When sourcing L-Carnitine injections, the purity level should be ≥99% to ensure efficacy and safety. It is critical to verify that the product is manufactured in a GMP-certified (Good Manufacturing Practice) facility. For B2B buyers, the concentration typically ranges from 500mg/5ml to 2g/5ml; ensure the concentration matches your target market's medical or fitness requirements. Additionally, the solution must be sterile, pyrogen-free, and have a pH value stabilized between 6.0 and 6.5 to prevent tissue irritation.