Frontiers Dietary supplementation with L carnitine elevates intracellular carnitine levels and affects gene expression of SLC25A20 and COX4I1, as well as non mitochondrial respiration of bovine blood cells during systemic immune challenge 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 Best Time to Take L Carnitine: Morning vs Evening for Better Fat Loss & Performance Know About L Carnitine Injections for Weight Loss