I am an insulin using T??.
Last year I did a 5-day fast, as part of my exploration of keto lifestyle and for the experience / to see how I would feel [I am moderator of a keto group which has lots of people who experiment with fasting, so I wanted to actually experience fasting myself].
During the fast I still took plenty of non-calorific liquids, and salt. I use Levemir and Humalog insulins. I maintained normal activities during the fast (ie. work, chores etc) but did not try exercise other than walking.
Day 1 morning I took my usual Levemir. Day 1 evening I cut Levemir by about 20%.
Day 2 morning I cut Levemir by 50%. Same for Day 2 Evening.
Day 3 to Day 5 I did not take any insulin. I continued to closely monitor blood sugars.
End of day 5 I had a light dinner. I took 50% of usual night time Levemir. Day 6, back to normal insulin dosing schedule.
Some people say that they have lower insulin requirements after a fast. I didn’t experience that. I went immediately back to my regular dosing.
I did not have any lows during the 5 days and I felt fine. Blood sugars were in the 70 to 90s range mostly. Note: I had been eating keto for months already at that point and am pretty sure I was well keto adapted.
If you decide to fast, monitor very closely (blood sugar, and I’d recommend blood pressure too - though I didn’t). Keep up the electrolytes and fluids. Be ready to correct any lows with glucose / dextrose. If you feel at all unwell or “strange” be prepared to stop the fast.
I believe that fasting has a place in spiritual and health paradigms. However, it should be done with good preparation and understanding, treated with great respect, and stopped if necessary. There is a difference between slight discomfort / hunger and being masochistic / pushing through at the expense of health. Given you are diabetic, the preparation and care is even more important. I am not dissuading you at all! Just urging knowledge, preparation and caution.