Supplement analysis backed by scientific evidence · PT

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Moderate evidenceLongevity & antioxidants

R-Alpha Lipoic Acid

The naturally occurring isomer of lipoic acid. Lipoic acid genuinely helps symptoms of diabetic neuropathy, but almost all of that evidence used the cheaper racemic mixture, not the R form specifically.

Evidence last reviewed: August 2026

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What the science says

  • Diabetic polyneuropathy symptoms Moderate evidence

    A meta-analysis and systematic review of randomized trials found oral alpha-lipoic acid improved neuropathic symptom scores in diabetic polyneuropathy compared with placebo. Effects on objective nerve conduction were smaller and less consistent, and the trials mostly used racemic lipoic acid at 600 mg/day.

  • Advantage of the R isomer Limited evidence

    A pilot human pharmacokinetic study found R-lipoic acid reaches higher plasma concentrations than the racemic mixture, with bioavailability varying by age and sex. No clinical trial has compared the R form against racemic lipoic acid on symptoms or any health outcome, so the practical advantage is unproven.

Dosage & safety

Studied doseRacemic trials used 600 mg/day, typically on an empty stomach. R-lipoic acid products are usually dosed at 100–300 mg/day on the assumption of higher potency; stabilized sodium R-lipoate is more stable than free R-lipoic acid.
SafetyCommon effects are nausea, heartburn and rash. Lipoic acid can lower blood glucose, so people on insulin or sulfonylureas need monitoring, and it may worsen thiamine deficiency in heavy drinkers. Insulin autoimmune syndrome (a hypoglycaemia disorder) has been reported, mainly in people of Japanese and Korean ancestry carrying certain HLA types. Avoid in pregnancy and breastfeeding.

Scientific references

Where to buy

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