You should definitely make it a priority and let the p-doc know that it is your priority. There are weight-neutral medications. Stay clear of the worst offenders such as Zyprexa, Seroquel, Depakote... but even more benign medications (benign in general, as measured by effects on groups of people) can give YOU a weight gain so you will need to be careful.

I polled people here about the worst medication side effects and weight gain came out on top, mentioned by close to 50% of respondents.