I take 1200 mg daily (600 mg morning and evening). One of the side effects some people have with higher dosages is nausea so it might help to start with a lower amount if you have nausea when you try it. Here's some information on the topic:

"How much alpha-lipoic acid should you take?
Because alpha-lipoic acid is an unproven treatment, there is no established dose. However, studies have used between 600-1,800 milligrams daily for diabetes and neuropathy; one review concluded that the evidence is convincing for the use of 600 milligrams daily for three weeks on symptoms of diabetic neuropathy. Some studies have used intravenous alpha-lipoic acid instead of oral supplements."
-- Alpha-Lipoic Acid Supplements: https://www.webmd.com/diabetes/supplement-guide-alpha-lipoic-acid