Side effects of alpha lipoic acid are generally rare. According to Dr. Sahelian, low doses of lipoic acid, such as 5 to 20 mg, show no side effects. But higher doses could cause skin rash, nausea or stomach upset, along with nervousness, fatigue and insomnia.
If you're deficient in thiamine (vitamin B1), a condition often associated with alcoholism, you shouldn't take alpha lipoic acid.

If you're currently being treated with any of the following medications, you shouldn't use alpha lipoic acid without first talking to your health-care provider:

Insulin and drugs that lower blood sugar - Alpha lipoic acid can combine with these drugs to further reduce blood sugar levels, resulting in hypoglycemia (low blood sugar). Tell your doctor before taking lipoic acid, and monitor your blood sugar levels closely; your doctor may need to adjust your medication doses.

Thyroid-regulating medications, Levothyroxine- Alpha-lipoic acid may lower levels of thyroid hormone. Blood hormone levels and thyroid function tests should be monitored.