Water Fasting Concerns 
It is not advisable to water fast under the conditions of hyperglycemia, hypoglycemia, schizophrenia or a chronic heart condition. If you have existing conditions it is best if you consult with a fasting expert and/or be monitored throughout your fast.  Be careful of dizziness and black outs. The heart is resting as much as it can during water fasting. Before you stand up, take one or two deep breaths to get the heart pumping. If you start to black out, sit down or crouch down on one knee. This will immediately stop the dizziness.