L-carnitine helps the body use fat for energy. It’s mainly used to treat confirmed carnitine deficiency and dialysis-related deficiency. It may also help with heart problems (like angina or heart failure), sperm count and motility in male infertility, and can be given for valproic acid toxicity. Some studies show small benefits for cholesterol, blood sugar in type 2 diabetes, and exercise recovery, but results are mixed. Typical doses up to about 2 g/day are generally safe, with possible side effects like nausea, diarrhea, or a fishy odor. It can raise TMAO levels, which may increase heart risk, so ask a doctor before long-term use, especially if you have heart, kidney, or metabolic issues.