I think the answer to your question may be different for different people. For those of us who are obese, I think we can likely fast a little longer before we start needing supplements.
I guess from the reading I have done, I think somewhere between day 3 and day 7 is where a significant percentage of people will feel better with salt, potassium and magnesium (please, no one use those specific ones as guidance, I’m going off memory here and have personally never done anything past 3 days).
I suspect (again, based on what I have read) anything much past 4 or 5 days and you might want to start being a little more careful when you break your fast.
What was your starting weight? Is the fasting being pretty helpful to you?
I really need to break this cycle of telling myself I’m going to fast and then some social thing comes up and I eat whatever everyone else is eating.
I’m almost 280 and I really think a good one for me would be 72 hours once a week and then OMAD all of the other days of the week.