When can I enroll in Medicare?

When can you get Medicare? You can sign up for Medicare during the initial enrollment period, which begins 3 months before the month you turn 65, continues through the month you turn 65 and for an additional three months thereafter. In other words, the initial open enrollment period is 7 months. If you do not enroll in Medicare during the initial enrollment period, then you must wait for a special enrollment period, or for the annual open enrollment period. Special enrollment period includes time while you’re covered by an employer provided health insurance policy, or during the 8 month period after employment ends or after employer provided health coverage ends. The annual open enrollment period is from January 1, through March 31, with coverage beginning on July 1.

https://www.medicare.gov/sign-up-change-plans/get-parts-a-and-b/when-sign-up-parts-a-and-b/when-sign-up-parts-a-and-b.html

The best time to purchase a Medicare supplement is during the 6 months period beginning when you are 65 AND enrolled in Medicare Part B. During that period, there is no medical underwriting, so you cannot be turned down even if you have health problems. If you wait, you might not be able to get coverage, or it might be more expensive.

https://www.medicare.gov/supplement-other-insurance/when-can-i-buy-medigap/when-can-i-buy-medigap.html