Thankfully those are normal. B12 was on the low end of the normal range when I first got diagnosed. When I last got it checked, it had come up a lot (455 last time checked).

You can search this site for prescriptions medications, but will need to know the manufacturer/maker if there is more than one, especially if you use a generic version of the medication: To see the ingredients you will need to click on the correct version of the medication and maker in the results, then scroll down to "Ingredients and Appearance" and click it, and then look at "Inactive Ingredients," as any gluten ingredients would likely appear there, rather than in the Active Ingredients area. https://dailymed.nlm.nih.gov/dailymed/  I didn't notice any gluten ingredients in Kirkland Almond non-dairy beverage, however it does contain Locust Bean Gum. Some gums may cause IBS-type issues in some people with celiac disease or gluten sensitivity:    

Have you had B12 levels checked?

For the past few months, I've been taking several supplements (a multi-vitamin, an iron supplement, a vitamin C supplement, and a magnesium supplement), all of which state that they are gluten free on the label.  

Maltodextrin is typically made from corn.