What Is Medicare Part B?

Medicare Part B is the medical insurance portion of Original Medicare. It covers doctor visits, outpatient care, preventive services, lab tests, durable medical equipment, and many other services delivered outside the hospital.

Part B has a standard monthly premium that most beneficiaries pay, with higher-income individuals paying more through an income-related adjustment (IRMAA). There is also an annual deductible and a 20% coinsurance on most services.

Together, Part A and Part B make up what's called Original Medicare. Many people add a Medicare Supplement (Medigap) plan or choose a Medicare Advantage plan to help cover the out-of-pocket costs that Part B alone leaves behind.

If you delay enrolling in Part B without other creditable coverage (like a current employer plan), you may face a lifetime late-enrollment penalty. Timing matters — review your options before your 65th birthday window closes.