Water fasting is not only safe, it's an incredibly satisfying experience, IF you replace your electrolytes.
To anybody that does not have previous experience fasting i strongly recommend starting slowly.
Spend the two weeks on a 16 hour fast (called 16/8). You fast for 16 and eat during 8 hours. You can eat anything you want but you cannot eat outside those hours.
After 2 weeks of that move to a 20/4; eat all your daily nutritional requirements in a 4 hour window. Maybe at this stage you'll need to not eat some sweet stuff in order to make room for your lunch and dinner. The choice is yours, but it would be folly not to eat your minimum nutritional intake.
After 2 weeks on 20/4, move to 23/1 and remove all sugars from your diet. You won't have time to eat them anyway! Bear in mind that simple carbohydrates (white bread, white pasta... Anything made from refined flour) is also a sugar. So is fruit. No fruit. No sweets. Only wholegrain /brown bread, pasta, etc.
I know it sounds difficult to do but once you've completed the first 4 weeks you'll be well accustomed and not have any problems. After 3 weeks on 23/1, if you are not in Ketosis you could then do a 4 or 5 day fast, consuming half teaspoon of salt and one teaspoon of potassium chloride (aka LoSalt / NuSalt) in a glass of water each day. This will keep your electrolytes in balance.
When ketosis kicks in you'll know all about it. Your body will now be creating more than double the amount of energy it normally produces. You will not be able to sit still. You will be very active. You will feel like a million dollars. You will feel invisible, like you can do anything (and you probably will). To the describe the sensation as euphoric would a colossal understatement.
My name is Barry and I have been experiencing ketosis for 4 months now. I've learnt allot, am still learning. I want to help. Klar feel free to contact me again.
PS. If you're taking any medication, stay on it and consult your doctor. Let them know you're going to fast.