3 day fast advice

[Shopgirl2]

I'm planning to start a 3 day fast next week. Does anyone have experience with that length fast and can offer some advice? Did you take electrolytes, is there a good UK brand to use? Did you monitor blood glucose and ketones, and if so, what monitors did you use?
I've done 24 hour fasts, 36 hours and several 48 hour fasts before, so reasonably confident to try the 72 hour one.

I'm over 2 days into the fast now. I've had some electrolytes in water, which are gross, so just a small sip every now and then, and the water has to be refrigerated to make it taste less bad. Otherwise I'm mainly just drinking tap water. I miss eating food for the comfort it gives, but I'm not hungry in the way that makes you hangry, just I day-dream about food. My children stuck their Halloween sweets right under my nose, and they smelt nice but I wasn't in the least bit wanting to eat them. The egg they had for dinner, however, and cheese, has me salivating. I'm also dreaming of canned fish.
I was quite apprehensive about doing 3 days, but it's easy so far. I stopped eating at lunch time, so it's only 2 whole days without food. I am thinking of extending it by a few more hours so I have a little more time in stem-cell making mode hopefully.