Alpha-lipoic acid (ALA, also called thioctic acid) is a sulfur-containing fatty acid the body makes in small amounts, where it works as a helper molecule for enzymes in the mitochondria. Supplements usually contain the racemic (R and S) form.
Also known as: ALA, thioctic acid, lipoic acid.
Alpha-lipoic acid has no intake value or upper limit. Published pharmacokinetic studies used single doses of 50 to 600 mg by mouth (Breithaupt-Grögler 1999; Teichert 1998; Hermann 2014). These are study protocols, not a recommendation.
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling. For compounding, it sits in FDA's 503A Category 1 (bulk substances under evaluation, list updated May 14, 2026). In parts of Europe, oral racemic ALA is used as a medicine for symptoms of diabetic nerve damage, which is a separate regulatory status from US supplements.
Absorption by mouth is quick but incomplete: one study measured an absolute bioavailability of about 29% (Teichert 1998), limited mostly by the liver clearing it on first pass. Women had 20 to 32% higher exposure than men in one study, which the authors judged did not need a dose change (Hermann 2014).
In healthy volunteers given 50 to 600 mg by mouth (Breithaupt-Grögler 1999), alpha-lipoic acid peaked 30 minutes to 1 hour after a dose and fell with a half-life of about 30 minutes. Another study (Teichert 1998) measured 25 to 33 minutes, and a third reported median peaks at 20 to 30 minutes after 600 mg (Hermann 2014). Dose Track uses 30 minutes for both.
Numbers shown are the values Dose Track uses, listed only where they agree with the source above. Half-life varies from person to person and with injection site.