Your premium will be increased if you do not apply at age 65.

Enrollment rules are very strict. Initially, you have seven months to sign up for medical insurance (Medicare Part B). This seven-month period begins three months before your 65th birthday, includes the month you turn 65 and ends three months after that birthday. If you enroll during the first three months of your enrollment period, your medical insurance protection will start with the month you are eligible. If you enroll during the last four months, your protection will start one to three months after you enroll.

If you do not enroll during this initial enrollment period, each year you are given another chance to sign up during a general enrollment period from January 1 through March 31. Your coverage begins the following July. Your monthly premium increases 10 percent for each 12-month period you were eligible but didn't enroll.

EXCEPTION: If you are covered by an employer or union group health plan through your or your spouse's current or active employment, you may qualify for a special enrollment period (SEP).

The special enrollment period is a period of time, during which you may enroll.  If you did not enroll during your initial enrollment period because you are covered under a group health plan based on your own current employment or the current employment of any family member.

The special enrollment period may occur during any month you are covered under a group health plan based on current employment, or during the 8-month period that begins the first full month after employment or group health plan coverage ends, whichever comes first.

For more information on how to qualify for a special enrollment period (SEP), see the Social Security Administration’s publication Medicare  at http://www.socialsecurity.gov/pubs/10043.html.