Water fasting is safe for most people when done correctly. Problems arise when people go too long early in their fasting experience, improper hydration, and improper refeeding. Start with short fasts when going unsupervised. Few people can manage 30-40 days their first time. A series of 1-3 days, working up to 10 days is best. Be careful to stay hydrated, but don't overdo the water either. Drink 1-2 quarts (or liters) a day throughout the day-not all at once. Avoid caffine in any form.