I can't add any information beyond what Ken has related in his excellent post. I will point out that while each person is different in terms of becoming keto adapted, which I define as meaning that you are burning fat as your primary fuel, it also depends on where you start. If you are highly Insulin Resistant due to years of eating poorly with many processed carbs, adaptation will take longer. If you have been following a LCHF WOE for several months and want to go into ketosis by further lowering your carb intake, adaptation will happen faster. If you cheat or deviate from low carb periodically and you haven't been fully fat adapted yet, it will seem like it's never going to happen. The carb fueled metabolism doesn't want to let go of the ready energy source carbs supply. For me, being fully fat adapted for several months meant that it took a lot to, and I hate this term, "knock me out of ketosis." No two people will have the same experience, so assigning an average time to when adapting to ketosis should happen is not productive. Also, and this is my belief, getting a good quality blood ketone meter as opposed to keto urine strips or a breathalyzer, is a much more accurate way of confirming when you have a level of ketones (BHB) that indicates successful adaptation. Good luck.