Is L Carnitine safe for athletes at doses up to 6000 mg day? Consensus Early research into L carnitine was often cited as underwhelming, showing negligible changes in muscle carnitine content and fat loss outcomes. However, these findings may have been limited by a short study window L Carnitine 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 IV Carnitine Therapy Energy Boost & Metabolism Support Minnerva Clinic L Carnitine For Weight Loss: Diet And Workouts To Follow