Water fasting

My question is, is it safe for me to go on a 21 day Water Fast (I did a lot of research, I feel like I pretty much know what I'm doing) if I can't have medical supervision? In my country doctors are very very against Water Fasting because they never even really heard about it, plus there's a high chance of getting ill because of the lack of hygene in hospitals. I don't really want to risk it, so if I eat very nutritious food (main attention on potassium) and take vitamins before the fast and I'm a 21 year old healthy woman, can I die or get sick on a 21 day water fast?
(I also have enough body fat.) Tweet