The whole "keto flu" is skippable when carbs are gradually reduced for the first couple weeks instead of going cold turkey plus assistance from MCT oil and exogenous BHB to kickstart ketosis. My shift into ketosis was quite easy and painless using that strategy.

Those BHB salts also help with the electrolyte loss that is a major cause of the "flu". Even after the transition you'll need to maintain a high sodium diet as without the carbs you'll piss out your electrolytes faster from not retaining water for as long as normal.