You can generally join any Medicare private health plan (such as an HMO, PPO or PFFS) in your county. Medicare private health plans are sometimes known as Medicare Advantage plans. Before joining any plan, make sure your doctor accepts this insurance and that any doctors you want to see accepts new patients in that plan.

It’s best to enroll in a Medicare private health plan by calling 800-MEDICARE rather than enrolling through the new plan. However, there are only certain times when you can join a Medicare private health plan. You must be enrolled in both Medicare parts A and B to sign up for a private health plan.

You can join a private health plan at the following times:

• Your Initial Enrollment Period (IEP) for Part B. The IEP is the seven-month period surrounding the month you become eligible for Medicare. It includes the three months before the month you become eligible for Medicare, the month you become eligible for Medicare, and the three months after the month you become eligible.
• During a Special Enrollment Period (SEP) for Part B if you qualify for one. You can delay enrolling in Part B without penalty if you have health insurance through your or your spouse’s current job when you become eligible for Medicare. You get a Special Enrollment Period while you are working or when you stop working or lose the employer-based coverage. The SEP gives you eight months to enroll in Part B after you lose your group health coverage or you (or your spouse) stop working, whichever comes first. If you get an SEP, you can enroll in a private health plan during the three months before your Medicare parts A and B coverage begins. Your time to sign up for a private health plan ends when you have both parts A and B.
• During the General Enrollment Period (GEP). If you sign up for Medicare during the General Enrollment Period (January through March of each year), your Medicare coverage starts July 1. You can sign up for a private health plan April through June of that year.
• During Fall Open Enrollment. Starting in 2011, the Fall Open Enrollment Period goes from October 15 to December 7. You can switch Medicare private health plans during this period or sign up for one for the first time. Coverage under your new plan begins January 1 for changes you make during Fall Open Enrollment. Note: You can’t enroll in a Medicare Medical Savings Account (MSA) plan during Fall Open Enrollment.
• You have a Special Enrollment Period (SEP) to enroll in a Medicare private plan outside the above enrollment periods. 

 Medicare Private Plan Special Enrollment Period (SEP) Chart

To learn more about enrolling in a Medicare Medical Savings Account (MSA) plan, click on the link in the GO TO box.

Note: If you have End-Stage Renal Disease (ESRD), you can usually only join a private health plan if it is a "Special Needs Plan" that specifically accepts people with ESRD, or if you’re in a Medicare private health plan that’s leaving your area.

Enroll early during an enrollment period to make sure that your new coverage starts when it should.

If you already have a Medicare private health plan and want to switch into a new one, you should usually enroll in the new plan without disenrolling from your old plan. It’s best to enroll in a new Medicare private health plan by calling 800-MEDICARE, rather than by calling the new plan. That will help you minimize potential data transfer problems between Medicare and the plans.

You will be automatically disenrolled from your previous Medicare plan when your new coverage starts.

learn how enrollment periods affect your ability to change your Medicare health plans, click on the link "Can I change my Medicare health plan at any time?" in the GO TO box.

To learn how private health plans work with retiree benefits, click on the links in the GO TO box.