L-Tyrosine
L-tyrosine is a non-essential, conditionally essential amino acid used to make dopamine and norepinephrine. See what reviews say about stress, thinking, endurance and PKU, and safety gaps.
Content last updated . This page has not been medically reviewed.
What is Tyrosine good for?
What the body uses it for, and how strong the evidence is. A normal job in the body is not proof that extra supplements add benefit; each card says which.
Building block of proteins
Established roleTyrosine is one of the amino acids that join together to make proteins.
Supplements: The body normally makes enough tyrosine; this normal role is not proof that extra supplements help.
Starting material for dopamine, norepinephrine and epinephrine
Established roleThe body uses tyrosine as the first step in making dopamine, norepinephrine and epinephrine, chemical messengers used by the brain and nervous system.
Supplements: The body normally makes enough tyrosine; this normal role is not proof that extra supplements help. Reviews suggest extra tyrosine may matter only when these messengers are temporarily run down.
Thinking under short-term stress or heavy mental demand
Preliminary or mixedA 2015 review concluded tyrosine may improve thinking in short-term stressful or mentally demanding situations, but only when dopamine or norepinephrine is temporarily depleted.
Supplements: Small, short studies; a stricter 2015 assessment made only a weak recommendation and said evidence was too limited for confident advice. Findings for one form do not carry over to others.
Physical endurance
Preliminary or mixedA 2023 meta-analysis of 10 interventions from 8 studies found no difference from placebo in time to exhaustion or time-trial performance in physically active people.
Supplements: No benefit shown for endurance in the reviewed studies (moderate-quality evidence).
Mood, everyday stress and anxiety
Not enough evidenceTyrosine is often sold for stress and mood, but the reviews we read found no solid evidence for these uses; the 2015 review said its potential for clinical disorders seems limited.
Supplements: Not shown to help mood or anxiety in the sources read.
Phenylketonuria (PKU) diets
Not enough evidenceIn PKU, a shortage of tyrosine has been suggested as a cause of some thinking and behaviour problems. A Cochrane review of 3 trials (56 people) found supplements raised blood tyrosine but changed no other outcome.
Supplements: Cochrane could not recommend routine use. Anyone with PKU should follow their individualized diet plan with their health care professional.
Movement control through dopamine
Established roleInherited tyrosine hydroxylase deficiency lowers dopamine, norepinephrine and epinephrine and mainly affects movement.
Supplements: Tyrosine supplements are not described as a treatment for this enzyme condition in the sources read.
Connected topics
Open a group to see how each topic connects and how strong the evidence is.
Health goals (1)
- Cognitive PerformancePreliminary or mixed
Some trials suggest a short-term benefit to thinking under stress or heavy demand, but evidence is limited and may not apply to everyday life.
Body systems (2)
- Nervous SystemEstablished role
The body uses tyrosine to make dopamine, norepinephrine and epinephrine, which the nervous system relies on. This normal role is not proof that extra supplements help.
- Brain & FocusPreliminary or mixed
Reviews suggest tyrosine may help thinking in short-term stressful or demanding situations; evidence is limited and is not shown for everyday focus.
Body parts (2)
- BrainEstablished role
Brain cells use tyrosine as the starting material for dopamine and norepinephrine. Normal intake already covers this role.
- Nervous SystemEstablished role
Tyrosine feeds the pathway that makes the chemical messengers used by the nervous system.
Functional actions (2)
- Nervous System SupportEstablished role
Tyrosine is the raw material for dopamine, norepinephrine and epinephrine. The body makes enough in most people, so extra is not shown to add benefit.
- Cognitive EnhancementPreliminary or mixed
A 2015 review found tyrosine may improve thinking only in short-term stress or high mental demand; a stricter assessment gave a weak recommendation and called evidence insufficient.
Urgent point first: PKU
Phenylketonuria (PKU) is an inherited condition in which phenylalanine builds up. It is managed with an individualized diet worked out with a health care professional. [1] People with PKU should not add tyrosine on their own; a Cochrane review found no basis to recommend it for routine care. [2]Quick answer
Tyrosine is an amino acid the body can make, so it is not essential. MedlinePlus lists it as nonessential and also as conditionally essential, meaning it may be needed from outside in illness and stress. [3] It is the starting material (precursor) for the brain chemicals dopamine and norepinephrine, which is why it is marketed for focus and stress. [4] Do not confuse L-tyrosine with N-acetyl-tyrosine or with blends sold for focus; results for one form cannot be applied to another. See what nootropics are and nootropic safety and claim checks.Evidence by use
Labels: promising but limited, no benefit shown in healthy adults, and insufficient evidence.| Question | What the sources found | Label |
|---|---|---|
| Thinking under short-term stress or demanding tasks | A 2015 review concluded tyrosine can enhance cognitive performance, particularly in short-term stressful or demanding situations, but only when dopamine or norepinephrine is temporarily depleted. [4] | Promising but limited |
| Same question, stricter review | A rapid evidence assessment of 10 randomized and 4 controlled trials made a weak recommendation in favor of tyrosine for cognitive stress, but said the evidence was insufficient for confident recommendations. [5] | Promising but limited |
| Physical performance and endurance | The same assessment made no recommendation for physical performance. [5] A 2023 meta-analysis of 10 interventions from 8 studies found no difference from placebo for time to exhaustion or time-trial performance (moderate-quality evidence). [6] | No benefit shown in healthy adults |
| Clinical disorders | The 2015 review said the potential of tyrosine to treat clinical disorders seems limited. [4] | Insufficient evidence |
| PKU | Blood tyrosine rose with supplements, but no other outcome differed in the 3 trials (56 people) included; the review said no recommendation could be made. [2] | Insufficient evidence |
| Everyday stress relief, mood, weight loss | Proper evidence not found in the reviews we read. | Insufficient evidence |
Both cognition reviews are from 2015, so newer trials may exist that these sources do not cover.
Amounts and official limits
Amounts in studies are study amounts, not advice, and the reviews above do not set a safe amount. No official recommended intake or upper limit for tyrosine was found. A 2023 review noted that no national health agency has set upper limits for individual amino acids, and tyrosine was not among the ten amino acids it proposed values for. [7]Frequently asked questions
Is tyrosine an essential amino acid?
No. MedlinePlus lists it as nonessential and conditionally essential. [3]
Does tyrosine improve focus?
Reviews found a possible benefit for short-term stressful or demanding tasks, but the evidence is limited. [4][5]
Does tyrosine help exercise endurance?
A meta-analysis found no difference from placebo for time to exhaustion or time-trial performance. [6]
Does tyrosine treat PKU?
A Cochrane review found that no recommendation could be made for routine use. [2]
Is there an upper limit for tyrosine?
No national health agency has set upper limits for individual amino acids, and none was found for tyrosine. [7]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety and who should ask first
- PKU: see the point at the top.
- Medicines. Interactions with antidepressants, Parkinson's disease medicines or thyroid medicine are not described in the sources we read. Because tyrosine feeds brain chemical pathways, ask a pharmacist before using it if you take any prescription that affects brain chemicals or the thyroid. See how interactions work.
- Pregnancy, breastfeeding, children, older adults, kidney or liver disease, and surgery. Not described in the sources we read. See pregnancy and breastfeeding and supplements before surgery.
- Added stimulants. Focus blends may add caffeine; see reading supplement labels.
Stress or low mood that is hard to manage deserves proper support: stress safety and when to get help and supplements, teas and adaptogens for stress compared. See also L-theanine.
References
- MedlinePlus Genetics. Phenylketonuria. National Library of Medicine, US. Read 2026-10-22.
- Remmington T, Smith S. Tyrosine supplementation for phenylketonuria. Cochrane Database Syst Rev 2021. Read 2026-10-22.
- MedlinePlus. Amino acids. National Library of Medicine, US (reviewed 1/21/2025). Read 2026-10-22.
- Jongkees BJ et al. Effect of tyrosine supplementation on clinical and healthy populations under stress or cognitive demands: a review. J Psychiatr Res 2015. Read 2026-10-22.
- Attipoe S et al. Tyrosine for mitigating stress and enhancing performance in healthy adult humans: a rapid evidence assessment. Mil Med 2015. Read 2026-10-22.
- Solon-Junior LJF et al. The effect of tyrosine supplementation on whole-body endurance performance in physically active population. J Sports Sci 2023. Read 2026-10-22.
- Elango R. Tolerable upper intake level for individual amino acids in humans: a narrative review of recent clinical studies. Adv Nutr 2023. Read 2026-10-22.