Ornithine alpha-ketoglutarate

amino-acidsalt

What is it

Ornithine alpha-ketoglutarate (OKG, ornithine oxoglutarate) is a salt formed from two molecules of the non-proteinogenic amino acid L-ornithine and one molecule of alpha-ketoglutarate (a Krebs-cycle intermediate). After ingestion it dissociates into its component parts, which feed converging biochemical pathways: ornithine enters the urea cycle and can be converted to glutamate, polyamines, proline, and arginine, while alpha-ketoglutarate serves as a substrate for the tricarboxylic acid cycle, amino acid transamination, and collagen-related prolyl hydroxylase reactions. Together, these substrates are thought to support anti-catabolic, anabolic, and ammonia-buffering effects, the rationale for OKG's historical use in clinical nutrition for burn injury, surgical recovery, and undernourished elderly patients.

Evidence for 4 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Burn and severe trauma nutrition support

Good Evidence

Enteral OKG at 10-30 g/day, often delivered as part of immunonutrition protocols, has been shown in clinical trials of burn and surgical patients to improve nitrogen balance, accelerate wound healing, and reduce length of stay versus standard nutrition. Evidence base is in specialised inpatient settings rather than ambulatory supplement use.

Malnutrition in elderly patients

Limited Evidence

RCTs of 10 g/day OKG over 2-3 months in convalescent and malnourished elderly subjects show modest improvements in body weight, appetite, and functional measures versus placebo. Sample sizes are limited and effects on hard clinical endpoints such as mortality and disability are not well established.

Hepatic encephalopathy and ammonia metabolism

Limited Evidence

L-ornithine L-aspartate (a different salt) is used clinically for hepatic encephalopathy with reasonable evidence; OKG has been studied in smaller cirrhosis cohorts with modest effects on ammonia and nitrogen balance, but OKG itself is not a standard therapy and should not be substituted for guideline-recommended treatments.

Athletic performance and recovery

Mixed Evidence

Studies of OKG for muscle mass, growth hormone, or exercise performance have produced inconsistent results, with most showing no meaningful effect at the doses typically used in sport contexts (1-12 g/day). The clinical rationale that drives benefit in catabolic illness does not translate cleanly to healthy training adaptation.

Dosage

Clinical doses of OKG used in surgical and burn-injury studies are typically 10-30 g per day, often given enterally in divided doses; doses of 10 g/day for 6-12 weeks have been used in trials of elderly malnourished patients. Athletic-performance studies have used 1-12 g/day with mixed results. OKG is rarely sold as a dietary supplement in the United States at the high doses used clinically; doses above 20 g/day should not be taken outside medical supervision. Most regimens distribute the daily dose across 2-3 servings to reduce gastrointestinal load.

Safety

OKG is generally well tolerated; the most common adverse effects are gastrointestinal - nausea, abdominal cramping, and diarrhoea - particularly at doses above 10 g/day. Theoretical concerns exist in patients with impaired hepatic urea-cycle function or severe renal disease because of the nitrogen load, and OKG should be avoided in inborn errors of urea-cycle metabolism. No clinically significant drug interactions are well established. Safety in pregnancy and lactation has not been adequately studied. The combined intake of ornithine and alpha-ketoglutarate from food sources is small relative to supplemental doses, so high-dose use should be regarded as pharmacological rather than nutritional replenishment.

References

Wikidata: ornithine oxoglurate (Q7103624) — Wikidata link
PubChem CID 78866: Ornithine alpha-ketoglutarate — PubChem link
NIH Dietary Supplement Label Database: Ornithine Alpha-Ketoglutarate — DSLD link

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.