BOULDER, Colo. - With its excellent public services, rich cultural offerings and fall afternoons that glisten like gold in a prospector's pan, it is no wonder that this outdoor-recreation mecca has also become a retirement paradise.

But for transplanted and local retirees alike, getting to see a doctor can be even harder than registering for one of Boulder's overbooked computer classes for seniors. Medicare cards, long considered a guarantee of health care in old age, are proving little better than fool's gold.

Because the Medicare program has reduced the amount it reimburses doctors, many seniors now have to make as many as a dozen phone calls just to find a physician who is still accepting new Medicare patients. Others were dropped by their longtime doctors when they turned 65.

"Seniors are going without care, and patients are getting sicker," said Jim Peters, vice president of Boulder Community Hospital. "We are close to a crisis."

Colorado is one of the more extreme examples of a trend that is sweeping the country and threatening to undermine Medicare. Many Medicare cardholders have supplemental insurance for prescription drugs and other uncovered expenses, but since its enactment in 1965, Medicare has provided basic health benefits for all senior and disabled Americans.

Until now, at least. The aging of the population - combined with escalating health-care costs, cuts in Medicare reimbursements, problems with Medicare HMOs and political gridlock in Washington - is producing a physician shortage so severe that social service agencies in some communities now count Medicare beneficiaries with the homeless and the uninsured as being "medically underserved."

The nonpartisan Center for Studying Health System Change recently found that about one in nine Medicare beneficiaries reported delaying care or being unable to find a physician last year - before this year's 5.4 percent cut in physicians' fees took effect.

And with the announcement expected soon of a 4.4 percent cut for next year in Medicare payments to doctors, the situation is likely to get even worse.

"If Congress does not reverse the cut, you will see a perfect storm," said Dr. Jeremy A. Lazarus, a psychiatrist and president of the Colorado Medical Society. "Physicians will stop seeing even current Medicare patients."

A bill to restore billions of dollars in reimbursements to doctors is pending in Congress, but action this year appears unlikely.

Lawmakers focused their election-year attention on demands by the 35 million-member AARP and other senior groups that Medicare begin covering prescription drugs. But the Senate could not agree on the details of a drug benefit, and when lawmakers in mid-October appeared on the verge of reversing some of the fee cuts for doctors, Sen. Olympia J. Snowe, a Maine Republican, prevented her colleagues from doing one without the other.

The action left many Colorado physicians shaking their heads.

"We're not talking about big money compared to a prescription drug plan," Denver geriatrician Christopher Unrein said of Medicare reimbursements. "If you don't have someone to write the prescription, what good does a benefit do you?"

Seniors' representatives and patient advocates know the problem is real.

Vi Bowers, slight but sharp in her blue AARP vest, recently had a hard time finding both a gynecologist and an ophthalmologist in the Denver suburb of Wheat Ridge. Three or four gynecologists' offices told her they were not accepting new Medicare patients. Finally, she persuaded a friend's doctor to take her.

But now the 75-year-old is afraid her new doctors will drop her.

"You've got to be careful not to step on your doctor's toes," Bowers said. "They don't want to mess" with Medicare because of the low payments.

The Denver offices of Colorado Patient Advocates, the Boulder County Medicare ombudsman's help line and the private Colorado Gerontological Society are all fielding more calls from Medicare beneficiaries unable to find doctors or pay for their prescriptions.

Eileen Doherty, executive director of the gerontological society, recently asked about 100 seniors attending a Medicare meeting in suburban Littleton how many had a regular doctor.

"Only one person raised their hand," she said. "When I asked how many have had trouble finding a doctor, about half the hands went up, and when I asked how many had to travel farther to get medical care, almost all the hands went up."

Some advocates say the problem seems to have stabilized after their groups surveyed doctors' offices and distributed lists of physicians still accepting Medicare patients.

But access often isn't there. According to recent surveys, only 4 primary-care physicians in 10 accept new Medicare patients in Colorado. In Colorado Springs - where a former judge, military retirees and leaders of prominent Christian ministries are among those unable to find doctors - the rate is closer to 1 in 10.

Increasing numbers of retirees are simply doing without a physician until they get sick. Hospital emergency departments are serving as de facto examination rooms for seniors, and many of the patients who arrive at the Penrose-St. Francis Senior Health Center have gone without health care for a while.

For many physicians, the math is fairly simple. In Colorado, private insurers reimburse doctors at rates often 25 percent above what Medicare pays for the same services. Faced with that, individual physicians and group practices have made a business decision that no more than some fixed percentage of their patients can be on Medicare. Many have reached their ceiling and are unwilling to take any more Medicare patients.

Of course, money is not the only reason doctors are dropping Medicare patients, physicians say. Paperwork hassles, complex billing codes and a "paranoia" about being accused of "fraud and abuse" also play roles.

In the end, however, "it's really the cost of medical care that creates the 'access' problem," said Dr. David Downs, president of the Denver Medical Society. As long as overhead and treatment costs climb while government reimbursement rates fall, he said, fewer and fewer physicians will treat Medicare patients.

Vicki Kemper writes for the Los Angeles Times, a Tribune Publishing Co. newspaper.