Hello #91053
I for one have not come across any evidence that low blood Sugar is any more of a problem on the Master-Cleanse or any type of juice fast in comparison to a water fast; after all on a juice fast you will still be feeding your body with glucose from the juices, and even to a lesser extent on the MC.
However, fainting (and other so-called symptoms of low blood sugar) such as the risk of fainting and blackouts, is minimized by not arising from a sitting position very quickly. This usually arises from a reduced blood supply to the Brain by a lowering of blood pressure, and is nothing to be overly concerned about, as long as you follow the above advice.
You may find this previous link to be helpful here..........