social Security
The simplest method is online at ssa.gov. You will receive your red, white, and blue Medicare card in the mail within 4-6 weeks. This card shows your Medicare number (no longer your SSN) and your Part A and Part B effective dates.
Enroll in a Part D or Medicare Advantage plan directly
You can enroll through medicare.gov, by calling the plan directly, or through a licensed insurance agent at no extra cost. Agents are paid by the insurer, not by you. Confirm your enrollment by checking for a welcome packet within 2-3 weeks.
Cancel or coordinate your existing health insurance
If leaving an employer plan, coordinate your Medicare start date to avoid coverage gaps. Do not cancel employer coverage until your Medicare card arrives. If you have retiree benefits, check whether they work alongside Medicare as secondary insurance.
Notify your doctors that you now have Medicare
Give your new Medicare number to all providers and pharmacies. Ask your doctor's office to verify your Medicare eligibility before your next appointment. Billing errors in the first 60 days are common as systems update.
Frequently Asked Questions
When can I first enroll in Medicare?
Your Initial Enrollment Period (IEP) is a 7-month window that starts 3 months before the month you turn 65, includes your birthday month, and ends 3 months after. If you miss this window and do not have qualifying employer coverage, you will face a late enrollment penalty of 10% added to your Part B premium for every 12 months you were eligible but did not enroll.
What is the difference between Original Medicare and Medicare Advantage?
Original Medicare (Parts A and B) is run by the federal government and lets you see any doctor who accepts Medicare nationwide. Medicare Advantage (Part C) is offered by private insurers, usually includes drug coverage and extras like dental and vision, but restricts you to a network. About 51% of Medicare beneficiaries chose Advantage plans in 2024.
How much does Medicare cost per month?
Part A (hospital) is premium-free if you or your spouse paid Medicare taxes for 10+ years. Part B (medical) costs $185 per month in 2025, with higher premiums for incomes above $103,000 (single). Part D (drugs) averages $33 per month. Medicare Advantage plans range from $0-$200 monthly but may have higher out-of-pocket costs when you use services.
Do I need a Medicare supplement (Medigap) plan?
Original Medicare covers about 80% of approved costs, leaving you responsible for the remaining 20% with no out-of-pocket maximum. Medigap plans cover this gap. Plan G is the most popular, costing $100-$300 per month depending on your state and age. You get guaranteed acceptance during the 6-month window starting when your Part B begins.
What happens if I am still working at 65 with employer insurance?
If your employer has 20 or more employees, your group plan is primary and you can delay Medicare without penalty. Enroll in Part A (it is free) but you can wait on Part B until you leave the job. You then get an 8-month Special Enrollment Period after your employer coverage ends. For employers with fewer than 20 employees, Medicare becomes primary and you must enroll at 65.