Most people need both Part A and Part B for hospital and medical coverage. You do not always have to enroll in both at the same time. Whether you can safely wait depends on your other insurance and how it works with Medicare.

Why Most People Enroll in Both

Part A mainly covers inpatient hospital and certain facility-based care. Part B covers doctors, outpatient care, preventive services, and durable medical equipment. Having only Part A can leave you without primary care, specialist, outpatient surgery, and many other medical benefits through Medicare. Even during an inpatient stay, doctors’ services are generally covered by Part B.

You must have both Part A and Part B to join Medicare Advantage. To join a stand-alone Part D drug plan, you generally need either Part A or Part B. You generally need both to buy Medigap.

When Might Someone Delay Part B?

You may be able to delay Part B without a penalty if you have qualifying group health coverage based on your or your spouse's current employment. Employer size and which coverage pays first matter.

Retiree coverage, COBRA, VA benefits, and Marketplace coverage do not create the same Part B enrollment protection as active-employment group coverage. Do not delay based only on having another insurance card.

Check Before Declining Coverage

Ask the benefits administrator in writing:

  • Does the employer plan pay before Medicare after age 65?
  • Must I have Part A or Part B for the plan to pay normally?
  • Is the drug coverage creditable, meaning it is expected to pay at least as much as standard Part D?
  • When will current-employment coverage end?

If you or your employer puts money into a Health Savings Account (HSA), check when those contributions must stop before enrolling in any part of Medicare.

If another plan requires Medicare to pay first, declining Part B can leave bills unpaid even when you can enroll later without a penalty. Use the payment-coordination rules and separately confirm whether your delay qualifies for an enrollment period.

Medicare policy sources last checked: October 8, 2026.