L-tyrosine: Evidence, Trial Doses & Interactions

About L-tyrosine

A non-essential amino acid and the precursor to dopamine, noradrenaline and adrenaline. It is also the precursor for thyroid hormone and for melanin.

Tyrosine has one of the more precisely specified effects in this catalogue, and the specification is the important part. Reviews of the literature converge on the conclusion that tyrosine improves cognitive performance only under conditions that deplete catecholamines — extreme cold, prolonged sleep loss, high cognitive load, acute stress — and does essentially nothing in rested, unstressed people. Military and cold-exposure studies are where the positive results live. Marketing that presents it as a general nootropic is describing a condition-dependent effect as an unconditional one. N-acetyl-L-tyrosine, sold as a better-absorbed form, actually converts to tyrosine poorly and is largely excreted.

Sold as

Powder, Capsule, N-acetyl-L-tyrosine

Standardised to

Grams of free L-tyrosine; body-weight dosing at 100–150 mg/kg is common in trials — a product without this marker may not resemble what was studied.

Also known as

Tyrosine, N-acetyl-L-tyrosine, NALT

Regulation: Sold as a dietary supplement with no pre-market efficacy review. Not prohibited in sport.

What the research used

The amounts, forms and durations published trials of L-tyrosine actually administered.

These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.

Studied for Cognitive performance under acute stress or sleep loss
100–150 mg/kg
Limited
Single dose 30–60 minutes before the demanding task
Roughly 7–12 g for an adult, which is a large dose. Trials use military-style stressors — cold, noise, sustained operations — and effects in unstressed conditions are absent.

This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.

When it was taken

Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.

Each timing below was actually compared against an alternative in a trial, which is unusual.

On an empty stomach
Limited
Taken away from protein-containing meals because other large neutral amino acids compete for the same blood-brain barrier transporter, which is established transport pharmacology. Trials dose 30–60 minutes before the task to match the plasma peak.
Timing was tested. A trial compared this window against another and reported a difference.

What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.

Alertness and energy

Energy & Metabolism

Limited evidence

Trials in sustained military operations and cold exposure report better maintained alertness and performance with tyrosine. This does not extend to a general stimulant or focus effect in ordinary conditions.

Limited evidence. Early human work, or mostly lab and animal research.

View the 4 sources

Effects of L-Tyrosine Ingestion on Endurance Performance in Mentally Fatigued Cyclists.(opens in a new tab)
Randomised controlled trial · European journal of sport science · 2026 · PMID 41818465
Treatment of narcolepsy with L-tyrosine: double-blind placebo-controlled trial.(opens in a new tab)
Randomised controlled trial · Lancet (London, England) · 1989 · PMID 2572797
Oral L-Tyrosine Supplementation Improves Core Temperature Maintenance in Older Adults.(opens in a new tab)
Randomised controlled trial · Medicine and science in sports and exercise · 2020 · PMID 31609301
Oral l-tyrosine supplementation augments the vasoconstriction response to whole-body cooling in older adults.(opens in a new tab)
Randomised controlled trial · Experimental physiology · 2017 · PMID 28477375

Deep research mode adds each paper’s own conclusion and stated limitations.

Cognitive function

Brain & Cognitive Health

Limited evidence

Reviews conclude that tyrosine improves working memory and cognitive flexibility under demanding conditions such as cold exposure, sleep deprivation and high cognitive load, and produces no measurable benefit in rested people under normal conditions. The effect is real and narrow.

What may be going on: Tyrosine is the rate-limiting precursor for dopamine and noradrenaline synthesis. Under sustained stress, catecholamine turnover outpaces synthesis, and supplying substrate appears to help only in that state.

Limited evidence. Early human work, or mostly lab and animal research.

View the 1 source

Tolebrutinib in Nonrelapsing Secondary Progressive Multiple Sclerosis.(opens in a new tab)
Randomised controlled trial · The New England journal of medicine · 2025 · PMID 40202696

Deep research mode adds each paper’s own conclusion and stated limitations.

Mood

Mental Wellbeing

Not enough evidence

Tyrosine has been trialled for depression on the catecholamine precursor rationale without success. There is not enough evidence to support a mood claim.

Not enough evidence. Not enough human research to say anything useful yet.

View the 4 sources

Baseline-dependent effect of dopamine's precursor L-tyrosine on working memory gating but not updating.(opens in a new tab)
Randomised controlled trial · Cognitive, affective & behavioral neuroscience · 2020 · PMID 32133585
Utilization of tyrosine-containing dipeptides and N-acetyl-tyrosine in hepatic failure.(opens in a new tab)
Randomised controlled trial · Hepatology (Baltimore, Md.) · 1995 · PMID 7705801
Tyrosine for depression: a double-blind trial.(opens in a new tab)
Randomised controlled trial · Journal of affective disorders · 1990 · PMID 2142699
Treatment of narcolepsy with L-tyrosine: double-blind placebo-controlled trial.(opens in a new tab)
Randomised controlled trial · Lancet (London, England) · 1989 · PMID 2572797

Deep research mode adds each paper’s own conclusion and stated limitations.

Things to know

Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.

Interaction
MAO inhibitors
Interacts withMAO inhibitors, including phenelzine and tranylcypromine
Tyrosine is a precursor to catecholamines and to tyramine. Combining large doses with monoamine oxidase inhibitors risks a hypertensive reaction, and the combination should be avoided.
Interaction
Thyroid hormone and thyroid disease
Interacts withLevothyroxine, antithyroid drugs
Tyrosine is a substrate for thyroid hormone synthesis. It is generally avoided in hyperthyroidism and Graves disease, and anyone on thyroid medication should raise it with their prescriber. It also competes with levothyroxine for absorption if taken together.
Worth knowing
Melanoma and pigmented lesions
Tyrosine is the precursor to melanin, and it is conventionally avoided in people with a history of malignant melanoma. The concern is theoretical, drawn from tumour biology rather than from human trials.
Too much
Nausea and headache at trial doses
The 100–150 mg/kg doses used in research are large — often 10 g or more — and commonly cause nausea, headache and heartburn.

L-tyrosine

What l-tyrosine may help with

About L-tyrosine

What the research used

When it was taken

On an empty stomach

The evidence in depth

Alertness and energy

Cognitive function

Mood

Things to know

MAO inhibitors

Thyroid hormone and thyroid disease

Melanoma and pigmented lesions

Nausea and headache at trial doses

What l-tyrosine may help with

About L-tyrosine

What the research used

When it was taken

⏳On an empty stomach

The evidence in depth

Alertness and energy

Cognitive function

Mood

Things to know

MAO inhibitors

Thyroid hormone and thyroid disease

Melanoma and pigmented lesions

Nausea and headache at trial doses

On an empty stomach