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Nutrient Name: Tyrosine.
Related Substance:L-Phenylalanine.

Summary Table
Drug/Class Interaction TypeMechanism and SignificanceManagement
Amphetamines Dextroamphetamine Methylphenidate
/ /
Tyrosine administration may enhance dopamine synthesis through its role as a precursor of L-dopa. Coadministration of L-tyrosine may reverse or prevent tyrosine depletion caused by amphetamines and support activity of amphetamine therapy by enhancing precursor availability. Adverse effects improbable. Research with well-designed trials warranted.Coadministration may enhance therapeutic outcomes within integrative strategy, particularly with tyrosine depletion. Supervise, monitor, and titrate.
Imipramine Tricyclic antidepressants (TCAs)

Tyrosine is a precursor to many neurotransmitters, including dopamine. Coadministration of tyrosine and L-tryptophan with imipramine may facilitate withdrawal in cocaine addiction. Evidence mixed and limited. Further research warranted.Consider coadministration with close supervision. Monitor and titrate.
Levodopa Antiparkinsonian medications
/ / / /
Tyrosine administration may enhance dopamine synthesis through its role as a recursor of L-dopa. L-Tyrosine may benefit Parkinson's patients. However, limited knowledge regarding potential issues of competition in absorption, transport system, and brain uptake suggests need for continued research.Consider coadministration with close supervision and regular monitoring.
Levothyroxine Thyroid hormones

L-Tyrosine is a precursor in endogenous synthesis of L-thyroxine. Additive interaction is probable from concomitant administration of exogenous thyroid hormone(s) and tyrosine, but possibly with minimal effect in individuals whose thyroid gland has atrophied from chronic use of synthetic thyroid medication. Adverse effects improbable. Research with well-designed trials examining various permutations warranted.Coadministration may be beneficial. Monitor and titrate.
Monoamine oxidase (MAO) inhibitors

MAO inhibitors can potentiate sympathomimetic substances and related compounds to induce a hypertensive crisis with potential risk of heart attack or stroke. Tyramine from food sources is usually implicated in such interactions, but tyramine can also be produced by intestinal bacteria from tyrosine through decarboxylation. This plausible but potentially dangerous interaction has not been confirmed by evidence from case reports or clinical trials.Avoid concomitant use, also L-tryptophan, 5-HTP, and phenylalanine.
Oral contraceptives (OCs)
/ /
Through effects on amino acid balance, exogenous estrogen and progestins can decrease plasma tyrosine levels, alter neurotransmitter levels, and potentially contribute to or exacerbate OC adverse effects, such as depression. Human research is limited and inadequate to determine occurrence of clinically relevant interactions or susceptibility factors. Adverse effects from coadministration improbable. Research with well-designed trials warranted.Coadministration, with B-complex vitamins, may be beneficial unless otherwise contraindicated. Consider support for liver conjugation functions. Supervise and monitor.
5-HTP , 5-Hydroxytryptophan.
nutrient description

Physiology and Function

Tyrosine is a conditionally essential amino acid normally synthesized from phenylalanine, which is an essential amino acid. Hepatic conversion ofL-phenylalanine toL-tyrosine can be impaired during infection, trauma, chronic illness, liver disease, or other forms of severe stress, thus making tyrosine a conditionally essential amino acid.

L-Tyrosine plays a critical role in the synthesis of neurotransmitters within the central nervous system (CNS). In particular, it serves as a precursor toL-dopa, dopamine, norepinephrine, and epinephrine, the brain concentrations of which depend on intake of tyrosine. The conversion ofL- tyrosine into these neurotransmitters requires vitamin B6, folic acid, and copper. Tyrosine also requires biopterin (a folate derivative), NADPH and NADH (metabolites of niacin), copper, and vitamin C. Tyrosine acts as an adaptogen through its role as a precursor of norepinephrine and epinephrine.

Several other key activities are among the known functions of tyrosine. Tyrosine is a precursor to thyroid hormones and catecholestrogens, compounds that have estrogen-like and catecholamine-like effects, as well as a constituent of amino sugars and amino lipids. It is also involved in the synthesis of enkephalins, important endogenous analgesic peptides in the endorphin family, and melanin, a pigment responsible for hair and skin color. Lastly, tyrosine binds free radicals and is considered a mild antioxidant.

nutrient in clinical practice

Known or Potential Therapeutic Uses

Common uses include depression, thyroid nutriture, and alcohol withdrawal support. Individuals with phenylketonuria (PKU) are often treated with tyrosine to compensate for inborn errors of phenylalanine metabolism and resultant tendency to tyrosine deficiency.

Historical/Ethnomedicine Precedent

Tyrosine has not been used historically as an isolated nutrient.

Possible Uses

Addictions, alcohol withdrawal support, Alzheimer's disease, attention deficit disorder, cardiovascular disease, chronic fatigue, cocaine abuse and withdrawal, cognitive enhancement, dementia, depression, excessive appetite, fatigue, hypotensive crisis, hypothyroidism, impotence, jet lag, low libido, narcolepsy, Parkinson's disease, premenstrual syndrome, schizophrenia, stress disorders, weight loss.

Deficiency Symptoms

Because tyrosine is a precursor to thyroid hormones and catecholamines, a deficiency may lead to impaired thyroid function as well as low adrenal function. Some research indicates that tyrosine levels may be low in some individuals with depression. A lack of melanin caused by a tyrosine deficiency could predispose a person to skin cancer. Anyone experiencing a pattern of protein loss, especially over an extended period (e.g., with nephrotic syndrome), may develop a deficiency in tyrosine and other amino acids.

Dietary Sources

Dietary sources richest in tyrosine are fish, meat, dairy, eggs, nuts, wheat germ, and oats. Normally, tyrosine can be synthesized endogenously fromL-phenylalanine.

Source of Supplemental Form

MostL-tyrosine in nutraceuticals is produced by bacterial fermentation processes in a growth medium, from which the amino acid is then purified.

Supplemental Form

Capsule, powder, tablet; solution, oral.

Tyrosine is best absorbed when ingested at least 30 minutes before meals, divided into three daily doses. Some manufacturers have claimed that acetyl-L-tyrosine (ALT) affects the brain more rapidly than any other form.

It is often recommended that tyrosine be taken together with a multivitamin-mineral complex because vitamins B6, folate, and copper participate in the conversion ofL-tyrosine into neurotransmitters.

Dosage Range



  • Recommended dietary intake (RDA): 7.3 mg/pound body weight/day, approximately 1 g/day
  • Average daily intake in United States: 3.5 to 5 g
  • Supplemental/Maintenance:   Supplementation is usually not necessary for most individuals. Optimal levels of intake have not been established.
  • Pharmacological/Therapeutic:   1 to 8 g/day.

Clinical trials have used 100 mg/kg body weight/day, which constitutes a large dose. When indicated, many health care providers experienced in nutritional therapeutics initiate treatment with 2 g per day and gradually increase the dose as appropriate. Use at therapeutic doses would typically be short term. The most common recommended dose is 500 to 1000 mg three times daily (before each of the three meals).

  • Toxic:   Usually not to exceed 12 g per day, the highest known safe level.

Pediatric (<18 Years)

Dietary: No specific dietary recommendation has been established for tyrosine in children.

Supplemental/Maintenance: Not currently recommended for children.

Pharmacological/Therapeutic: Indicated when amino acid imbalance demonstrated by laboratory assessment. In particular, tyrosine is administered in patients with PKU once plasma tyrosine levels have been controlled. Otherwise, specific treatment recommendations have not been established.

Toxic: No toxic dosage level established specifically for infants and children.

Laboratory Values

Range of normal plasma tyrosine levels:

  • Children: 26 to 110 µmol/L
  • Adults: 45 to 74 µmol/L

safety profile


L-Tyrosine is usually tolerated well by most adults and generally considered to be free of adverse effects for most individuals at usual dosage levels of 2 to 3 g daily.L-Tyrosine has very low toxicity.

Nutrient Adverse Effects

General Adverse Effects

Nausea, diarrhea, vomiting, and nervousness are the primary effects associated with intake of high dosage levels of tyrosine in some reports. Migraine headache, elevated blood pressure, and mild gastric upset may also result from excessive levels of tyrosine (or tyrosine-derived neurotransmitters such as dopamine).

Adverse Effects Among Specific Populations

Use of tyrosine may be contraindicated for individuals with hyperthyroidism, Tourette's syndrome, or schizophrenia, particularly when high brain dopamine levels are present. Exogenous tyrosine (or phenylalanine) administration could theoretically result in elevated brain dopamine levels and symptom aggravation.

Exogenous tyrosine could theoretically promote cancer cell division in susceptible individuals. Many tumor cells overexpress tyrosine kinase enzymes; phosphorylated tyrosine functions as a cell-signaling molecule that drives DNA synthesis, cell growth, and division in these tumors.

Pregnancy and Nursing

Evidence is lacking within the scientific literature to suggest or confirm any adverse effects related to fetal development during pregnancy or to infants who are breast-fed associated with tyrosine administration. Caution still advised regarding supplementation with free-formL-tyrosine.

Infants and Children

No adverse effects have been reported. However, sufficient research-based evidence is lacking to guarantee the safety of tyrosine in infants and children.


  • Migraine.
  • L-Tyrosine is contraindicated in those with the inborn errors of metabolism, alkaptonuria and tyrosinemia types I and II.
  • Tyrosine (and phenylalanine) should be avoided by individuals with cancer, especially pigmented melanoma.
  • Tyrosine should be avoided by individuals taking monoamine oxidase (MAO) inhibitors because of its role in synthesis of dopamine, norepinephrine, and epinephrine.
  • L-Tyrosine is contraindicated in those hypersensitive to any component of anL-tyrosine-containing supplement.

Precautions and Warnings

Concomitant administration of phenylalanine and tyrosine at high dosage levels should be avoided outside of professional supervision due to potential additive effects. Food sources may contain both nutrients but typically would be considered safe at usual levels of intake.

interactions review

Strategic Considerations

Tyrosine from direct dietary sources as well as that synthesized endogenously from phenylalanine provides adequate quantities for normal physiological functions in most healthy individuals with reasonable nutriture. Administration of tyrosine is uncommon in conventional medicine apart from prevention and treatment of tyrosine deficiency in individuals with PKU and occasionally as an adjunctive agent for individuals with Parkinson's disease. Oral dosage levels of 19.2 mg/kg daily, divided equally in meals, and 100 mg/kg daily in three divided doses are typical for PKU and Parkinson's patients, respectively. Prudent clinical management requires establishing controlled plasma tyrosine levels approximating the norm of 45 µmol/L before considering tyrosine administration. Furthermore, concomitant use of tyrosine and levodopa should be discouraged outside the context of medical supervision because levodopa may interfere with the absorption of tyrosine.

Although supportive evidence is largely inconclusive, many practitioners experienced in nutritional therapeutics routinely prescribeL-tyrosine, with other nutrients and botanicals, as part of a comprehensive strategy to support thyroxine, dopamine, and other neurotransmitters in the treatment of fatigue, depression, suboptimal thyroid function, and other conditions. Methods for establishing clinical indications and determining therapeutic response are largely anecdotal and unsystematic, with clinical research data limited and preliminary.

A review of the collective body of available evidence reveals several medications that may interact with tyrosine to produce clinically significant effects in certain patients. The potentially severe interaction with MAO inhibitors, including the risk of a hypertensive crisis and catastrophic sequelae, warrants a general contraindication of concomitant use. Physicians prescribing any of these medications should ask patients about supplemental use of tyrosine and advise that they be avoided or discontinued, except possibly under close supervision. However, most interactions involving tyrosine and conventional medications can be beneficial in appropriate circumstances, but usually warrant supervision, monitoring, and periodic adjustments. Thus, coadministration of tyrosine can often enhance clinical outcomes when used in conjunction with levodopa, levothyroxine, and oral contraceptives within an integrative strategy. Concomitant use with imipramine, mixed amphetamines, appetite suppressants, or opioid analgesics may be appropriate in some cases but requires close supervision and regular monitoring by health care providers trained and experienced in both conventional pharmacology and nutritional therapeutics. In many cases, tyrosine administration can work more effectively when complemented by folic acid, B vitamins, and other nutrients typically at suboptimal levels in the target patient populations, compromised with the primary pathology or comorbid conditions, depleted by typical medications, or otherwise supportive of the therapeutic intervention.

nutrient-drug interactions
Amphetamines and Related Stimulant Medications
Imipramine and Related Tricyclic Antidepressants (TCAs)
Levodopa and Related Antiparkinsonian Medications
Levothyroxine and Related Thyroid Hormones
Monoamine Oxidase (MAO) Inhibitors
Oral Contraceptives: Monophasic, Biphasic, and Triphasic Estrogen Preparations (Synthetic Estrogen and Progesterone Analogs)
theoretical, speculative, and preliminary interactions research, including overstated interactions claims
Appetite-Suppressant Medications, Including Amphetamine, Ephedrine, and Phenylpropanolamine
Codeine, Methadone, Morphine, and Related Oral Narcotic Analgesics (Opiates)
nutrient-nutrient interactions
5-Hydroxytryptophan (5-HTP)
Branched-Chain Amino Acids: Isoleucine, Leucine, Valine
Citations and Reference Literature
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