Most of us think of health in black-and-white terms: we’re either healthy, give or take a few bouts with a cold, or too disabled to work. But a huge number of Americans fall in between. According to a study by the RAND Corporation, 120 million people, or 45 percent of Americans, suffer from a chronic illness such as diabetes, hypertension, asthma, or cancer (for survivors, the aftereffects of surgeries, treatment, and medications can linger for years). And about half of these have multiple chronic conditions.

What’s more, autoimmune disorders like multiple sclerosis, scleroderma, and inflammatory bowel disease “tend to strike women age 25 to 40, which are the prime careerbuilding, childbearing years,” points out Rosalind Joffe, founder of cicoach.com, a Newton, Massachusetts- based firm that helps people living with chronic illnesses continue their careers, and the author of Women, Work, and Autoimmune Disease: Keep Working, Girlfriend!

Joffe, who was diagnosed with multiple sclerosis at age 28 and knows firsthand about the effects of chronic disease on one’s career, offers these tips on coping with illness without killing your career.

1 Communicate with care. Women tend to be more open than men about discussing their health in the workplace, but this can backfire if they’re judged as using an illness as an excuse to shirk their jobs. “If an illness is not affecting your job performance, there’s no reason to discuss it,” says Joffe. However, if your health is starting to have an impact, she suggests speaking up and demystifying the situation before your supervisor and coworkers jump to their own conclusions.

It isn’t necessary to name your disorder. “Talk about the effects of your condition on your body and what you’re having trouble doing,” says Joffe. “Make it clear that you’ve got things under control and are not leaving it up to someone else. Be proactive and positive. And don’t become emotional; no one wants to hear a sob story.”

2 Request reasonable accommodations. Figure out in advance what you need in order to get your job done, whether it’s a few 15-minute breaks throughout the day or extra time off for medical appointments. Joffe says the best accommodation is flexible working hours. Take advantage of technology: you can check e-mail from a doctor’s office via your Blackberry or use voice recognition software if typing becomes too difficult. If you’re a senior level executive, see if you can delegate tasks to your subordinates.

3 Evaluate whether you can continue to do your job. If your present job or career is no longer doable, you may need to shift gears. One nurse Joffe coached switched to teaching nursing students, and a lawyer who can no longer handle the stress of courtroom litigation could practice law in an office environment.

4 Be your own boss. Owning your own business means you can set your own hours and implement accommodations without having to seek anyone’s approval. If you’re currently employed by someone else, striking out on your own in a homebased business is tempting, but Joffe advises caution in today’s economy. You need to evaluate if you have a sellable idea or skills, are highly motivated to be self-employed, and can afford the costs of setting up a new business. “Don’t jump into self-employment just because you have a chronic illness,” she warns.

5 Make sure you’re covered. Health insurance is a huge stumbling block for the self-employed. Unless you can get benefits through your spouse, insuring yourself is usually significantly more expensive than getting covered through an employer’s plan. Also, while some state laws guarantee coverage to everyone, in others insurance companies can reject applicants with pre-existing conditions.

Despite the setbacks and stress, Joffe says work can offer sufferers of chronic disorders a sense of accomplishment and purpose. “Workplace success in the face of illness is transforming,” she says. “It gives you the power and the confidence to face other challenges large and small.”