There's two issues here. The first is that "as needed" is really hard for pharmacies and insurance companies to handle; the only way they can avoid arguments (

There's two issues here. The first is that "as needed" is really hard for pharmacies and insurance companies to handle; the only way they can avoid arguments (and potential lawsuits) is to dispense the maximum allowed. So even if your doctor expects that you're only going to need an 1 pill/day on average, if he writes "as needed up to 3 polls/day", you're going to be given 90/month. The second issue is deliberate overprescription. Most insurance companies have rules on the amount of medication which can be dispensed -- 100 days is a common limit, but some limits are as low as 30 days. The justification for this is that they don't want you to end up with lots of unneeded medication if your needs change; but usually the real reason is that they don't want to end up covering costs which can be offloaded to your next insurance company if you change insurers. In response, some doctors will deliberately inflate prescriptions -- e.g., if your doctor thinks you need one pill/day and trusts you not to abuse the medication, he might write a prescription for 3 pills/day so that your insurance company will approve an amount which will last you for longer.