Many Medicare drug plans place restrictions on certain medications. You can find more information on restrictions for your prescriptions by clicking on the Medicare tab to the left of the prices on any drug page.
Some drugs on Medicare have quantity restrictions, i.e. you can only buy 30 pills in a 30-day period. GoodRx will tell you those quantity limits. If you choose not to use Medicare to make your drug purchase, you will not be limited by these restrictions.
Some drugs on Medicare have prior authorization requirements—basically, your Medicare plan won't cover your prescription until it is approved. If you choose not to use Medicare to make your drug purchase, you will not be limited by these restrictions.
Many drugs on Medicare have step therapy requirements, which means your Medicare plan requires you to first try certain drugs to treat your medical condition before they will cover another drug for that condition. If you choose not to use Medicare to make your drug purchase, you will not be limited by these restrictions.
Sometimes Medicare plans will make exceptions to these restrictions; you'll want to check with your plan to be sure.