I think that would vary from person to person.

What carnitine does along with lipoic acid and CoQ-10 is switch the energy production in mitochondria from primarily glucose to fatty acids.

This helps return energy to the cells, and improves functions.

Body builders use very high doses because they have large muscle mass to support.

Regular people, can get by with less I think.

I use 250mg a day normally. When I was working out more at the gym I used 500mg to a gram a day to avoid sore muscles after.

Carnitine can help reduce production of lactic acid, which tends to cause pain and burning. It has been used in the HIV community for many years to help offset the damage from the anti-retroviral drug treatments. It has also shown effectiveness in preventing and improving damage to cells by Chemotherapy drugs for cancer.

I think the dose would depend on the person, their weight, and activity level. Levels higher than 2 grams a day are not necessary for most people. Those on HIV drugs or chemo may use more than that.