Your blood Sugar is as it should be: low, because you are in ketosis and living from your fatty acids. The Nurse will only know about blood Sugar readings while you are eating, where your main fuel is glucose.

For example, by the third day of water-only-fasting, ketone production is sufficient to provide nearly all the energy the body needs while at the same time your body's protein begins to be strongly conserved. Your body will still need a tiny amount of glucose for some functions, however, so a very small amount of protein, 18-24 grams, is still catabolized to supply it - from 1/2 to 1 ounce of muscle tissue per day.
Over a 30 day Water Fast a person generally loses a maximum of 1-2 pounds of muscle mass.
At any one time we only need about a teaspoon of Sugar to maintain blood glucose for the maintenance of the Brain and other essential organs/processes while fasting and this supplied internally during ketosis and Autolysis.
You are burning fatty acids and not glucose/sugar, so your blood sugar will be low as expected and normal for everyone in the fasting process.

Nothing to be concerned about whatsoever.

Chrisb1.