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Types of Alpha-Lipoic Acid: Forms & Bioavailability

Evidence:Moderate
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This content is for informational purposes only and does not constitute medical advice. Statements about dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. Individual results may vary — consult your healthcare provider before starting any supplement. Full disclaimer

Forms Comparison

FormBioavailabilityBest For
R-Lipoic Acid (R-ALA)HighOptimal form — the naturally occurring R-enantiomer is more biologically active and better absorbed than racemic ALA
Racemic Alpha-Lipoic Acid (R/S-ALA)ModerateBudget option — 50/50 mix of R and S enantiomers; the S-form may actually antagonize some R-ALA effects
Na-R-ALA (Sodium R-Lipoic Acid)High (stabilized)Stabilized R-ALA — sodium salt prevents polymerization, a common issue with pure R-ALA

R-Lipoic Acid (R-ALA)

Bioavailability: High. Best for: Optimal form — the naturally occurring R-enantiomer is more biologically active and better absorbed than racemic ALA.

Racemic Alpha-Lipoic Acid (R/S-ALA)

Bioavailability: Moderate. Best for: Budget option — 50/50 mix of R and S enantiomers; the S-form may actually antagonize some R-ALA effects.

Na-R-ALA (Sodium R-Lipoic Acid)

Bioavailability: High (stabilized). Best for: Stabilized R-ALA — sodium salt prevents polymerization, a common issue with pure R-ALA.

References

  1. RCTZiegler D, Ametov A, Barinov A, et al. (2006). Oral treatment with alpha-lipoic acid improves symptomatic diabetic polyneuropathy: the SYDNEY 2 trial. Diabetes Care. DOI PubMed
  2. RCTAnsar H, Mazloom Z, Kazemi F, Hejazi N (2011). Effect of alpha-lipoic acid on blood glucose, insulin resistance and glutathione peroxidase of type 2 diabetic patients. Saudi Medical Journal. PubMed
  3. ReviewShay KP, Moreau RF, Smith EJ, Smith AR, Hagen TM (2009). Alpha-lipoic acid as a dietary supplement: molecular mechanisms and therapeutic potential. Biochimica et Biophysica Acta. DOI PubMed
  4. Meta-analysisPires IZ, Gobbo MODS, Sudo RYU, Milbradt TL, et al. (2025). Efficacy of Alpha Lipoic Acid Supplementation in Sperm Parameters: A Systematic Review and Meta-Analysis of Randomized Trials.. International braz j urol : official journal of the Brazilian Society of Urology. DOI PubMed
  5. Luo Y, Zhang J, Guo H (2025). Alpha-lipoic acid on intermediate disease markers in overweight or obese adults: a systematic review and meta-analysis.. BMJ open. DOI PubMed
  6. Sharifi-Zahabi E, Abdollahzad H (2024). Alpha Lipoic Acid Supplementation and Iron Homeostasis: A Comprehensive Systematic Review and Meta-Analysis of Randomized Controlled Clinical Trials.. International journal for vitamin and nutrition research. Internationale Zeitschrift fur Vitamin- und Ernahrungsforschung. Journal international de vitaminologie et de nutrition. DOI PubMed
  7. Prado MB, Adiao KJB (2024). Ranking Alpha Lipoic Acid and Gamma Linolenic Acid in Terms of Efficacy and Safety in the Management of Adults With Diabetic Peripheral Neuropathy: A Systematic Review and Network Meta-analysis.. Canadian journal of diabetes. DOI PubMed
Show 5 more references
  1. Meta-analysisHsieh RY, Huang IC, Chen C, Sung JY (2023). Effects of Oral Alpha-Lipoic Acid Treatment on Diabetic Polyneuropathy: A Meta-Analysis and Systematic Review.. Nutrients. DOI PubMed
  2. Orellana-Donoso M, López-Chaparro M, Barahona-Vásquez M, Santana-Machuca A, et al. (2023). Effectiveness of alpha-lipoic acid in patients with neuropathic pain associated with type I and type II diabetes mellitus: A systematic review and meta-analysis.. Medicine. DOI PubMed
  3. Kishi T, Sakuma K, Miura G, Ito Y, et al. (2023). Alpha Lipoic Acid for Schizophrenia: A Systematic Review and Meta-analysis.. Journal of clinical psychopharmacology. DOI PubMed
  4. Vajdi M, Mahmoudi-Nezhad M, Farhangi MA (2023). An updated systematic review and dose-response meta-analysis of the randomized controlled trials on the effects of alpha-lipoic acid supplementation on inflammatory biomarkers.. International journal for vitamin and nutrition research. Internationale Zeitschrift fur Vitamin- und Ernahrungsforschung. Journal international de vitaminologie et de nutrition. DOI PubMed
  5. Mahmoudinezhad M, Farhangi MA (2023). Alpha-lipoic acid supplementation affects serum lipids in a dose and duration-dependent manner in different health status.. International journal for vitamin and nutrition research. Internationale Zeitschrift fur Vitamin- und Ernahrungsforschung. Journal international de vitaminologie et de nutrition. DOI PubMed