L-Ornithine
A non-protein amino acid in the urea cycle, primarily used as L-ornithine L-aspartate (LOLA) in liver clinics for hepatic encephalopathy. Outside hepatology, evidence for ergogenic, sleep, and growth-hormone benefits comes from small Japanese RCTs and is preliminary.
Quick decision guide
May help most
Patients with hepatic encephalopathy (under hepatology care), and athletes interested in possible exercise-fatigue and recovery benefits from ammonia buffering.
Common dosing range
Hepatic encephalopathy (LOLA): 9–18 g/day oral or IV in clinical settings; general supplementation: 400–2,000 mg/day; exercise use: 2–6 g/day.
When to expect effects
Days for hepatic encephalopathy; weeks for sleep/stress markers.
Watch out for
High doses (>10 g/day) can cause GI upset; people with kidney disease should avoid amino acid supplements without medical advice.
Evidence snapshot
What is it
L-ornithine is a non-essential, non-protein amino acid that plays a central role in the urea cycle, where it helps the body dispose of nitrogen waste as urea. It is also a precursor to polyamines and is marketed for ammonia detoxification, athletic recovery, and sleep support.
Is it worth it for you?
Use this as a quick fit check, not a diagnosis.
Worth considering if…
Probably skip if…
Evidence at a glance
| Goal | Effect | Best fit | Time |
|---|---|---|---|
Hepatic encephalopathy (as L-ornithine L-aspartate / LOLA) Good Evidence | RR ~1.9 for HE improvement vs placebo; no clear advantage over lactulose or rifaximin | Cirrhotic patients with overt or minimal HE under hepatology care | Days (with overt HE); weeks for minimal HE psychometric improvement |
Exercise fatigue and recovery Limited Evidence | Reduced post-exercise ammonia; small but statistically significant performance and recovery gains in pilot trials | Endurance and intermittent-anaerobic athletes willing to try a low-risk adjunct | Single dose for acute ammonia buffering; 1–2 weeks for cumulative effect |
Sleep quality and stress markers Limited Evidence | Significant reduction in serum cortisol and cortisol/DHEA-S ratio; improved subjective sleep quality at 400 mg/day for 8 weeks | Adults with chronic mild work stress and poor sleep willing to try a low-risk amino acid | 4–8 weeks for cortisol and sleep changes |
Growth hormone secretion Mixed Evidence | No reliable GH effect at oral doses; older IV studies don't translate to oral use | Not applicable for general use | Not established for oral use |
Wound healing and post-surgical recovery Mixed Evidence | Inconsistent results in clinical nutrition settings; no benefit established for routine wound healing | Critically ill or burn patients under clinical nutrition supervision | Not established for routine use |
Hepatic encephalopathy (as L-ornithine L-aspartate / LOLA)
- Effect
- RR ~1.9 for HE improvement vs placebo; no clear advantage over lactulose or rifaximin
- Best fit
- Cirrhotic patients with overt or minimal HE under hepatology care
- Time
- Days (with overt HE); weeks for minimal HE psychometric improvement
Exercise fatigue and recovery
- Effect
- Reduced post-exercise ammonia; small but statistically significant performance and recovery gains in pilot trials
- Best fit
- Endurance and intermittent-anaerobic athletes willing to try a low-risk adjunct
- Time
- Single dose for acute ammonia buffering; 1–2 weeks for cumulative effect
Sleep quality and stress markers
- Effect
- Significant reduction in serum cortisol and cortisol/DHEA-S ratio; improved subjective sleep quality at 400 mg/day for 8 weeks
- Best fit
- Adults with chronic mild work stress and poor sleep willing to try a low-risk amino acid
- Time
- 4–8 weeks for cortisol and sleep changes
Growth hormone secretion
- Effect
- No reliable GH effect at oral doses; older IV studies don't translate to oral use
- Best fit
- Not applicable for general use
- Time
- Not established for oral use
Wound healing and post-surgical recovery
- Effect
- Inconsistent results in clinical nutrition settings; no benefit established for routine wound healing
- Best fit
- Critically ill or burn patients under clinical nutrition supervision
- Time
- Not established for routine use
Evidence for 5 uses
AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.
Hepatic encephalopathy (as L-ornithine L-aspartate / LOLA)
Disease adjunctLOLA is widely used in European liver units as an ammonia-lowering agent for overt and minimal hepatic encephalopathy. A 2018 Cochrane review of 36 RCTs (n=2,377) found a beneficial effect on HE vs placebo in pooled analyses, with the signal weaker in low-risk-of-bias trials and very low overall GRADE certainty. Earlier meta-analyses (Jiang 2009, PMID 18823442) showed RR 1.89 for HE improvement. LOLA does not clearly outperform lactulose or rifaximin (established first-line therapies). Mechanism: ornithine and aspartate are substrates for the urea cycle and glutamine synthetase, reducing serum ammonia.
Bottom line: Reasonable adjunct in HE under specialist care. Not better than lactulose or rifaximin and not for self-supplementation.
Exercise fatigue and recovery
Supplement benefitSugino et al., 2008 (n=17 crossover) showed L-ornithine 2 g/day for 7 days plus 6 g acute dose suppressed the exercise-induced rise in blood ammonia and improved cycle-ergometer performance in women. Demura et al., 2011 (PMID 21431425) found pre-exercise L-ornithine HCl 0.1 g/kg increased mean anaerobic power output and recovery in men. These are small Japanese trials; effect sizes are modest and have not been replicated in large athletic populations.
Bottom line: Possibly useful for serious athletes; the evidence base is small and most trials are from a single Japanese research group.
Sleep quality and stress markers
Supplement benefitMiyake et al., 2014 (PMID 24889392) in 52 Japanese workers with mild fatigue found L-ornithine 400 mg/day for 8 weeks reduced serum cortisol and the cortisol/DHEA-S ratio vs placebo, and improved perceived sleep quality on standardized questionnaires. A separate crossover study showed L-ornithine reduced post-alcohol salivary cortisol and morning fatigue in flushers. Effects are modest and need replication in non-Japanese populations.
Bottom line: Modest, plausible benefit on stress markers and sleep in mildly stressed workers. Not a sleep medication; combine with sleep hygiene.
Growth hormone secretion
Mechanism onlyOlder studies using high-dose IV arginine/ornithine showed transient growth hormone spikes, but oral supplementation at typical doses (1–6 g/day) does not produce clinically meaningful GH increases in healthy adults. This use is largely a marketing claim with weak evidence.
Bottom line: Skip ornithine for GH-boosting purposes — oral supplements don't produce meaningful GH changes.
Wound healing and post-surgical recovery
Mechanism onlyOrnithine alpha-ketoglutarate (OKG) has been studied in critically ill and post-surgical patients as a protein-sparing nutritional support, with mixed results. As a routine wound-healing supplement in healthy adults, evidence is sparse and unconvincing.
Bottom line: Not worth taking for general wound healing.
How it works
How to take it
What to track
Bottom line: Start low (400–2,000 mg/day) and assess at 4–8 weeks. LOLA for hepatic encephalopathy belongs in hepatology care, not self-supplementation.
4 commercial forms
Compare the main delivery options and what they’re best suited for.
L-ornithine HCl
Most commonOrnithine hydrochloride, the standard supplement form sold in capsules and powders. Well absorbed; used in the Sugino, Demura, and Miyake clinical trials.
Standard reference form; well absorbed.
L-ornithine L-aspartate (LOLA / Hepa-Merz)
Clinical HECombines ornithine with aspartate — both substrates for ammonia-handling pathways. The form used in European hepatology for hepatic encephalopathy. Available oral and IV in clinical settings.
Used clinically; not a typical OTC supplement.
L-ornithine alpha-ketoglutarate (OKG)
Clinical nutritionCombines ornithine with alpha-ketoglutarate as a nitrogen-sparing nutritional support. Mostly used in critical care, burns, and post-surgical nutrition under medical supervision.
Used in clinical nutrition; not for general supplementation.
Combo amino acid blends (with arginine, citrulline, etc.)
Sports nutritionPre-workout and 'GH-booster' formulas commonly combine ornithine with arginine, citrulline, glutamine, and BCAAs. Evidence for added benefit over single ingredients is limited; check elemental amino acid doses on the label.
Variable; total ornithine per serving is what matters.
Safety
Know the common side effects, key cautions, and who should avoid it.
Common side effects
Serious risks
High-dose amino acid supplementation increases renal nitrogen load — people with chronic kidney disease or reduced eGFR should avoid without nephrology input.
Doses above 10 g/day commonly cause GI symptoms (cramping, diarrhea); reduce or split dose if symptoms appear.
Safety in pregnancy, breastfeeding, and children has not been adequately studied — avoid in these populations.
Who should avoid it
- People with chronic kidney disease or reduced renal function without medical supervision.
- Pregnant or breastfeeding people — insufficient safety data.
- Children — no clinical data supporting safety or efficacy in pediatric supplementation.
- People with hereditary urea cycle disorders other than under specialist care.
Pregnancy & breastfeeding
Safety in pregnancy and lactation has not been adequately studied. There is no medical reason to supplement L-ornithine during pregnancy. Avoid supplemental use; dietary amino acid intake from normal protein-containing foods is sufficient.
Bottom line: Generally well tolerated at typical doses (400 mg–2 g/day). Avoid in CKD, pregnancy, and children. GI side effects are the main practical concern at higher doses.
Interactions
Ornithine, arginine, and lysine share intestinal amino acid transporters; high doses of one can modestly reduce absorption of the others. Practically minor unless taking very large amounts.
Generally used together in HE management; combination is well-tolerated and may have additive ammonia-lowering effect. Used by hepatology specialists.
Some amino acids can modestly affect insulin secretion; clinically negligible effect at typical ornithine doses.
Cumulative amino acid load could exacerbate GI side effects or nitrogen load in renal impairment; otherwise no specific interaction.
Choosing a product
What to look for on the label — and what to be skeptical of.
Look for…
Be skeptical of…
Frequently asked questions
Is ornithine an essential amino acid?⌄
No. Ornithine is non-essential and is not even used to build proteins. The body produces it from arginine during the urea cycle. However, dietary or supplemental intake can support specific clinical and athletic uses.
Will ornithine help me sleep?⌄
Small studies suggest modest improvements in sleep quality and stress markers at 400 mg before bedtime. Effects are subtle; it is not a substitute for sleep hygiene or evidence-based insomnia treatments.
Does ornithine boost growth hormone?⌄
Older claims are weakly supported. Oral ornithine at typical doses does not produce meaningful growth hormone elevations in trained adults.
Can I take ornithine with arginine?⌄
Yes, the two are often combined. They share absorption transporters, so very high doses of one may affect uptake of the other, but typical combination products work fine.
Is ornithine safe long-term?⌄
Short-term studies show good tolerability at typical doses. Long-term high-dose safety is less well-characterized. For general use, doses of 1-2 g/day appear safe in healthy adults.
References by claim
Hepatic encephalopathy (as L-ornithine L-aspartate / LOLA)
Sleep quality and stress markers
Miyake et al., 2014 — Nutrition Journal (2014) link
Exercise fatigue and recovery
Track L-Ornithine with Pilora
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Coming to App StoreDisclaimer: 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.