You can purchase it anywhere but it must be fresh, and this cannot be guaranteed when you purchase it from the stores (you don't know how long it has been on the shelf). The best place to purchase it I was told is from www.barleans.com, because apparently they press it when the order comes in, and they fedex it to you immediately. I also believe they ship it for free if you tell them it is for cancer treatment. You should order the high lignan cold-pressed flaxseed oil. Once it is open you should keep it in the refrigerator always, otherwise if you order several bottles, they can be kept in the freezer for up to 1 year. It is very important the oils are fresh. I think you can also call in the order as well, as I did for my accountant, but I can't remember the telephone. There is an 800 number, they are located in Washington state I think. I believe you can get all info from their website. I think one 16 oz. bottle runs about $14-15 max.