Doctors often find it difficult to work a 45-minute wellness visit into an already overstretched schedule. Many say that they've been covering its elements for years in other ways, by working a discussion of preventive measures into a regular visit when examining a patient with, say, diabetes or heart problems. "A lot of this happens on the fly in a primary care practice," Ejnes says.

Medicare pays doctors according to numerical billing codes they submit for each service. In 2011, doctors are paid about $170 for the first time a patient has a wellness visit (coded G0438) and about $111 for subsequent annual visits (coded G0439), according to the American College of Physicians.

Patients should also be aware that some physicians do not offer the Medicare wellness visit at all. The law does not require them to. "Just as Medicare does not have the authority to tell physicians who they will treat, it does not have the authority tell a physician what services to perform," says Griffith of CMS. "As with any service, if a beneficiary's physician declines to perform the annual wellness visit for any reason, the beneficiary is free to seek care from another physician."

The Obama administration recently launched a nationwide campaign to raise awareness of the new Medicare benefits now available under the law. "Even in your 70s, 80s or beyond, you can reduce your risk of disability and chronic illness if you take care of yourself," CMS Administrator Donald Berwick, M.D., said. "With the new free annual wellness visits and free preventive care, people with Medicare have the tools to take commonsense steps to control their health."

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Patricia Barry is a senior editor with the AARP Bulletin.