What are potential side effects of alpha-lipoic acid supplements?
Executive summary
Alpha‑lipoic acid (ALA) supplements most often produce mild, short‑lived adverse effects such as gastrointestinal upset, headaches, and skin reactions, but they carry specific risks — notably lowering blood sugar and interacting with certain drugs — and, in extremely rare cases, have been linked to severe toxicity and death; regulatory approval for therapeutic use is lacking and evidence quality varies [1] [2] [3] [4] [5] [6].
1. Common, usually mild effects: digestive upset, metallic taste and headache
The most frequently reported side effects are gastrointestinal — nausea, stomach upset, diarrhea and abdominal pain — along with headaches and a possible metallic taste in the mouth, which are generally transient and resolve as the body adjusts to supplementation [1] [2] [3].
2. A real risk for people with diabetes: hypoglycemia and glucose interactions
ALA can lower blood glucose levels and may amplify the effects of diabetes medications, creating a tangible risk of hypoglycemia characterized by sweating, weakness, confusion or a fast heart rate; users with diabetes are advised to monitor blood sugar closely and consult clinicians before combining ALA with glucose‑lowering drugs [7] [4] [8] [3].
3. Allergic and dermatologic reactions, plus less common neurologic complaints
Rashes, itching, and other allergic skin reactions have been documented across consumer and clinical reports and may require stopping the supplement, while insomnia and other sleep disturbances have been noted in some reviews, demonstrating that ALA’s side‑effect profile extends beyond the gut [2] [3] [9].
4. Rare but serious harms: liver reports, multi‑organ failure and documented fatalities
Although clinical trials and reviews often report minimal or no adverse effects overall, case reports catalog severe toxicity — including multiorgan failure and at least one adult death — indicating that, while extremely rare, life‑threatening reactions to ALA have been observed and should temper claims of universal safety [6] [5].
5. Drug interactions and vulnerable groups: chemotherapy, alcohol, pregnancy and nutrient depletion
ALA’s antioxidant properties raise concerns that it could blunt the action of some cancer therapies, and because it can lower glucose it may interact with hypoglycemic agents; heavy alcohol users are advised to consider thiamine supplementation when taking ALA, pregnant or breastfeeding people are typically counseled to avoid it, and prolonged ALA use can affect biotin status so co‑supplementation is sometimes suggested — all reasons to screen medications and medical conditions first [7] [8] [1] [10] [3].
6. Dose, evidence quality and competing narratives from industry
Most clinical studies use 300–600 mg daily and often find modest benefits with generally mild side effects, yet absorption and responses vary and the supplement industry sometimes promotes very high doses with claims of safety; authoritative sources note that ALA is not FDA‑approved to treat disease and that evidence of efficacy and long‑term safety remains variable, creating a tension between marketing narratives and cautious clinical reviews [2] [11] [6] [3] [12].
7. Practical takeaway: weigh benefit against specific risks and monitor
For most healthy adults ALA appears tolerable at common doses, but people with diabetes, those on chemotherapy or multiple medicines, pregnant or nursing individuals, and anyone reporting unusual symptoms should consult a clinician, monitor blood glucose and stop the supplement if severe allergic or systemic symptoms appear, because the balance of modest potential benefit and uncommon but real severe adverse events requires individualized judgment [4] [8] [5] [3].