I use the Jarrow brand of Acetyl L- Carnitine because I needed it in a lesser strength (250mg) and it was hard to find. The 500mg effected my sleep even though I took it in the AM. (I'm a tiny person and sleep sensitive) I think the regular amount is 500mg but I'm not sure. I use several different supplement companies. I try to get them as clean as possible meaning without lots of fillers, etc., but that's just me.