Just use whatever your "official" scale says. If you weigh at the doctors weekly, then use that. If not, don't worry what the doctors scale says. All scales are calibrated differently and you can weigh something different on each one. Doctors are supposed to calibrate their scales regularly, but most don't and lot's of people weigh on them. Always weigh on the same scale, same time of day, same clothes, etc. for the most accurate gauge of weight loss.