The weight-loss area of the tax law offers guidance for restricted diets, says Mark Luscombe, principal federal tax analyst for Wolters Kluwer Tax & Accounting US. “That says if you are on a restricted diet for a particular disease and if you have a doctor’s certification that you should be on such a diet, you can treat it as a medical expense,” he explains.
…But claiming the tax break isn’t without hurdles. For starters, you must have certification from a doctor that you have a medically necessitated diet due to celiac disease, an autoimmune disorder in which the ingestion of gluten leads to damage in the small intestine. Going gluten-free as a beneficial lifestyle choice isn’t going to cut it.
The information is for the US only, but does provide which IRS documents to reference. I know Canada allows you to write-off a portion of medications, but I have no further details. In any case, the worst you can hear if you inquire is “no”.