L-Tyrosine
SupplementThe medical_score (62) is slightly above the community_score (72) — the difference is -10. Clinical studies demonstrate benefit limited to stress situations [s1, s2], while a portion of the community reports strong everyday effects that are not consistently supported by scientific evidence [c1, c2]. Conversely, many users report no effect, which lowers the community score [c1, c3].
Unlock full information
Dosages, side effects, studies and more — free after registration.
Register for freeRating Scales
TL;DR
L-Tyrosine's strongest evidence is narrow but real: it blunts stress-induced cognitive decline by replenishing depleted catecholamine precursors, not by boosting baseline performance in relaxed individuals. Community reports align with this — users under acute stress or sleep deprivation respond well, while daily supplementation frequently leads to tolerance and diminishing returns. Doses above 2–3 g rarely add benefit but increase the risk of sleep disruption and overstimulation. The absolute contraindication with MAO inhibitors is serious — hypertensive crisis is a genuine, not theoretical, risk.
Description
L-Tyrosine is a non-essential amino acid and precursor of the catecholamines dopamine, norepinephrine, and epinephrine; evidence supports attenuation of stress-induced cognitive deficits [s1, s2].
L-Tyrosine is a conditionally essential, proteinogenic amino acid synthesized by the body from the essential amino acid phenylalanine. As the immediate building block of catecholamine biosynthesis, L-tyrosine stands at the beginning of the pathway: Tyrosine → L-DOPA → Dopamine → Norepinephrine → Epinephrine [s3, s4]. Additionally, L-tyrosine serves as a precursor for the thyroid hormones thyroxine (T4) and triiodothyronine (T3), as well as for the skin pigment melanin [s4]. Clinical evidence is focused on use under acute stress and cognitive load. Several controlled studies demonstrated that a single dose of L-tyrosine (100–150 mg/kg BW or 2–7 g) can partially compensate for stress-induced performance decrements in memory, attention, and reaction time [s1, s2, s5]. The effect appears limited to situations in which catecholamine turnover is elevated by stress, sleep deprivation, or extreme cold exposure and endogenous synthesis becomes rate-limiting [s2, s3]. Evidence for everyday use without a specific stressor is weaker. A systematic review in military populations concluded that available data do not support a strong recommendation [s1]. For ADHD and depression, adequately controlled human studies are lacking; mechanistic plausibility exists but does not constitute proof of efficacy [s6, s7]. EFSA rejected health claims for cognitive function and catecholamine synthesis in 2011 due to insufficient evidence [s10]. L-Tyrosine is considered well tolerated; FDA GRAS status has been recognized for doses up to 150 mg/kg BW/day for up to three months [s8]. N-Acetyl-L-Tyrosine (NALT), a form commonly used in supplements, has lower bioavailability than L-tyrosine itself according to current pharmacokinetic investigations [s9].
Legal Status (DE)
In Germany, Austria, and Switzerland, L-tyrosine is marketable as an over-the-counter food supplement (NEM). The BVL issued a general administrative order in 2013 for the distribution of L-tyrosine-containing supplements (BVL 13/01/009). No specific statutory maximum level regulation for L-tyrosine exists in the EU. EFSA rejected health claims under Art. 13(1) Regulation 1924/2006 for L-tyrosine in 2011, as the evidence was deemed insufficient [s10, s11].
Mechanism of Action
L-Tyrosine is taken up into neurons and adrenal medulla cells via the large neutral amino acid transporter (LNAA). There, the enzyme tyrosine hydroxylase (TH) hydroxylates L-tyrosine to L-DOPA; this is the rate-limiting step of catecholamine synthesis [s3, s4]. L-DOPA is subsequently converted to dopamine (DA) by aromatic amino acid decarboxylase, which in turn can be metabolized to norepinephrine (NE) by dopamine-β-hydroxylase and further to epinephrine in the adrenal gland [s4]. Importantly, TH activity is subject to end-product inhibition by DA and NE. Under normal catecholamine levels, additional tyrosine therefore does not result in meaningful increased synthesis [s2, s3]. L-Tyrosine demonstrably increases catecholamine synthesis only when neurons are actively firing and endogenous precursor availability becomes the limiting factor — as occurs under acute physical or mental stress, sleep deprivation, or cold exposure [s2, s3]. This "demand-dependent" mechanism explains why L-tyrosine shows little stimulatory effect at rest, but can buffer cognitive performance decrements under load [s1, s2]. Additionally, L-tyrosine provides iodination substrate for the thyroid gland; whether supplementation meaningfully increases hormone synthesis in healthy individuals is unestablished, but should be considered a risk in hyperthyroidism [s4, s12].
Side Effects
| Side Effect | Frequency | Severity |
|---|---|---|
| Gastrointestinale Beschwerden (Übelkeit, Magenunruhe) Occasionally reported at higher doses in clinical studies; generally dose-dependent [s8]. | gelegentlich | leicht |
| Kopfschmerzen Reported at high doses and with individual sensitivity [s12, s7]. | gelegentlich | leicht |
| Schlafstörungen / Einschlafprobleme Activation of the sympathoadrenal system via increased catecholamine availability can disrupt sleep when taken in the evening [s2, s8]. | gelegentlich | leicht |
| Überstimulation / Euphorie bei hohen Dosen Individual user reports describe unwanted euphoria and sedation at 750 mg; possibly dose-dependent [c2]. | selten | leicht |
| Hypertensive Krise (bei Kombination mit MAO-Hemmern) MAO inhibitors block the breakdown of catecholamines; additional tyrosine intake can lead to dangerous blood pressure elevation [s12, s13]. | selten | schwer |
| Hyperthyreose-Verschlimmerung L-Tyrosine serves as a substrate for thyroid hormones; theoretical risk of overstimulation in pre-existing hyperthyroidism [s4, s12]. | theoretisch | moderat |
Contraindications
Combination can cause severe hypertension (hypertensive crisis) due to uncontrolled catecholamine surge [s12, s13].
L-Tyrosine is a substrate for thyroid hormone synthesis; supplementation may exacerbate hyperthyroidism [s4, s12].
PKU patients require low-tyrosine specialized diets; supplementation is indicated only under strict medical supervision and only in cases of confirmed tyrosine deficiency [s7, s12].
Insufficient safety data available; supplementation not recommended [s12, s13].
L-Tyrosine is a substrate for melanin synthesis; theoretical promotion of melanoma growth cannot be excluded [s4, s12].
Studies
Tier A — High Evidence
Outcome: Cognitive performance under stress, mood, working memory
Effect Size: Positive effects on stress/cognition; inconsistent results without stressor
Outcome: Reactive and proactive response inhibition in older adults
Effect Size: Significant improvement in proactive inhibition under tyrosine vs. placebo
Outcome: Cognitive and physical performance under stress (military populations)
Effect Size: Weak positive recommendation for cognitive stress; all included studies showed positive trend; no effect size calculated
Tier B — Moderate Evidence
Outcome: Regulation of dopamine synthesis by tyrosine hydroxylase
Effect Size: No clinical effect sizes; mechanistically foundational
Outcome: Catecholamine synthesis pathway, feedback inhibition
Effect Size: Qualitative: TH end-product inhibition limits effects under normal catecholamine conditions
Tier C — Low Evidence
Outcome: Bioavailability comparison of L-tyrosine vs. NALT
Effect Size: L-tyrosine demonstrates superior bioavailability compared to NALT
Community Evidence
Top reported benefits
- Improved concentration and focus, especially under stress
- Increased energy and alertness, reduced fatigue
- Mood elevation with short-term use
- Increased motivation and drive
Top reported issues
- No noticeable effect in many users
- Sleep disturbances when taken in the evening or at high doses
- Tolerance development with long-term daily use
- Unwanted euphoria or restlessness at higher doses (≥750 mg)
A considerable proportion of Reddit users (r/Nootropics) report that L-tyrosine produces no measurable effects, particularly outside of stress situations [c1]. German forum users describe loss of efficacy after several weeks of continuous use and recommend cyclic administration [c3, c4]. Discussions regarding very high doses (≥5 g) are present; clinical relevance remains unclear [c1].
Scientific Sources
- Tyrosine for Mitigating Stress and Enhancing Performance in Healthy Adult Humans, a Rapid Evidence Assessment of the Literature
Jongkees BJ, Hommel B, K\u00fchn S, Colzato LS (2015). Military MedicineBPMID:26126245DOI - The effect of tyrosine supplementation on whole-body endurance performance in physically active population: A systematic review and meta-analysis
Multiple authors (2024). Journal of Sports SciencesBDOI - Tyrosine for Mitigating Stress and Enhancing Performance in Healthy Adult Humans, a Rapid Evidence Assessment of the Literature
Pase MP, Scholey AB, Pipingas A, et al. (2015). Military MedicineAPMID:26126245DOI - Scientific Opinion on the substantiation of health claims related to L-tyrosine and contribution to normal synthesis of catecholamines (ID 1928), increased attention (ID 440, 1672, 1930), and contribution to normal muscle function (ID 1929) pursuant to Article 13(1) of Regulation (EC) No 1924/2006
EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) (2011). EFSA JournalADOI - BVL Allgemeinverfügung: Nahrungsergänzungsmittel mit Zusatz von L-Tyrosin (BVL 13/01/009)
Bundesamt für Verbraucherschutz und Lebensmittelsicherheit (BVL) (2013). BVL BundesanzeigerALink - Should You Try an L-Tyrosine Supplement? A Look at Its Benefits and Side Effects
Cleveland Clinic Health Essentials (2023). Cleveland Clinic Health EssentialsCLink - What Not to Take with L-tyrosine: Essential Safety Information
MedX.it editorial team (2023). MedX.itCLink - Administration of supplemental L-tyrosine with phenelzine: a clinical literature review
Hinz M, Stein A, Uncini T (2014). Drug, Healthcare and Patient SafetyCPMID:25114593DOI - Monoamine Oxidase Inhibitors (MAOIs)
Ershad M, Meseeha M (2024). StatPearls [Internet], NCBI BookshelfCLink - Tyramine and new monoamine oxidase inhibitor drugs
Leblhuber F, Walli J, Deisenhammer E, Tilz GP (1989). British Journal of Psychiatry SupplementCPMID:2695125 - Effect of tyrosine on cognitive function and blood pressure under stress
Deijen JB, Orlebeke JF (1994). Brain Research BulletinCPMID:10230711DOI - Tyrosine supplementation mitigates working memory decrements during cold exposure
Mahoney CR, Castellani J, Kramer FM, et al. (2007). Physiology & BehaviorCPMID:17585971DOI - Tyrosine improves cognitive performance and reduces blood pressure in cadets after one week of a combat training course
Deijen JB, Wientjes CJ, Vullinghs HF, et al. (1999). Brain Research BulletinCPMID:10230711DOI - Effect of tyrosine supplementation on clinical and healthy populations under stress or cognitive demands—A review
Steenbergen L, Sellaro R, Hommel B, et al. (2015). Journal of Psychiatric ResearchBPMID:25797188DOI - Tyrosine promotes cognitive flexibility: evidence from proactive vs. reactive control during task switching performance
Steenbergen L, Sellaro R, Hommel B, Colzato LS (2015). NeuropsychologiaCPMID:24433977DOI - Dose-Dependent Effects of Oral Tyrosine Administration on Plasma Tyrosine Levels and Cognition in Aging
van de Rest O, Blom WA, de Graaf C, et al. (2017). NutrientsCPMID:29271929DOI - Tyrosine supplementation is ineffective in facilitating soccer players' physical and cognitive performance during high-intensity intermittent exercise in hot conditions
Donnan KJ, Williams EL, Stanger N (2025). PLOS ONECDOI - Tyrosine Hydroxylase and Regulation of Dopamine Synthesis
Daubner SC, Le T, Wang S (2011). Archives of Biochemistry and BiophysicsBPMID:21036150DOI - Tyrosine Supplementation: Can This Amino Acid Boost Brain Dopamine and Improve Physical and Mental Performance?
Brosnan JT, Brosnan ME (2020). Gatorade Sports Science Exchange (GSSI)BLink - Neuro-Cognitive Effects of Acute Tyrosine Administration on Reactive and Proactive Response Inhibition in Healthy Older Adults
Colzato LS, Jongkees BJ, Sellaro R, et al. (2018). eNeuro / Frontiers (PMC)APMID:30159395DOI - ADHD and L-Tyrosine: The Dopamine-Precursor Supplement – Clinical Evidence Review
Medical News Today editorial team (2022). Medical News TodayCLink - L-Tyrosine benefits, dosage, and side effects
Examine.com editorial team (2024). Examine.comDLink - Tyrosine: Benefits, Side Effects and Dosage
Healthline editorial team (2023). HealthlineCLink - N-Acetyl-L-Tyrosine vs. L-Tyrosine: A Comparative Analysis of Bioavailability in Humans
BenchChem Research Team (2023). BenchChem Research ReportsCLink
Community Sources
Storage
Unopened
Store cool, dry, and protected from light at room temperature (15–25 °C).
Opened
Keep container tightly closed; avoid moisture and direct sunlight.
Notes
L-Tyrosine as a free amino acid is stable when stored properly. Powder form is hygroscopic; check quality if clumping occurs.