L-carnitine requires a pretty decent insulin spike from carbs (80g is the recommendation) in order to carry it from the blood to muscle, otherwise it is just urinated out as waste. So def not compatible w/ Keto.
L-carnitine increases fat oxidation and spares muscle glycogen. While the uptake is insulin dependent, a higher fat diet may mean higher concentrations of acylcarnitine and therefore lower levels of free carnitine.
I take Actel L Carnitine on an empty stomach and L carnitine with meals for the insulin spike. Did note Acet L Carnitine gave me more clarity at the gym. No noticeable improvements with L Carnitine though.