How long can I take phentermine for?

Phentermine is a potentially habit forming prescription medication and it is only advised that it be taken for a period of three months, a recommendation that is based on original drug trials whereby participants were monitored over a three month period taking phentermine. However, in some US states, doctors are able to prescribe phentermine for longer periods, or to prescribe it several times within a certain period with month-long breaks between each period.