Understanding enrollment periods prevents costly penalties and coverage gaps. Your Initial Enrollment Period spans seven months—three months before your 65th birthday month, your birthday month, and three months after. Missing this window results in late enrollment penalties that increase your Part B premium permanently for as long as you have Medicare.

The Annual Enrollment Period runs from October 15 to December 7 each year, allowing you to switch between Original Medicare and Medicare Advantage or change prescription drug plans. Changes take effect January 1. Special Enrollment Periods apply when you experience qualifying life events like losing employer coverage, moving outside your plan's service area, or qualifying for Extra Help with drug costs.

Critical enrollment dates:

• Initial Enrollment Period begins three months before turning 65
• General Enrollment Period runs January 1 to March 31 annually
• Annual Enrollment Period allows plan changes October 15 to December 7
• Medicare Advantage Open Enrollment runs January 1 to March 31
• Special Enrollment Periods require qualifying events and documentation

Maintaining creditable coverage through employer plans may allow delayed enrollment without penalties, but verify this with your employer's benefits department before your 65th birthday.

Original Medicare allows you to see any doctor or hospital that accepts Medicare nationwide, providing maximum flexibility. However, it doesn't cover prescription drugs, requiring separate Part D enrollment, and has no out-of-pocket maximum. Many beneficiaries add Medigap supplemental insurance to cover deductibles, coinsurance, and copayments that Original Medicare doesn't pay.

Medicare Advantage plans combine Parts A, B, and usually D into one plan offered by private insurers. These plans often include extra benefits like dental, vision, and hearing coverage that Original Medicare doesn't provide. However, they typically use networks, requiring you to see in-network providers except for emergencies. Most charge copays for services rather than coinsurance percentages.

Key differences to consider:

• Original Medicare offers nationwide provider access without networks
• Medicare Advantage plans may limit you to network providers
• Advantage plans often include prescription drug coverage built-in
• Original Medicare requires separate Part D and possibly Medigap
• Advantage plans may offer lower monthly costs but higher out-of-pocket maximums

Your health needs, preferred doctors, travel habits, and budget all influence which option works best for your situation.

Understanding Medicare costs helps you budget for healthcare in retirement. Part A is premium-free for most beneficiaries but has a deductible of $1,632 per benefit period in 2024. Part B requires a monthly premium of $174.70 for most people in 2024, though higher earners pay income-related monthly adjustment amounts up to $594. The Part B annual deductible is $240.

Part D premiums vary by plan, averaging around $55 monthly, with costs depending on the specific drugs you take and the plan's formulary. The coverage gap, commonly called the "donut hole," affects costs once you reach a certain spending threshold, though recent changes have reduced its impact significantly. Extra Help programs assist low-income beneficiaries with Part D costs.

Cost components to understand:

• Part A deductible applies per benefit period, not annually
• Part B premium may increase based on modified adjusted gross income
• Part D coverage gap limits apply after reaching initial spending threshold
• Medicare Advantage out-of-pocket maximums protect against catastrophic costs
• Medigap premiums vary by plan type and your location

Medicare coordinates with other insurance when you have multiple coverage sources. If you maintain employer coverage, understanding which pays primary versus secondary prevents billing confusion and ensures claims process correctly for maximum benefit.