L-Ornithine (as L-Ornithine Hydrochloride)




Supports brain function *

Supports skin health *

Supports a healthy stress response *


L-Ornithine is an amino acid. It is found in the diet and can be produced in the human body, with the combination determining body stores. Meats, nuts, rice, eggs, fish, soybeans and dairy are the best food sources. Ornithine can be taken up by the brain and is found in many other tissues, with its highest concentrations found in connective tissues, such as the skin. L-ornithine is a precursor for the synthesis of L-proline, which is one of the primary amino acids in collagen, the main structural components of connective tissues. It is also involved in the urea cycle, which is important for the removal of excess nitrogen compounds such as ammonia—these can be fatigue-causing metabolites in active tissues, like the brain and muscles—and in the synthesis of polyamines, which are involved in cell growth and tissue healing. L-ornithine is able to influence a number of brain functions, including hypothalamic-pituitary-adrenal (HPA) axis signaling, as well as GABA and glutamate pathways, for example. 


L-Ornithine Hydrochloride is non-GMO, gluten-free, and vegan.


L-ornithine has been used in clinical studies at doses ranging from 200 mg to a few grams. The most common dose, when given alone in recent human studies, has been 400 mg a day. L-ornithine has had a synergy with caffeine at a dose of 200 mg L-ornithine in combination with 100 mg caffeine [1]. Neurohacker believes L-ornithine follows a threshold response (see Neurohacker Dosing Principles) when given to healthy people, which means we expect the majority of functional benefits to occur within the 200-400 mg range. We dose L-ornithine within this range. 


Brain function 

Influences the hypothalamic-pituitary-adrenal (HPA) axis [2,3]

Supports growth hormone signaling [3–5]

Supports healthy behavioral responses to stress [2,6]

Influences the levels of stress hormones [2,3,5,7–9]

Supports sleep [7,10,11]

Influences melatonin signaling [5,12]

Supports brain metabolism, oxygen utilization, and neutralization of ammonia [13–16]

Metabolic precursor for GABA and glutamate neurotransmitter pathways [17–22]

Supports brain protein synthesis [23–26]

Skin health

Supports skin levels of collagen-constituting amino acids [27]

Supports collagen deposition [28]

Supports wound repair functions [28]

Ergogenic actions

Supports maximal anaerobic exercise performance [29]

Supports resistance to physical fatigue [30]


Caffeine in supporting mood and concentration [1]

Caffeine in influencing the levels of stress hormone [1]


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