Some illnesses are rather personal, like STDs. Others, like epilepsy would be one you ought to tell those close to you for obvious safety reasons.
I also look at illness/disease and telling others about them as opportunities for education The education that is received this way leads to increased tolerance.
Some diseases 'come' with an automatic, "I'm sorry, what can I do?" like cancer. Other diseases don't; but should. You're doing a great public service by saying how this disease alters your life (without writing a book about it).
Keep in mind, though" most people don't want to hear a litany and knock down drag out llst of your complaints. If you've been asked for theem, try to put a + spin on it.
If we had more potential educators about health, the cost woulld inevitably go down.