Unlike other Medicare Initial Enrollment Periods, the Open Enrollment Period
for Medicare Supplements or Medigap policies begins when you first have
both Medicare Part A (have turned 65) and Medicare Part B coverage.
enrollment period continues for 6 months after you have enrolled in Medicare Part B.
During this 6-month enrollment period, you have "guaranteed issue" rights and a Medicare Supplement provider
cannot subject you to medical underwriting or deny you coverage because
of health problems or make you wait for Medicare Supplement coverage
because of your health (with the except of pre-existing conditions) or
charge you a higher premium for a Medigap policy because of your health.
(Depending on your state, some Medicare Supplements may be available for
people under 65 with both Medicare Part A and Medicare Part B).
So if you enrolled in Medicare Part A when you first turn 65, but your
Medicare Part B enrollment is delayed, for example, because you have an
employer health policy, you will have an open enrollment period for a
Medicare Supplement that will continue for 6 months after you first
enroll in Medicare Part B.