L Carnitine Injections for Weight Loss Prescription Weight Loss, Inc. ORAL VS. INJECTABLE L CARNITINE , Does it really matter which you use? , Both have pros and cons but it really comes down to what is going to be most suited to use as an individual athlete., L Carnitine Linus Pauling Institute Oregon State University 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