Revisiting the Role of Carnitine in Heart Disease Through the Lens of the Gut Microbiota Injectable L carnitine works better than oral because it goes straight into your bloodstream, giving almost 100% of absorption versus only 518% with capsules or liquid. Oral L carnitine can take upto 4 NuEthix L Carnitine & L Citrulline Supplement Boosts Fat Metabolism L carnitine modified nanoparticles target the OCTN2 transporter to improve the oral absorption of jujuboside B ScienceDirect PDF) Enhanced Bioavailability of L Carnitine After Painless Intradermal Delivery vs. Oral Administration in Rats