You are under no obligation to disclose your medical condition to your co-workers even if you disclose your condition to your employer. However, keep in mind the following:

• Your relationships with your co-workers may suffer if you start taking time off, or show fatigue or weight loss or other side effects without some reasonable explanation. 
• Disclosure may occur from a simple phone call or message from your doctor's office or if side effects occur such as weight loss or other physical changes, or fatigue. (Clothes that are suddenly too loose or too tight invariably lead to health questions.)
• It is stressful to keep a secret. The more important the secret, the greater the stress.

Co-workers are not obligated to keep your information a secret. Once you tell one person, keep in mind that news travels fast.

Choose carefully who, what, and when to tell.

• Once words are spoken, you can't take them back.
• If you are going to tell more than one person at work, start with the person with whom you feel safest. 
  • Consider setting one person as a point person you trust to tell other co-workers what is going on to save you from updating everyone. If you leave work temporarily, the same person can keep you up-to-date about what is happening at work.
• The timing is up to you. If you need an accommodation at work to help you do your job that will seemingly make you "special" or move more work to co-workers, it may be useful to tell co-workers once the accommodation has been agreed upon with your employer. 

If you do disclose your condition, tell people what to expect. 

For additional information, see:

• Should I Disclose My Condition To Co-Workers?
• What Should I Tell Co-Workers?
• How Should I Handle Inappropriate Questions?
• What If A Problem Arises With A Co-Worker?

Whether you tell or not, start keeping a work journal about events at work that either show how well you are doing your job or that could seem to be discrimination or harassment.

NOTE: For information about disclosing to your employer, click here. 

Think through the advantages and disadvantages of telling co-workers.

Perhaps you only need or want to tell the people who work most closely with you because it will be difficult to hide your symptoms or because you'll need an accommodation that will raise questions and possibly even result in a greater workload for the person. It you only want to tell one person, and you think that person can keep a secret - great! But, if not perhaps it would be better if the news came from you.

Experience has shown the following are advantages and disadvantages to disclosing a health condition to co-workers. Add your own to the list before making a decision.

Advantages:

• Keeping secrets is stressful.
• You have an opportunity to control the information and avoid the rumor mill with potentially crazy rumors. In most work settings, nothing stays secret for very long. 
• If you need an accommodation, it explains what is happening. Otherwise, resentment can build up because you're being treated as special.
• You may get a great deal of support.
• You may be able to speak more openly about any issues that arise, including changes in your health.
• You won't have to worry about people who work with you finding out about your diagnosis.
• You can take your drugs and other treatments without having to hide them. (Be cautious if you use marijuana for health reasons even if it is legal in your state. Because it is illegal on a federal level, the Americans With Disabilities Act and similar laws may not protect you from being fired for using illegal drugs.)
• When people tell about a medical condition, they tend to learn that similar things happen to everyone. Once you open up, people tend to open up in return. Not just about a health condition -- but about all sorts of things.

Disadvantages:

• It is impossible to predict how people will react.
• People who react positively initially may change their attitude over time.
• People may start treating you differently. They may show pity. At the other extreme, they could even start harassing you, even though it is illegal under the Americans With Disabilities Act and similar laws.
• Competitors may try to use your health condition to their advantage.

If your employer reacts poorly to your medical condition, you may find that there are subtle or not so subtle changes in your relationship.

Secrecy is often confused with toughness, and some of us see toughness as a virtue.

• You may feel that you are being treated differently, or that you are no longer being judged on your performance, but by your diagnosis.

Co-workers are not required to maintain the confidentiality of personal or medical information that you disclose to them.

Consider asking your employer to educate your co-workers about your disease as an accommodation.

Tell people as much or as little as you like. 

• At least give people an idea about your diagnosis and your treatment, as well as how your condition and/or treatment will affect your work so they know what to expect. 
• Just as with your employer, it is important to manage co-workers' expectations. Be sure to let them know that a diagnosis is fluid. What you know and share today is not necessarily what will be true in a month, or six months or a year from now. A discussion of a health condition is not like talking about leave to have a baby where there are usually clear dates and an understanding of what will happen. It is not possible to predict what will happen to any particular person with a major health condition. Let co-workersr know that you will keep them to date as things progress.
  
• The more you tell people about your condition, the less afraid of it they will be.
• If you decide to keep the information to a minimum, be prepared for additional questions. You can always tell more information later if things change.

Always prepare what you will say before you tell people about your health condition.

Let people know that your health condition does not change who you are or what you can do.

Play out in your head the different possible reactions and what to say or do.

Speak out if someone offends you. When people are being insensitive, let them know.

Realize that another person's reaction likely has more to do with the illness and the shock rather than you. Many people are afraid of your illness and their own vulnerability. The news may trigger their own pain or fears of mortality.

Keep in mind that the person is not trying to be rude or inconsiderate. 

If the person is misinformed, educate them about your condition and prospects. Let them know that it is not a death sentence.

The more you talk to other people about what you are going through, the more comfortable they will feel with you and their fears about their own mortality.

Encourage people to ask the questions that are on their minds. Don't be surprised if they have difficulty wording their questions. 

It may be especially helpful to co-workers to explain what you have learned about your illness. It will help take their personal fear away.

NOTE: It may prove helpful in the future if you keep notes about inappropriate questions at work in a Work Journal.  The journal should also include information that could be used if you ever want to file a discrimination claim or stop working because of your health condition. For information about your rights with respect to discrimination, see the Americans With Disability Act.

If a problem arises with a co-worker, try to resolve it face-to-face. Perhaps all the person needs is education, such as:

• Education about your health condition. Many diseases are a rumor filled mystery to people. A little education can dispel the myths.
• That your condition cannot be transmitted at work so the co-worker doesn't have to fear. If your condition is transmittable, point out all the steps that are being taken to be sure that it doesn't happen. For instance, the odds of transmitting HIV in the normal workplace are almost infinitesimal. Even in a risky setting like a surgical room, precautions can be taken.

If a talk doesn't work, get help. Talk with the Human Resources department or with your manager. This isn't personal -- it's a work issue.

If the problem rises to the level of harassment, you may be protected under the Americans With Disability Act. If so, follow the steps described in the article: Discrimination.