Swanson Propionyl L Carnitine with Glycine, Amino Acid, 60 Vegan Capsules, 2 Pack Walmart.com Carnitine: the claims and why it may not work 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 supplements bioavailability is very less and according to some studies it takes 8 to 12 weeks for for loss results, so if you decide to supplement with oral L carnitine do take it in DRUG DELIVERY Oral Delivery of Peptides by Peptelligence Technology