" All types of fasts can have therapeutic benefit. The key to therapy is prolonged therapeutic ketosis (blood ketones in the range of 3–6mM), together with reduced blood glucose levels (3–4 mM). Patients will need to use the Precision Xtra meter from Medisense to determine when they can enter the therapeutic zone. GKI ratios of 1.0 of below would best represent the therapeutic range. Intensive "

― Jason Fung , The Complete Guide to Fasting: Heal Your Body Through Intermittent, Alternate-Day, and Extended Fasting