Nutrition Tips for People Living with Celiac Disease Long Term 

I found lentils have to be picked over to check for other grain contamination. Even ones labelled GF sometimes have an issue. www.glutenfreewatchdog.org/news/general-product-warning-check-your-lentils-including-certified-gluten-free-lentils-for-foreign-grain/

You can find GF lentils easily on line. As an alternative, place your lentils on a baking sheet and visually inspect them or foreign grains. Once you have done this, rinse them and you are good to go!