Alpha lipoic acid benefits: diabetic neuropathy evidence, R-lipoic acid vs standard ALA, dosage and who should avoid it

What alpha lipoic acid is and what it does

Alpha lipoic acid (ALA, also called thioctic acid) is a compound your body makes itself. Inside cells it works as a coenzyme, a helper for the enzymes that produce energy in mitochondria. It’s sometimes called a “universal antioxidant” because it dissolves in both water and fat.

Food contains small amounts, in offal, spinach, broccoli, tomatoes and peas. But in food it’s bound to protein, and eating it hasn’t been found to raise free ALA in the blood noticeably. Supplements can provide up to 1,000 times more than you’d get from food.

People take it:

• for diabetic neuropathy – burning, pain and numbness in the feet;
• to lower blood sugar;
• “for energy”, weight loss or as a general antioxidant.

Good trials exist only for the first of these.

Medicine in some countries, supplement in others

In Germany, ALA is approved as a prescription treatment for diabetic neuropathy. In some other countries, thioctic acid is sold in pharmacies as licensed tablets and infusions. In the UK and the US, it’s sold as a food supplement.

The difference is regulation, not chemistry. A licensed medicine comes with a patient leaflet, and drips are only given in a clinic. If you’ve been prescribed thioctic acid abroad, don’t swap it for a supplement without checking with your doctor.

R-lipoic acid vs standard alpha lipoic acid

ALA comes in two mirror-image forms, R and S. Your body only makes the R-form. Most supplements contain a racemic mix – half R, half S (labelled “alpha lipoic acid” or “R,S”). R-lipoic acid (R-ALA) is sold separately.

The Linus Pauling Institute concludes it’s still unclear which form is better. Standard racemic ALA, the form used in trials, is a sensible choice.

Alpha lipoic acid for diabetic neuropathy

This is the main area where ALA has evidence, and drips and tablets gave different results:

• Drips. Meta-analyses found that 300–600 mg a day by infusion for 2–4 weeks eased neuropathy symptoms to a clinically meaningful degree.
• SYDNEY 2 (2006), 181 patients. 600, 1,200 or 1,800 mg by mouth for 5 weeks. Total symptom scores (stabbing and burning pain, tingling, numbness) fell by 48–52%, against 32% with placebo. 600 mg worked as well as the higher doses, while nausea, vomiting and dizziness rose with dose.
• ALADIN III, over 500 patients. Nerve function, as assessed by doctors, improved after 3 weeks of drips, but after 6 months of 1,800 mg tablets there was no difference from placebo.
• NATHAN 1 (2011), 460 patients, 4 years. 600 mg by mouth didn’t change the main composite outcome, though some secondary measures improved. On placebo, too, the main outcome barely worsened, so the trial couldn’t show whether ALA slows nerve damage. Serious adverse events were more common on ALA (38% vs 28%), although overall tolerability was similar.
• A 2023 meta-analysis of tablets. Symptoms improved, with a larger effect at higher doses. Nerve conduction and pain scale scores didn’t change.

The Linus Pauling Institute notes that many of these trials came from one German research group funded by the manufacturer. Neuropathy is managed first and foremost by controlling blood sugar. ALA is an add-on to discuss with your diabetes team.

Alpha lipoic acid and blood sugar

ALA makes cells more sensitive to insulin. In a trial of 72 people with type 2 diabetes, 600–1,800 mg a day improved insulin sensitivity by 25% within 4 weeks. A 2018 meta-analysis (20 trials, 1,245 people with metabolic disorders) found lower fasting glucose, insulin and HbA1c. Yet in a trial of 102 people, 600 mg for 16 weeks didn’t change fasting glucose.

In practice: with insulin or diabetes tablets, ALA can cause hypos. Only start it with your diabetes team’s agreement, and test your blood sugar more often.

Insulin autoimmune syndrome

This is a rare but important complication. The immune system starts making antibodies against the body’s own insulin. The result is repeated hypos – weakness, sweating, hunger, dizziness – sometimes alternating with high sugar after meals.

• It has been described in people without diabetes who started taking ALA.
• It’s more likely in people with certain HLA gene variants. Most cases come from Japan, with reports from India and Italy.
• MSKCC mentions around 27 reported ALA-related cases.
• Once the supplement is stopped and the condition treated, the outlook is usually good.

If you get episodes of shakiness, sweating and weakness while taking ALA, especially before meals, stop it and see a doctor.

Alpha lipoic acid dosage: how to take it

• Neuropathy trials used 600 mg once a day; you can start with 300 mg.
• Food cuts absorption by about 20–30%, so take it 30 minutes before breakfast or lunch.
• 1,200–1,800 mg gave no extra benefit but caused more nausea, vomiting and dizziness.
• Trials assessed neuropathy symptoms after 3–5 weeks.

ALA is often combined with B vitamins or CoQ10. Start supplements one at a time so you can tell which one is having an effect.

Side effects and who should check first

The most common side effects are skin reactions (rash, hives, itching), stomach pain, nausea, vomiting, diarrhoea and dizziness. At 1,200 mg a day, unpleasant-smelling urine has been reported. Rare severe allergic reactions have followed drips.

Take extra care with:

• Insulin and other diabetes medicines – risk of hypos.
• Levothyroxine. In a 1991 experiment in rats, ALA reduced the conversion of the thyroid hormone T4 to active T3 by 56%. This hasn’t been studied in people, but a TSH check after starting is sensible.
• Chemotherapy and radiotherapy. As an antioxidant, ALA may interfere with treatment. Only with your oncologist’s agreement.
• Pregnancy. One observational study found no harm from 600 mg a day, but the Linus Pauling Institute advises use only under strict medical supervision. Avoid it while breastfeeding.
• Children. Keep it out of reach. A 20-month-old who swallowed four 600 mg tablets was admitted to hospital with seizures and loss of consciousness. A teenager died after a very large dose.

You can check supplement combinations in our vitamin compatibility chart.

How to choose alpha lipoic acid on iHerb

1. Decide why you want it. With neuropathy or diabetes, see your GP first. If you’re unsure what you need, try our vitamin check.
2. Pick the form: standard racemic ALA as the default; R-ALA only if you’ll pay more without a proven advantage.
3. Check the dose: 300 or 600 mg per capsule.
4. Compare the price per 600 mg, not per bottle.
5. Prefer products with independent quality testing (USP, NSF and similar seals).

Our guide to reading a supplement label explains the Supplement Facts panel. Other supplements for metabolism are in our energy and heart section. Another product marketed for “recycling antioxidants” is glutathione.