To be fair to everyone, I think Law2Doc is responding to the OP considering the layman's definition, since the OP didn't clarify how he was using the term. ADeadLois, bbas, and I are using the psychological definition.
Regardless, I think that if someone really is withdrawn from society and cannot properly function in a clinical setting with patients, medicine might not be a good idea.
If someone is just shy and quiet, or less inclined to seek social stimulation, or however we want to define our terms, then medicine may be a good career match if in a patient situation, they can ask and answer questions and do whatever else is required of a physician in a clinical setting.