Few people think about Medicare until it's time to enroll. It's the gift you get for making it to 65 that nobody is anxious to open.

So the three dozen soon-to-be-eligibles who arrived for a "Welcome to Medicare" seminar at John Muir Health's Walnut Creek campus last week weren't exactly brimming with enthusiasm. Their mood more resembled what you'd find standing in line at the DMV.

It wasn't until instructor Pam Brown of Contra Costa County's Health Insurance Counseling and Advocacy Program began unraveling the complexity of the federal health care program that 36 sets of glazed eyes snapped into focus.

"You've all probably heard about the alphabet soup of Medicare -- parts A, B, C and D," Brown said. "We're going to demystify that for you.

"Part A is the original part, and that's hospital insurance and a few related things. Part B is medical, basically doctors and outpatient services. Part C is an alternate way to get your benefits through what's known as Medicare Advantage. Part D is the newest, just added in 2006, coverage for prescription drugs."

Medicare has been around for nearly 50 years, but for most us it's a hazy concept until we're forced to learn how it works. When all the puzzle pieces are laid down -- co-pays, deductibles, premiums, exclusions and supplemental options -- you realize how hard federal officials had to work to make it so complicated.

There's a reason the seminar took 2½ hours, and

Brown told her students that their most important job is to determine "how you want to get your Medicare coverage." If you choose parts A and B, there still are uncovered costs, so you may want to add supplemental coverage (Medigap) from a private carrier (there are 11 different categories). If you take prescription drugs, you may also want part D (private carriers also offer these plans).

If you choose part C (Medicare Advantage), you will also need part B, but not part D, because Medicare Advantage includes drug coverage. But that means selecting an HMO or PPO (private carriers again), which restricts your choice of doctors to those in network.

You could almost see the haze of confusion settling over the room.

Having access to Medicare is better than not having it, but the basic program sure is rife with peculiarities.

For instance, it will pay for eyeglasses after cataract surgery but not just because you are nearsighted. It will pay for oral surgery to your mouth and gums, but it will not pay for standard dental treatment. It will pay for blood transfusions, but only after you pay for the first three pints. (Apparently, the government wants to make sure you're really serious about needing the blood.)

Part B also offers a wide array of preventive care such as flu shots, mammograms, glaucoma tests and wellness exams. "Even expensive screenings like colonoscopies are covered," Brown said, "but not any time you want one."

So don't get the idea you can enjoy a colonoscopy on Uncle Sam's dime anytime you get the urge.

Medicare is a complex program, because that's the way politicians do things. Find out for yourself in the U.S. Department of Health and Human Services' handy little pamphlet, "Medicare & You."

It sums up everything neatly in just 150 pages.

Contact Tom Barnidge at tbarnidge@bayareanewsgroup.com. Follow him at twitter.com/tombarnidge