Medicare Part B Overview
Medicare Part B covers services and supplies considered medically necessary to diagnose or treat a disease or condition. Part B also covers preventive services meant to prevent or detect disease.
If you're collecting Social Security when you turn 65, you're typically enrolled automatically in Part B. If you have deferred Social Security and aren't enrolled in active group coverage, sign up for Part B online or go to your local Social Security office. If you have active group coverage, it’s also common to defer enrollment in Part B to a later date.
If you don't sign up when you're first eligible at age 65, you may be required to wait for the General Enrollment Period (GEP). The GEP is January 1 through March 31 each year. If you enroll during this time, your coverage begins July 1.
Part B Late Enrollment Penalty
In most cases, if you don't sign up for Part B when you're first eligible, you're required to pay a late enrollment penalty. You pay this penalty for as long as you have Part B. Your monthly premium for Part B may go up 10% for each full 12-month period that you could've had Part B, but didn't sign up. Usually, you don't pay a late enrollment penalty if you meet certain conditions that allow you to sign up for Part B during a Special Enrollment Period (SEP). Contact Social Security to find out if this penalty applies to you.
Covered Services
Part B covers:
Physician services
Diagnostic tests and lab services
Outpatient services
Rehabilitation services
Home health services
Routine preventive services
Durable medical equipment (DME)
Ambulance transportation
Limited prescription drugs (usually drugs for cancer treatment)
Diabetes care and supplies (Medicare Part D covers insulin and syringes)
Part B Costs
Part B Premium
The standard Medicare Part B premium amount in 2025 is $185 per month. However, some people who get Social Security benefits pay less than this amount. Some people pay an Income Related Monthly Adjustment Amount (IRMAA) that results in an extra charge in addition to their premium. Read Income Related Monthly Adjustment Amount (IRMAA) for more information.
Social Security tells you the exact amount of your Part B premium. The premium is usually deducted from your Social Security benefits check if you receive one. Otherwise, you receive a bill.
If you have a reimbursement account (sometimes known as a Health Reimbursement Arrangement), read Medicare Part B Premium Reimbursement to learn about getting reimbursed for your Medicare Part B premium.
Part B Deductible
In 2025, Part B services have an annual deductible of $257 that you must pay before Medicare begins to pay. After the deductible is met, you typically pay 20% of the Medicare-approved amount for most doctor services (including most doctor services while you're a hospital inpatient), outpatient therapy, and durable medical equipment (DME).