Alpha-lipoic acid is a natural substance made within the body. Yeast, liver, kidney, spinach, broccoli, and potatoes are good sources of alpha-lipoic acid. It is also made in the laboratory for use as a medicine. Alpha-lipoic acid is commonly used to treat nerve pain in people with diabetes (diabetic neuropathy). Pain may be described as burning, tingling, numbness, throbbing, or stabbing.