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 Injections for Weight Loss Prescription Weight Loss, Inc. Injectable VS Liquid L Carnitine. Which is better? L Carnitine Injections Nuceria Health, Miami, FL L Carnitine: Intravenous vs. Ingested BodyRejuvenation What is L Carnitine, L Carnitine is an amino acid that plays a role in energy production and fat metabolism. Its found in foods like red meat, fish, and dairy, and also available as a supplement.,