Great qustion. No, a doctor's order is not required to purchase an Acapella or Flutter valve for home use. Different companies produce various models, and most should work equally well. As you mentioned, these devices are readily available over-the-counter at medical supply stores and online, including on Amazon. It's perfectly fine to buy them this way. However, a doctor's recommendation can be helpful to ensure the patient selects the most appropriate device for their needs. If insurance coverage is desired, a prescription from a doctor may be necessary. I hope this helps. John. community moderator.