Does Medicare pay for tube feeding formulas? Yes, the formulas and supplies are covered by Medicare Part B and most insurance. Formula won't be covered unless it is the primary source of nutrition and you can't eat well enough to maintain your weight without it. Medicare covers tube feeding formulas if they provide all or the majority of your nutrition. Being able to swallow small amounts of food doesn't disqualify you, but if you still eat most of your meals and just use the tube feeding as a supplement or convenience, Medicare won't cover it.
A form/documentation by your doctor is required for Medicare reimbursement and a diagnosis of ALS covers all the requirements.
Standard tube feeding formulas are covered as well as special formulas needed by diabetics, kidney or liver patients, etc. (Do an internet search for Medicare Part B Enteral Nutrition Reimbursement Manual.pdf. It lists many but probably not all covered formulas.) "Natural" formulas may be covered if your doctor documents an allergy or intolerance of standard formulas. A simple preference for a natural formula isn't covered. The cost of foods and supplements used to make your own blenderized formula is not covered.
As others have said, typical DME providers may not deal with formulas but pharmacies and other outlets may be approved DMEs. Your doctor's office should take care of sending the order to a provider.
If you get formula through a Medicare provider, compare the amount of your copay against the price you would pay buying it yourself online - no prescription needed. Often prices are so jacked up by Medicare approved providers that you end up paying more copay even after Medicare limits the amount Medicare will pay. The provider ends up being paid by Medicare and then again by you, sometimes as much as being double paid the actual cost! Self pay may actually be cheaper if you do some comparison shopping online. It does get expensive but that should be offset by lower grocery bills and a small Medical deduction on your taxes. In fact, I am surprised that Medicare does pay for generic formulas. They certainly don't pay for anyone's groceries!