The new health reform law is expected to create 32 million more insured Americans, according to the Congressional Budget Office. The federal government plans to expand Medicaid to low-income adults and subsidize purchases on the health-insurance exchanges when it requires most Americans to carry insurance in 2014.

Maine will have 81,000 more insured residents because of reform, according to an Urban Institute analysis. An insurance card, however, will not mean much to patients if they don’t have access to providers to care for them.

A primary-care physician is the first contact for people with undiagnosed illnesses. They include family physicians, pediatricians and internal-medicine doctors. Primary-care physicians’ share of the U.S. health-care dollar is only 7 cents, but they control 80 cents of the health-care dollar by sending their patients to hospitals, referring them to specialists and handing out prescriptions.

The United States has about the same number of physicians per capita as other industrialized nations, but the nation has far fewer primary-care physicians than specialists. Primary-care physicians make up about 50 percent of the physician work force in most other developed nations, compared with 35 percent in the United States.

Specialists here also earn as much as three times more income than primary-care physicians, which helps explain why the number of specialists per capita has risen dramatically since 1965, while the ratio of primary-care physicians has remained relatively constant.

The outlook is for more of the same: greater scarcity of primary care physicians and a growing supply of specialists.

Massachusetts reformed its state health-care system in 2006, giving the nation a glimpse of what is to come when access to health insurance is expanded without expanding the supply of primary care.

The average wait for a non-urgent appointment with an internist rose from 17 days in 2005 to 48 days in 2011. Less than half of family physicians there are accepting new patients, compared with 70 percent four years ago.

Massachusetts has about 108 primary-care physicians for every 100,000 residents, compared with 111 per 100,000 in Maine.

The primary-care workload is expected to increase by nearly 30 percent by 2025. A number of factors feed this demand, including a growing population, a flood of baby boomers becoming Medicare beneficiaries and acquiring medical conditions as they age, and the newly insured because of the reform law.

The supply of primary-care physicians, however, is expected to rise by only 2 percent to 7 percent. Three out of 4 physicians say they already are at or over capacity. The math screams that there will be a crisis of health-care access in the next 15 years. We can expect longer waits for appointments, shorter physician visits, greater use of nonphysicians for routine care and higher prices.

The U.S. trains about 16,000 doctors a year. The nation would have to increase that number by 6,000 to 8,000 annually for 20 years to meet expected demand.

Adding to the sense of urgency is the fact that about one out of every four Maine physicians is at least 60 years old.

About 4 percent of Maine residents live in federally designated primary-care shortage areas. Physicians tend to cluster in areas where supply is already high, rather than where the need is greatest. About 80 percent of new physicians in the 1980s and 1990s did this.

Physicians like affluent areas with well-insured patients, high-tech hospitals and civic amenities that offer a better quality of life. These high-income enclaves are also home to the nation’s healthiest people.

Most people do not want to recognize that health care is rationed and has been by lack of insurance. Health reform is expected to rectify that, but it will exacerbate a new form of rationing: The doctor is not in.

Steve Jacob is a veteran health-care journalist and author of the new book, “Health Care in 2020: Where Uncertain Reform, Bad Habits, Too Few Doctors and Skyrocketing Costs Are Taking Us.” He can be reached at steve@unitedstatesofhealth.com.