@beejenigma I'll try to explain why, based on lengthy study of the Medicare rules and a long discussion with my excellent independent pharmacist about how it all works.

Any medication dispensed via durable medical equipment (nebulizer) is covered by Medicare Part B. Many pharmacies seem to not be aware of this, and try to submit to Part D, which always rejects. (It seems that not every pharmacy is enrolled to dispense under Medicare Part B, but this is my impression.)

Saline nebs are considered an "adjunct treatment" not a medication. So if you have been prescribed a nebulizer and an inhaled prescription medication, when saline is also prescribed it can be covered. The pharmacy must code the bill correctly and submit to Medicare Part B. It also helps if the prescription for the nebulizer is in your Medicare records.

If you do not have any prescribed nebulized medications, it is unlikely Medicare will cover the saline. However, if you already use a prescription inhaler for your lungs, if the doctor prescribes the inhaled version of the same drug, then the saline, it will be covered. My doc did this - I normally only use an inhaler, but I have an "on hand" nebulized version of the same, for use during an exacerbation.

For those with a Medicare supplement that includes a monthly or quarterly allowance for over-the-counter FSA eligible products, the saline solution meets the requirement.