L-Tyrosine: Benefits, Dosage, Side Effects And Research

L-tyrosine is an amino acid your body uses to build dopamine, norepinephrine and adrenaline. The best human evidence shows that a single large dose of L-tyrosine can help working memory and mental flexibility hold up during acute stress, such as cold exposure, sleep loss or heavy multitasking.^[2][3] It is not a general “focus booster”: in rested, unstressed people the effects are small or absent, and there is little evidence for long-term daily use.

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What Is L-Tyrosine And How Does It Work?

Tyrosine is one of the 20 amino acids that make up proteins. It is called “conditionally non-essential” because your body can make it from phenylalanine, another amino acid. That conversion depends on an enzyme called phenylalanine hydroxylase, and in people with normal enzyme activity, phenylalanine and tyrosine together cover the body’s needs.^[14] You also get tyrosine from protein-rich foods such as dairy, meat, fish, eggs, soy and legumes.

In the brain, tyrosine is converted into L-DOPA by the enzyme tyrosine hydroxylase. L-DOPA then becomes dopamine, which can be converted into norepinephrine and epinephrine (adrenaline). Unusually for a neurotransmitter pathway, the rate of catecholamine production in the brain responds to how much tyrosine is around. Raising brain tyrosine increases catecholamine output, but mainly in neurons that are actively firing.^[1]

That detail explains most of the research: stress, cold, sleep loss and demanding mental work drive catecholamine neurons hard, and extra tyrosine may help them keep up. A 2015 review summed it up: tyrosine looks like an effective cognitive enhancer “only when neurotransmitter function is intact and DA and/or NE is temporarily depleted.”^[2]

Tyrosine also matters outside the brain. Thyroid hormones are built from tyrosine units on a protein called thyroglobulin, which the thyroid gland iodinates to make thyroxine (T4).^[10] This is why people with thyroid conditions should talk to their doctor before supplementing (see the safety section below).

L-Tyrosine Benefits: What The Research Shows

Evidence ratings: “Moderate” means several small controlled human trials agree; “Limited” means one or two trials or mixed results; “Weak” means little or no supporting human evidence.

Working Memory Under Cold Stress (Evidence: Moderate)

In a U.S. Army study, 19 volunteers sat in cold water (about 10 °C, or 50 °F) for two 90-minute sessions. Each time, they ate a food bar containing either placebo or 150 mg/kg of tyrosine, for a total of 300 mg/kg. The cold made working memory and reaction time worse. With tyrosine, participants got more answers right on a working-memory task and processed information faster than they did on placebo in the cold.^[4] The study used a strong crossover design, but the sample was small and the dose was very large.

Performance During Sleep Deprivation (Evidence: Limited)

A Navy study kept participants awake overnight, so they had been up for more than 24 hours by the end. Half received 150 mg/kg of tyrosine in a split dose and half received a cornstarch placebo. Tyrosine reduced the usual drop in psychomotor performance and cut lapses on a vigilance task. The benefit lasted about 3 hours.^[5] This is one trial, and the authors called for more testing of doses and timing.

Multitasking And Cognitive Load (Evidence: Limited To Moderate)

Twenty adults took 150 mg/kg of L-tyrosine or placebo one hour before a demanding multitasking battery. Tyrosine improved accuracy on the working-memory part of the multitask test. It did not improve arithmetic, visual or auditory monitoring, and it changed nothing on a simple, single-task battery.^[6] That pattern fits the “only under strain” model. In a separate double-blind trial with 22 healthy adults, tyrosine reduced “switch costs” when people had to shift between tasks, a standard measure of cognitive flexibility.^[7]

General Focus In Rested, Unstressed People (Evidence: Weak)

A systematic review of 15 studies found that tyrosine buffered drops in working memory and information processing caused by demanding conditions. The authors also noted that almost every study tested a single dose in a small group.^[3] Nothing here shows that daily tyrosine makes a well-rested person sharper.

Mood, Anxiety, Exercise And Clinical Conditions (Evidence: Weak)

Most studies found no meaningful effect on exercise performance.^[3] Reviewers also judged tyrosine’s potential for treating clinical disorders to be limited. Any benefit likely depends on whether the person’s neurotransmitter function is actually impaired, and how much.^[2] We found no good controlled trials showing that tyrosine reduces anxiety. If you are dealing with anxiety or depression, tyrosine is not a substitute for medical care.

Is L-Tyrosine Useful For ADHD, And Can You Take It With Adderall?

The idea is easy to understand: ADHD medications act on dopamine and norepinephrine, and tyrosine is their precursor. The clinical evidence is thin, though. In an 8-week open trial of L-tyrosine in 12 adults with ADHD, 8 improved within 2 weeks, but all 8 developed tolerance by week 6. The authors concluded that L-tyrosine is not useful for adult ADHD.^[9] There was no placebo group, so even the early response is uncertain.

We found no controlled studies of L-tyrosine combined with Adderall or other stimulants. Because both act on the same neurotransmitter system, ask your prescriber before combining them. For a broader look at the evidence, see our guide to the best nootropics for ADHD.

L-Tyrosine Dosage: What Doses Were Studied?

Most positive trials dosed tyrosine by body weight and took it about an hour before a stressful task. The table below lists the verified studies cited on this page.

Purpose	Dose	Duration	Study
Working memory in the cold	150 mg/kg before each of two cold immersions (300 mg/kg total)	Single test day	Mahoney et al., 2007[4]
Performance during sleep loss	150 mg/kg, split dose	One night	Neri et al., 1995[5]
Multitasking working memory	150 mg/kg, 1 hour before testing	Single dose	Thomas et al., 1999[6]
Dose-response in older vs. younger adults	100, 150 or 200 mg/kg	Single dose	van de Rest et al., 2017[8]
Adult ADHD (open trial)	Not specified in abstract	8 weeks	Reimherr et al., 1987[9]

For perspective, 150 mg/kg is about 10 grams for a 150-pound (68 kg) adult. That is far more than the 500–2,000 mg found in typical capsules.

Higher doses are not automatically better. In a crossover trial, 17 adults aged 60–75 took 100, 150 or 200 mg/kg of tyrosine. Their plasma tyrosine rose with dose and climbed higher than in young adults given the same dose. Working memory got worse as the dose went up, especially in people with the largest plasma response.^[8] Older adults in particular should not assume that more tyrosine means more benefit.

When To Take L-Tyrosine

The trials gave tyrosine about 60 minutes before a stressful or demanding task. In the sleep-deprivation study, the benefit lasted about 3 hours.^[5][6] No trial has directly compared taking it with or without food. Protein-rich meals themselves raise brain tyrosine,^[1] so a large protein meal and a tyrosine supplement are, to some degree, doing similar things. Because tyrosine feeds stimulating neurotransmitters, most people take it in the morning or before a specific demanding event, not at night.

Tyrosine Supplement Forms And What To Look For

• L-tyrosine (free form): The form used in almost every cognitive trial cited above. It is inexpensive and does not dissolve well in water, so powders can be gritty.
• N-acetyl L-tyrosine (NALT): Tyrosine with an acetyl group attached. It dissolves much better in water, which is why it was developed for IV nutrition. Human IV studies found that a large share of NALT leaves the body unchanged in the urine and that it raises blood tyrosine poorly.^[13][14] In a mouse study comparing oral tyrosine “prodrugs,” NALT was the least effective at raising brain tyrosine.^[15] We cover this in detail in NALT vs L-tyrosine.
• Dose per serving: Check how many capsules you would need to reach the amount you want. Studied doses are in the grams, not milligrams.
• Testing: Look for brands that publish third-party certificates of analysis for purity and heavy metals.

L-Tyrosine Side Effects And Safety

In the trials summarized here, single doses of 100–150 mg/kg were generally well tolerated. The sleep-deprivation researchers described tyrosine as “relatively benign” at 150 mg/kg.^[5] The evidence base is mostly single-dose studies in small groups, though, so long-term safety at high doses is not well documented.^[3] The cognitive trials were not designed to catalog side effects in detail, so if you notice stomach upset, headache, jitteriness or trouble sleeping, lower the dose or stop.

The clearest dose-related warning comes from the older-adult trial, where working memory got worse at higher doses.^[8]

Drug Interactions And Who Should Avoid L-Tyrosine

• MAO inhibitors (MAOIs): MAOIs such as phenelzine, tranylcypromine and selegiline block the breakdown of catecholamines. Tyrosine increases catecholamine production in active neurons,^[1] so stacking the two could in theory push catecholamine levels too high and raise blood pressure. We found no controlled studies testing this combination, so the caution rests on mechanism. It is still a serious enough concern to avoid tyrosine if you take an MAOI.
• Thyroid hormone medication or thyroid disease: The thyroid uses tyrosine to build thyroid hormone.^[10] There are no good human trials showing that tyrosine supplements change thyroid levels. If you have hyperthyroidism or Graves’ disease, or take levothyroxine, ask your doctor before using it.
• Levodopa and stimulant medications: These act on the same catecholamine pathway. Ask your prescriber first.
• Phenylketonuria (PKU) and other inherited amino acid disorders: Use tyrosine only under the supervision of the clinician who manages your condition.
• Pregnancy and breastfeeding: Safety data for supplemental doses are lacking. Avoid unless your clinician advises otherwise.
• Older adults: Start low, given the dose-related decline in working memory seen in the van de Rest trial.^[8]

How L-Tyrosine Stacks With Other Nootropics

L-Tyrosine And L-Theanine Together

This is a popular pairing, and the logic is reasonable. Tyrosine supports the stress-depleted catecholamine system, while L-theanine is studied for calm, stress-related symptoms and sleep quality. In a 4-week randomized crossover trial, 200 mg/day of L-theanine reduced stress-related symptom scores and improved some measures of verbal fluency and executive function.^[12] That trial’s theanine and placebo were supplied by a theanine manufacturer.

No trial has tested L-tyrosine and L-theanine together, so any combined benefit is an assumption. The two have no known harmful interaction. Theanine is also often paired with caffeine, which is covered in our L-theanine and caffeine guide.

Taking 5-HTP With Tyrosine

5-HTP is the immediate precursor to serotonin, just as tyrosine (through L-DOPA) is the precursor to dopamine. Some online protocols recommend pairing them, claiming that 5-HTP alone “depletes dopamine.” Be skeptical. The most-cited paper making that argument, Hinz et al. 2012, was retracted by its journal in 2021, so we do not rely on it. No controlled trials support the combination.

The bigger concern is safety. A review of 5-HTP highlights serotonin syndrome as a key risk, especially with other serotonergic drugs such as SSRIs, SNRIs, triptans and tramadol.^[11] If you take any of these, do not add 5-HTP without your doctor’s approval, with or without tyrosine.

Other Pairings

Tyrosine shows up in stress-focused stacks alongside rhodiola rosea and in focus stacks with citicoline. These combinations have not been tested as stacks in trials. See our nootropic stacks guide for a framework for combining ingredients cautiously.

Where To Buy L-Tyrosine

If you want to try a study-style dose for a specific demanding situation, a single-ingredient L-tyrosine powder or capsule is the most practical and affordable option. We recommend Nootropics Depot for single-ingredient products because of its third-party testing. For now, we link to its authorized Amazon store. Buy only from listings that say “Sold by Nootropics Depot.”

Check Nootropics Depot L-Tyrosine on Amazon

If you specifically want NALT, for example for a drink mix where solubility matters, Nootropics Depot also sells it. Read our NALT comparison first: Nootropics Depot N-Acetyl L-Tyrosine.

L-Tyrosine FAQs

What Is L-Tyrosine Used For?

As a supplement, L-tyrosine is mostly used to support mental performance during short periods of stress, such as cold, sleep loss or heavy multitasking. Those are the situations where human studies have found benefits.^[2][3] Medically, related tyrosine compounds are used in IV nutrition.

Does L-Tyrosine Increase Dopamine?

Tyrosine is the precursor to dopamine, and higher brain tyrosine increases catecholamine production in neurons that are actively firing.^[1] It does not act like a stimulant drug, and in resting conditions the effect on behavior appears small.

How Much L-Tyrosine Should I Take?

Positive studies mostly used 100–150 mg/kg as a single dose about an hour before a demanding task.^[4][5][6] Many people use much smaller doses (500–2,000 mg) that have not been well studied. Talk to your doctor before taking gram-level doses, especially if you are older or take medication.

Is It Safe To Take L-Tyrosine Every Day?

Almost all trials tested single doses, so daily long-term use is not well studied.^[3] The one long-term ADHD trial found that benefits faded within weeks.^[9]

Can I Take L-Tyrosine With L-Theanine?

There is no known harmful interaction, and some people like the combination. It has not been tested as a pair, so any extra benefit is unproven.^[12]

Is NALT Better Than L-Tyrosine?

Probably not for raising tyrosine levels. Human IV studies show much of NALT is excreted unchanged, and it raises blood tyrosine poorly.^[13][14] See NALT vs L-tyrosine.

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References

1. Fernstrom JD, Fernstrom MH. Tyrosine, phenylalanine, and catecholamine synthesis and function in the brain. J Nutr. 2007;137(6 Suppl 1):1539S-1547S. PubMed
2. Jongkees BJ, et al. Effect of tyrosine supplementation on clinical and healthy populations under stress or cognitive demands—a review. J Psychiatr Res. 2015;70:50-57. PubMed
3. Hase A, et al. Behavioral and cognitive effects of tyrosine intake in healthy human adults. Pharmacol Biochem Behav. 2015;133:1-6. PubMed
4. Mahoney CR, et al. Tyrosine supplementation mitigates working memory decrements during cold exposure. Physiol Behav. 2007;92(4):575-582. PubMed
5. Neri DF, et al. The effects of tyrosine on cognitive performance during extended wakefulness. Aviat Space Environ Med. 1995;66(4):313-319. PubMed
6. Thomas JR, et al. Tyrosine improves working memory in a multitasking environment. Pharmacol Biochem Behav. 1999;64(3):495-500. PubMed
7. Steenbergen L, et al. Tyrosine promotes cognitive flexibility: evidence from proactive vs. reactive control during task switching performance. Neuropsychologia. 2015;69:50-55. PubMed
8. van de Rest O, et al. Dose-dependent effects of oral tyrosine administration on plasma tyrosine levels and cognition in aging. Nutrients. 2017;9(12):1279. PubMed
9. Reimherr FW, et al. An open trial of L-tyrosine in the treatment of attention deficit disorder, residual type. Am J Psychiatry. 1987;144(8):1071-1073. PubMed
10. Young C, Arvan P. Substrate for thyroid hormone synthesis: biochemistry, evolution, and physiology. FASEB J. 2026;40(8):e71801. PubMed
11. Turner EH, et al. Serotonin a la carte: supplementation with the serotonin precursor 5-hydroxytryptophan. Pharmacol Ther. 2006;109(3):325-338. PubMed
12. Hidese S, et al. Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial. Nutrients. 2019;11(10):2362. PubMed
13. Magnusson I, et al. N-acetyl-L-tyrosine and N-acetyl-L-cysteine as tyrosine and cysteine precursors during intravenous infusion in humans. Metabolism. 1989;38(10):957-961. PubMed
14. Hoffer LJ, et al. N-acetyl-L-tyrosine as a tyrosine source in adult parenteral nutrition. JPEN J Parenter Enteral Nutr. 2003;27(6):419-422. PubMed
15. Topall G, Laborit H. Brain tyrosine increases after treating with prodrugs: comparison with tyrosine. J Pharm Pharmacol. 1989;41(11):789-791. PubMed