By N.R. Kleinfield, New York Times News Service

His work was good. He hadn't socked the boss or embezzled money. It had to do with what was inside him: diabetes.

UPS framed it as a safety issue: Steigauf's blood sugar might suddenly plummet while he tested a truck, causing him to slam into someone.

Steigauf considered it discrimination, a taint that diabetes can carry. “I was regarded as a damaged piece of meat,” he said. “It was like, “You're one of those, and we can't have one of those.”

With 21 million American diabetics, disputes like this have increasingly rippled through the workplace:

• A mortgage loan officer in Oregon was denied permission to eat at her desk to stanch her sugar fluctuations, and eventually was fired.

• A Sears lingerie saleswoman in Illinois with nerve damage in her leg quit after being told she could not cut through a stockroom to reach her department.

• A worker at a candy company in Wisconsin was fired after asking where he could dispose of his insulin needles.

In each instance, diabetics contend that they are being blocked by their employers from the near-normal lives their doctors say are possible. But the companies say they are struggling, too, with confusion about whether diabetes is a legitimate disability and with concern about whether it is overly expensive, hazardous and disruptive to accommodate the illness.

The debate will probably intensify. The number of diabetics in America swelled by 80 percent in the past decade. Experts say the disease is on its way to becoming a conspicuous fact of life in the nation's labor force, raising all sorts of issues for workers and managers.

Even an outspoken advocate for diabetics like Fran Carpentier, a Type 1 diabetic and a senior editor at Parade magazine, understands the implications for business. “Knowing what it's like to live with the disease hour by hour, day by day, I wonder if I owned my own company if I would hire someone with diabetes,” she said. “I'm being bluntly honest. And it kills me to say this.”

Doctors, though, say that with improved medications and methods of self-testing blood sugar, most diabetics can do almost any job if they properly manage their illness. Yet myths about the disease persist, advocates say, leading many companies to shun diabetic employees.

Part of the confusion is a byproduct of the disease itself, a capricious illness of elevated, damaging levels of sugar in the blood. Type 1 is a malfunction of the immune system that usually appears in childhood, while the far more prevalent Type 2 is closely associated with obesity and inactivity. Many people with diabetes will face withering complications like blindness, amputations and heart disease. Others will not.

For some, particularly insulin users prone to the abnormal drops in blood sugar known as hypoglycemia, the illness can cause dizziness, fainting or muddled judgment. Doctors, however, say those constitute a tiny number of readily identifiable cases.

Nonetheless, the risk of plunging blood sugars has fueled a long-standing reluctance to employ diabetics in jobs like those of truck driver or police officer, if they are on insulin.

Federal law bars diabetics from joining the armed services and prevents diabetics on insulin from becoming commercial pilots.

Innumerable diabetics, though, are engaged in more mundane jobs uninvolved in matters of life and death. For these people — secretaries and factory workers and programmers — a “reasonable accommodation,” like permission to eat at one's desk or to be excused from fluctuating shifts, can make the difference in whether they can function.

When disputes can't be resolved, the cases often land in court or before the Equal Employment Opportunity Commission. The commission, which enforces the Americans With Disabilities Act of 1990, says diabetes-related complaints have been on the rise, one of the few conditions generally showing an increase in complaints. Diabetes accounts for nearly 5 percent of the 15,000 annual allegations that the commission gets under that act, trailing only back impairment, other orthopedic injuries and depression.

Often the courts are of scant help in bringing clarity. Judges in nearly identical cases have ruled in completely opposite ways, leaving diabetics bewildered and businesses unsure what, if anything, they should do.

The quarrels are as varied as working life: a musician rejected for a cruise ship's cabaret band, baggage handlers and plane cleaners fired by an airline, a blackjack dealer dismissed by a casino.

The American Diabetes Association fields about 100 calls a month about workplace tussles like these. Many of them revolve around accommodations, though the changes sought tend to be modest: predictable hours, a place to test blood, freedom to snack when sugars get unbalanced.

There has been progress for diabetics: the San Antonio Police Department's barring of diabetics on insulin was struck down. Insulin-using diabetics in good control of their illness can get private pilot's licenses.

Employers, however, prevail in a vast majority of cases. (Many are settled.) It is hard even to get lawyers to pursue complaints, since prejudice is tricky to prove. Establishing discrimination has become harder since 1999, when the Supreme Court held that if a disability can be corrected with medicine or things like prostheses, it is not necessarily protected. Advocates for the disabled say the ruling warped the intent of Congress.

Ruth Colker, a law professor at Ohio State University who studies disability discrimination, said that very few working people with diabetes now find themselves guarded by the law.

Wary of bad outcomes, many diabetics conceal their illness on the job. Brian T. McMahon, a professor at Virginia Commonwealth University who studies workplace discrimination, said: “You get to the question of whether or not to disclose you have diabetes. Most people opt not to, for they fear: Am I inviting more trouble?”

There was a time, four or five decades ago, when you wouldn't find one diabetic on the entire floor of a factory. Now, Type 2 diabetics are commonplace. It is not only the ascendancy of the disease, but also the fact that a condition once considered a corollary to old age is striking people sooner, catching them long before retirement. And this comes as companies are already struggling to balance productivity in the workplace with soaring medical costs.

To understand the brutal math of diabetes, all a business has to do is consult the Web site diabetesatwork.org, set up by the government to furnish advice on addressing diabetes in the workplace. One of its tools is a calculator that uses rough assumptions to suggest what costs might be involved.

Businesses plug in the number of employees, the tally is multiplied by 8.2 percent (a slightly dated national prevalence rate for diabetes), then that figure is multiplied by $13,243, an estimate for yearly medical costs of a diabetic. Voila: the price tag of diabetes. It is a burden more than five times that of workers without diabetes.

Ron Z. Goetzel, a vice president for Thomson Medstat, which analyzes health-care costs for businesses, said that if absenteeism and productivity losses are added, diabetes ranks third among major conditions as an economic cost to employers, after heart disease and hypertension.

Companies have only started to reckon with this and with the disease's ancillary concerns. Even if advocates say safety is rarely a factor, companies argue they cannot take chances with some types of workers, like school bus drivers or even pizza delivery men.

Concessions may seem small — for example, granting a bank teller more frequent breaks — but many employers contend that if rules bend for one person, that breeds resentment among other employees. Co-workers cannot see the diabetes, and if an employer gives preferential treatment to a diabetic worker, it cannot legally tell other workers it is because of the diabetes. Companies feel that indulging all diabetics trivializes the meaning of disability and of fairness.

In addition to the threat of a suit under federal or state disability law, businesses must grapple with the Family and Medical Leave Act, which requires them to grant unpaid leave to ill workers. That can create scheduling difficulties.

“This whole area gets complicated, because the medical leave act can mean employees absent from the workplace for extended periods,” said Stephen A. Bokat, general counsel for the U.S. Chamber of Commerce. “That bothers employers even more than an employee needing a half-hour during the day to administer some insulin.”