L Carnitine Benefits, Uses, Dosage, Foods, Side Effects Dr. Axe 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 DrT Pharma Levocarnitine Tablets (330 mg) Levocarnitine Oral Solution (1 g 10 mL multiple unit container) Levocarnitine Oral Solution (Sugar Free) (1 g 10 mL multiple unit container) For oral use only. Not for parenteral use. Frontiers Association between fatigue, peripheral serotonin, and L carnitine in hypothyroidism and in chronic fatigue syndrome