Injectable L carnitine vs oral? For me, absorption, fewer GI issues, & energy performance gains make injections the winner. #LCarnitine #Injectable #Bioavailability #MetabolicHealth #EnergyBoost Injectable carnitine vs oral version comparison? L Carnitine injection is recommended at 1 ampule every 2 3 days for best results. The L Carnitine is taken intravenously either by normal injection or using a butterfly needle. After taking this L Carnitine, you L Carnitine Oral Bioavailability NOW l Carnitine Supplement L Carnitine injection is recommended at 1 ampule every 2 3 days for best results. The L Carnitine is taken intravenously either by normal injection or using a butterfly needle. After taking this L Carnitine, you L Carnitine is often marketed as a fat burner, but most people dont realize that oral and injectable L Carnitine are not the same..Oral L Carnitine has poor absorption (only 20% bioavailability),