L carnitine Injections for Fat Loss: Fact or Myth? Evidence Based Body Recomposition 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 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 Injection Benefits and Safety Things I wish I knew before Starting Injectable L Carnitine. : r Supplements L carnitine or what we call Skinny drip, is an amino acid naturally found in the body, which helps to convert fat into energy. Taking an injection of L carnitine once a week for 12 weeks can help