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Amino Acid

L-Ornithine Hydrochloride

Also known as: L-Ornithine HCl, Ornithine HCl, L-Ornithine, Ornithine

C
Evidence

L-Ornithine is a non-essential amino acid involved in the urea cycle and polyamine synthesis, with some evidence suggesting potential benefits for athletic performance and muscle recovery. Research on ornithine supplementation is limited and mixed, with most studies examining small populations.

Primary uses

  • Athletic performance and endurance
  • Muscle recovery support
  • Growth hormone support
  • Immune function

How it works

  • Substrate for urea cycle and nitrogen metabolism
  • Precursor for polyamine synthesis
  • Potential stimulator of growth hormone release
  • Support for creatine and arginine metabolism

Dosage

Typical range
2–5 grams daily
Timing
Between meals or pre-workout/post-workout
With food
Can be taken with or without food; may be better tolerated with light food if GI sensitivity occurs
Duration
Typically studied in 4–8 week protocols; longer-term safety data limited
Special populations
Pregnant/nursing women should consult a healthcare provider; individuals with kidney disease or on dialysis should avoid without medical supervision due to nitrogen metabolism

Forms

  • Powder· 70/100
  • Capsule· 70/100
  • Hydrochloride salt· 70/100

Safety

Common side effects

  • Gastrointestinal discomfort (nausea, diarrhea at higher doses)
  • Headache (reported in some studies)
  • Abdominal cramping

Contraindications

  • Severe renal impairment or end-stage kidney disease
  • Cirrhosis or advanced liver disease
  • Arginine-restricted diets (ornithine can compete with arginine metabolism)

Evidence notes

Limited clinical research with mostly small trials. Some studies suggest benefits for ammonia clearance and endurance performance, but evidence is preliminary and inconsistent. Not established as a primary performance supplement.

Grade C: Mostly observational or small trials; mechanism is plausible but unproven at scale.

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Medical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider.