There are several reasons why a prescription for a controlled medication may only be for one month. Your doctor may have specified this amount for each refill, or the pharmacist may believe it is safer to only dispense a month's supply to reduce risks such as a child finding the medication or it getting lost or stolen. If you have insurance through the government, you should not have to pay more for your medication. It is recommended to discuss this with your pharmacist to get more information on the situation.