From the Manufacturer:
"Supports Cardiovascular Function L-Carnitine is an amino acid.
Twinlab Mega L-Carnitine Tablets contain no synthetic D-Carnitine or DL-Carnitine. D-Carnitine and DL-Carnitine are less effective than L-Carnitine. D-Carnitine and DL-Carnitine are not recommended because of their adverse physical side effects."