The open enrollment period for Medicare will close at 12:01 a.m. Thursday for most seniors hoping to join for 2012 or adjust their plan within the government's main medical insurance program for those age 65 or older.

If someone is already enrolled in Medicare and likes the plan, he or she doesn't need to do anything. Changes require action.

The enrollment period is longer this year, but it began and ends earlier than last year. Medicare officials hoped the earlier close would give all parties a better chance to have situations settled by Jan. 1.

"There are no 'usual' questions because the situation is unique to each person, based on their income, drug plan and other factors," Christine McBennett said Monday as she helped seniors navigate the Medicare website at the Free Library in Center City.

McBennett is a volunteer for APPRISE, the Pennsylvania state health insurance assistance program, run locally by the Philadelphia Corporation for Aging and other organizations. Medicare is the original source of funding.

Enrollment forms must be in the Medicare office or that of the insurance company by the close of business Wednesday, so standard mail is no longer an option. People can go to www.medicare.gov to use the Medicare Plan Finder. The toll-free telephone line is 1-800-MEDICAR (1-800-633-4227).

Private insurance companies have Medicare supplemental or Advantage plans. Independence Blue Cross, which serves about 81,000 Medicare beneficiaries locally, will have walk-in service available at its Center City office at 1901 Market Street until midnight Wednesday. New members can call 1-877-393-6733 until 10 p.m. Tuesday and until midnight Wednesday night. The company website www.ibxmedicare.com can be used for enrollment.

Contact staff writer David Sell at dsell@phillynews.com or 215-854-4506. Read his blog at www.philly.com/phillypharma and on Twitter @phillypharma.