My mother, who's a nurse, always says, "Self-diagnosis can be the best form of diagnosis."
That's not to say people can sense that they have cancer or a specific kind of illness, but that we generally know what's happening to our bodies.
For instance, a friend of mine complained of stomach pain for months, and every doctor she visited would prescribe her anxiety medication.
She told them that she felt some stress with her new job, but that it wasn't anything abnormal that would require her to take drugs.
After months of agonizing pain, it turned out she had a large colon polyp. Her recovery time was doubled all because doctors misdiagnosed her on several visits.
In my friend's case, she knew something was wrong, and that it wasn't anxiety. You'd think you would know that you're anxious!
Anxiety seems to be the diagnosis many doctors fall back onto. If a patient is displeased by that diagnosis, doctors will usually send them to see a specialist.
However, that may be too late in some cases.
Simon Willans complained to a doctor and nurse that he suffered from shortness of breath and dizziness, and was diagnosed with low blood pressure and anxiety.
He was told to come back in the morning, but that was too late...