When doing intermittent fasting, can I take a protein shake during fasting?

No. Fasting means no calories. A protein shake will spike your insulin. You could do 5 grams of BCAA powder, but that’s it. If you decide you need a protein shake, make sure it’s no carb and the lowest calorie per scoop you can find. Only use as much as you need, like a half scoop.

However, a low-carb protein shake is an excellent choice to break your fast.