NEW YORK (CNNMoney.com) -- As a 21% cut in Medicare payment rates to doctors took effect Monday, eight of the 15 patients on Dr. William Schreiber's schedule are on Medicare.
"I'm stuck," he said.
"I have to see them. I don't have a choice" said Schreiber, a primary care physician based in North Syracuse, N.Y. "It's not a case of closing my doors to Medicare to get back at someone for cutting my salary. It's a case of economic survival."
Shreiber's eight patients are lucky, for now. Many doctors around the country are either not accepting new Medicare patients or dropping their Medicare patients altogether.
Physicians say they are shunning Medicare because they are tired of dealing with the yearly threat of a payment cut under federal law requiring that reimbursement rates be adjusted annually based on a formula tied to the health of the economy.
Patient advocacy groups say this growing doctor boycott against Medicare is a big concern to senior citizens. Some 43 million Americans currently receive Medicare coverage.
"There's no question that a long-term solution to this situation is needed," said Marc Steinberg, deputy director of health policy with patient advocacy group Families USA. "The system that's in place doesn't create the stability that you want in a rational heath care system."
The AARP, the largest membership organization for people 50 and older, said a physicians' Medicare boycott is top-of-mind for its nearly 38 million members.
"From our perspective, the uncertainty about how much Medicare will pay doctors every year is contributing to doctors not taking new Medicare patients," said David Allen, spokesman for the AARP.
"You already have a hard time finding a doctor if you are on Medicare," said Allen. "Can you imagine the difficulty if your doctor drops you and you have to find a new one?"
Especially threatened by this backlash are baby boomers on the cusp of becoming Medicare-eligible, said Allen.
Another 7 million Americans will become Medicare eligible over the next five years, according to the Center for Medicare and Medicaid Services (CMS).
"You have to replace this current [Medicare reimbursement] formula," said Allen. "It's flawed. You need a system that pays doctors fairly."
Until that happens, doctors say Medicare beneficiaries should prepare themselves in case they find themselves shut out.
Doctors and other health experts say there are things patients and their families can do in the event their doctor opts out of Medicare.
Ask for referrals: Doctors who drop Medicare patients typically have to give sufficient notice to their patients -- typically four weeks -- that they are changing their policies.
Also, it's good practice for doctors to provide patients with references for other doctors who are taking new Medicare patients, said Dr. Lori Heim, president of the American Academy of Family Physicians (AAFP).
Heim said patients can certainly ask their doctors for referrals as well as for lists of government or other medical groups in their state.
Also, get a copy of your entire medical record. Some practices can charge 75 cents per page of your record.
But doctors are not legally allowed to withhold the records if you can't pay the charge, according to Joel Greenberg, health law expert with the firm of Abrams, Fensterman, Fensterman, Eisman, Greenberg, Formato & Einiger, LLP.
Be aware of "patient abandonment" laws: This applies not just to Medicare patients. Greenberg said most state licensing laws say it is unprofessional conduct to just "abandon" a patient without sufficient notice.
"Abandonment means a physician terminates the treatment of a patient without adequate time for the patient to transition care to another appropriate physician," said Greenberg.
Further, Heim said abandonment is applicable to a patient who has seen the doctor just once or repeatedly. If a doctor is found to have abandoned a patient, then the state can either suspend or revoke a doctor's license, said Greenberg.
Access urgent care centers: These are typically free-standing health clinics or associated with a hospital.
"These may be a good stop-gap option for Medicare beneficiaries who have lost their doctors until they find another," said Heim. However, she said these centers should primarily be used for urgent care, since they are not set up to develop an ongoing relationship between doctor and patient.
Use of emergency rooms: For an emergency, go to an ER. "But this is not where you go to get your blood pressure checked and managed," Heim said.
Schreiber warned that as more doctors stop taking Medicare, it will "inevitably lead to an abuse of the ER."
"We don't advise these for anything other than simple acute problems such as a sore throat," said Heim. "These clinics are not for treatment of chronic issues that elderly patients face."
Pay out of pocket. Most patients don't want to lose their doctor, so they will try to pay out of pocket, experts said. But this option is complicated, said Schreiber.
"If I have decided not to take any Medicare patient, I can't also knowingly take a new patient who I suspect is on Medicare but is willing to pay out of pocket," he said.
Despite the loss in income, Schreiber said he will continue to see Medicare patients for now, since they account for 30% of his business.
Facebook founder Mark Zuckerberg called President Obama to tell him the latest NSA disclosures are frustrating. More
Seeking: web developer, marketing associate, and budtender. More
From fewer police to cuts in healthcare benefits and monthly pension checks, Detroit's workers, retirees and residents share how their lives have been changed by the largest municipal bankruptcy in history. More