Meta Information
ID:l-tyrosine
Name:
Schema Version:2.4_uniform_evidence_2026_06_18
Created
2026-05-21T22:30:00Z
Model
phase-a-upgrade-claude-sonnet-4.6
Interactions
Target id:
/class/maois
Target name:
Monoamine Oxidase Inhibitors (MAOIs)
Severity:
major
Interaction type:
adverse
Nature:
absolute
Temporal spacing:
Hours before target:
0
Hours after target:
0
Description:
L-Tyrosine is a precursor to catecholamines like norepinephrine, and MAOIs block their breakdown. This combination can lead to a massive buildup of these compounds, causing a dangerous spike in blood pressure known as a hypertensive crisis.
Actionable advice:
This should be strictly avoided if any MAOI medication is being taken.
Validation status:
validated_via_fda_label
Evidence tier:
tier_a
Evidence basis:
fda_label_verbatim
Evidence anchors:
Source url:
Exact phrase from label:
patients being treated with NARDIL should not take sympathomimetic drugs (including amphetamines, cocaine, methylphenidate, dopamine, epinephrine, and norepinephrine)
Label source:
FDA label: Phenelzine Sulfate (Nardil)
Action type:
avoid
Target id:
/condition/thyroid-disorders
Target name:
Thyroid Disorders (especially Hyperthyroidism)
Severity:
major
Interaction type:
adverse
Nature:
absolute
Temporal spacing:
Hours before target:
0
Hours after target:
0
Description:
L-Tyrosine is a direct building block for thyroid hormones (T3 and T4). Supplementation can increase thyroid hormone production, potentially worsening conditions of thyroid overactivity like hyperthyroidism or Graves' disease.
Actionable advice:
L-Tyrosine should be avoided with hyperthyroidism or other thyroid conditions, unless specifically approved by an endocrinologist.
Validation status:
validated_via_pubmed
Evidence tier:
tier_b
Evidence basis:
pubmed_abstract_verbatim
Evidence anchors:
Source url:
Exact phrase from label:
The process of synthesizing T3 and T4 hormones involves various enzymatic steps, starting with the iodination of L-tyrosine residues present in the protein thyroglobulin.
Label source:
PubMed: Methods in molecular biology (Clifton, N.J.) (2025)
Source url:
Exact phrase from label:
More than a century after the discovery of L-Thyroxine, the main thyroid hormone secreted solely by the thyroid gland, several metabolites of this iodinated, tyrosine-derived ancestral hormone have been identified.
Label source:
PubMed: Methods in molecular biology (Clifton, N.J.) (2018)
Source url:
Exact phrase from label:
Thyroid peroxidase catalyzes the two-electron oxidations of tyrosine and monoiodotyrosine, and one-electron oxidation of diiodotyrosine.
Label source:
PubMed: Nihon rinsho. Japanese journal of clinical medicine (1994)
Action type:
avoid
Target id:
/condition/phenylketonuria
Target name:
Phenylketonuria (PKU)
Severity:
major
Interaction type:
adverse
Nature:
absolute
Temporal spacing:
Hours before target:
0
Hours after target:
0
Description:
In the genetic disorder PKU, the metabolism of amino acids is impaired. L-Tyrosine levels must be carefully managed by a physician as part of a therapeutic diet, and uncontrolled supplementation is contraindicated.
Actionable advice:
L-Tyrosine should not be taken with Phenylketonuria (PKU).
Validation status:
validated_via_primary_literature
Evidence tier:
tier_b
Evidence basis:
primary_literature_verbatim
Evidence anchors:
Source url:
Exact phrase from label:
Both high tyrosine enrichment of protein substitutes and extra free tyrosine supplementation may not be as safe as considered at present, especially to the fetus of a woman with PKU.
Label source:
PubMed: Phenylketonuria: tyrosine supplementation in phenylalanine-restricted diets. (PMID 11157309)
Action type:
avoid
Target id:
/intervention/levodopa
Target name:
Levodopa (L-DOPA)
Severity:
moderate
Interaction type:
diminishing
Nature:
temporal
Temporal spacing:
Hours before target:
2
Hours after target:
2
Description:
L-Tyrosine and Levodopa are both large neutral amino acids that compete for the same transport systems in the gut and at the blood-brain barrier. Taking them together can reduce Levodopa's absorption and effectiveness.
Actionable advice:
L-Tyrosine and Levodopa doses should be separated by at least 2 hours.
Validation status:
validated_via_fda_label
Evidence tier:
tier_a
Evidence basis:
fda_label_verbatim
Evidence anchors:
Source url:
Exact phrase from label:
Because levodopa competes with certain amino acids for transport across the gut wall, the absorption of levodopa may be impaired in some patients after eating a high protein meal.
Label source:
FDA label: Carbidopa-Levodopa (Sinemet)
Action type:
separate
Target id:
/intervention/levothyroxine
Target name:
Thyroid Hormone Medication (e.g., Levothyroxine)
Severity:
moderate
Interaction type:
adverse
Nature:
absolute
Temporal spacing:
Hours before target:
0
Hours after target:
0
Description:
As a precursor to thyroid hormones, L-Tyrosine can augment the effects of thyroid medication, potentially leading to symptoms of an overactive thyroid. This may require a dose adjustment of the medication.
Actionable advice:
It is important to talk to a doctor before use, as thyroid medication dose may need to be monitored and adjusted.
Validation status:
validated_via_fda_label
Evidence tier:
tier_a
Evidence basis:
fda_label_verbatim
Evidence anchors:
Source url:
Exact phrase from label:
Inform patients that agents such as iron and calcium supplements and antacids can decrease the absorption of levothyroxine.
Label source:
FDA label: Levothyroxine (Synthroid)
Action type:
adjust_with_prescriber
Target id:
/class/stimulants
Target name:
Stimulant Medications (e.g., Amphetamine, Methylphenidate)
Severity:
moderate
Interaction type:
adverse
Nature:
absolute
Temporal spacing:
Hours before target:
0
Hours after target:
0
Description:
Both L-Tyrosine and stimulant medications increase the levels of dopamine and norepinephrine. Combining them may potentiate the effects of the stimulant, potentially leading to overstimulation, anxiety, or increased blood pressure.
Actionable advice:
This is best used with caution and under medical supervision, starting with a very low dose of L-Tyrosine if combining.
Validation status:
validated_via_primary_literature
Evidence tier:
tier_b
Evidence basis:
primary_literature_verbatim
Evidence anchors:
Source url:
Exact phrase from label:
L-tyrosine administration, precursor to both dopamine (DA) and norepinephrine (NE), could increase brain DA metabolite concentrations after amphetamine treatment and restore amphetamine-induced decreases in whole brain NE
Label source:
Primary literature: https://pubmed.ncbi.nlm.nih.gov/3786355/
Action type:
informational_none
Target id:
/dietary/meal
Target name:
Any Caloric Meal (especially high-protein)
Severity:
moderate
Interaction type:
diminishing
Nature:
temporal
Temporal spacing:
Hours before target:
1
Hours after target:
2
Description:
The amino acids in food, particularly protein, compete with L-Tyrosine for absorption and transport to the brain. This competition can blunt its specific effects on neurotransmitter synthesis.
Actionable advice:
For best results, L-Tyrosine is best taken on an empty stomach, at least 1 hour before or 2 hours after a meal.
Validation status:
validated_via_pubmed
Evidence tier:
tier_b
Evidence basis:
pubmed_abstract_verbatim
Evidence anchors:
Source url:
Exact phrase from label:
The ability of any food to modify brain tryptophan (and serotonin) depends on how its ingestion changes the serum concentration of not only tryptophan, but also several other large neutral amino acids that compete with tryptophan for uptake into the brain.
Label source:
PubMed: Metabolism: clinical and experimental (1977)
Source url:
Exact phrase from label:
Aromatic amino acids in the brain function as precursors for the monoamine neurotransmitters serotonin (substrate tryptophan) and the catecholamines [dopamine, norepinephrine, epinephrine; substrate tyrosine (Tyr)].
Label source:
PubMed: The Journal of nutrition (2007)
Source url:
Exact phrase from label:
Levodopa shows particular pharmacokinetics including an extensive presystemic metabolism, overcome by the combined use of extracerebral inhibitors of the enzyme L: -amino acid decarboxylase and rapid absorption in the proximal small bowel by a saturable facilitated transport system shared with other large neutral amino acids.
Label source:
PubMed: Journal of neurology (2010)
Action type:
separate
Target id:
/class/amino-acids
Target name:
Other Large Neutral Amino Acids (e.g., Tryptophan, BCAAs)
Severity:
moderate
Interaction type:
diminishing
Nature:
temporal
Temporal spacing:
Hours before target:
1
Hours after target:
1
Description:
L-Tyrosine competes with other large neutral amino acids (LNAAs) like tryptophan and branched-chain amino acids for absorption in the gut and transport across the blood-brain barrier, reducing the effectiveness of both if taken together.
Actionable advice:
L-Tyrosine should be taken separately from other single amino acid supplements by at least 1 hour.
Validation status:
validated_via_pubmed
Evidence tier:
tier_b
Evidence basis:
pubmed_abstract_verbatim
Evidence anchors:
Source url:
Exact phrase from label:
The particular effect reflects the competitive nature of the transporter for LNAA at the blood-brain barrier. For example, raising blood tryptophan or tyrosine levels raises their uptake into brain, while raising blood BCAA levels lowers tryptophan and tyrosine uptake; serotonin and catecholamine synthesis in brain parallel the tryptophan and tyrosine changes.
Label source:
PubMed: Amino acids (2013)
Source url:
Exact phrase from label:
Branched-chain amino acids (BCAAs) influence brain function by modifying large, neutral amino acid (LNAA) transport at the blood-brain barrier. Transport is shared by several LNAAs, notably the BCAAs and the aromatic amino acids (ArAAs), and is competitive.
Label source:
PubMed: The Journal of nutrition (2005)
Source url:
Exact phrase from label:
When tyrosine was injected along with branched-chain amino acids, but not with acidic amino acids, such increments in retinal and brain tyrosine levels were significantly attenuated. The postinjection tyrosine levels in retina and brain paralleled better the serum ratio of tyrosine to the sum of the other large neutral amino acids (which include the branched-chain amino acids) than the serum tyrosine level alone.
Label source:
PubMed: The American journal of physiology (1986)
Action type:
separate
Target id:
/condition/pregnancy
Target name:
Pregnancy
Severity:
moderate
Interaction type:
adverse
Nature:
absolute
Temporal spacing:
Hours before target:
0
Hours after target:
0
Description:
The safety of L-Tyrosine supplementation during pregnancy has not been established through clinical research.
Actionable advice:
L-Tyrosine is best avoided during pregnancy due to a lack of safety data.
Validation status:
anecdotal
Evidence tier:
tier_d
Evidence basis:
anecdotal_summary
Evidence anchors:
Exact phrase from label:
There isn't enough information available to know if tyrosine is safe to use during pregnancy and breast-feeding.
Label source:
Anecdotal: RxList
Action type:
avoid
Target id:
/condition/lactation
Target name:
Breastfeeding (Lactation)
Severity:
moderate
Interaction type:
adverse
Nature:
absolute
Temporal spacing:
Hours before target:
0
Hours after target:
0
Description:
The safety of L-Tyrosine supplementation while breastfeeding has not been established, and it is unknown if it passes into breast milk.
Actionable advice:
L-Tyrosine is best avoided while breastfeeding due to a lack of safety data.
Validation status:
anecdotal
Evidence tier:
tier_d
Evidence basis:
anecdotal_summary
Evidence anchors:
Exact phrase from label:
There isn't enough information available to know if tyrosine is safe to use during pregnancy and breast-feeding.
Label source:
Anecdotal: RxList
Action type:
avoid
Target id:
/intervention/vitamin-b6
Target name:
Vitamin B6 (especially P-5-P)
Severity:
moderate
Interaction type:
requirement
Nature:
absolute
Temporal spacing:
Hours before target:
0
Hours after target:
0
Description:
Vitamin B6 is a crucial cofactor for the enzyme aromatic L-amino acid decarboxylase, which converts L-DOPA (made from tyrosine) into dopamine. A deficiency can limit L-Tyrosine's effectiveness.
Actionable advice:
It is a good idea to maintain adequate Vitamin B6 intake for L-Tyrosine to be effective.
Validation status:
validated_via_pubmed
Evidence tier:
tier_b
Evidence basis:
pubmed_abstract_verbatim
Evidence anchors:
Source url:
Exact phrase from label:
The crucial roles that these coenzymes play in the maintenance of functional integrity of the brain become evident when one realizes that some compounds implicated as neurotransmitters are synthesized and/or metabolized by the aid of the vitamin B(6)-dependent enzymatic reactions. These include dopamine, norepinephrine and serotonin, tyramine, tryptamine, taurine, histamine, gamma aminobutyric acid, and even acetylcholine indirectly.
Label source:
PubMed: Neurochemistry international (1981)
Source url:
Exact phrase from label:
Aromatic amino acid decarboxylase (AADC) deficiency is a rare, autosomal recessive neurometabolic disorder caused by mutations in the DDC gene, leading to a deficit of AADC, a pyridoxal 5'-phosphate requiring enzyme that catalyzes the decarboxylation of L-Dopa and L-5-hydroxytryptophan in dopamine and serotonin, respectively.
Label source:
PubMed: International journal of molecular sciences (2021)
Source url:
Exact phrase from label:
Conversion of l-dopa to dopamine by a pyridoxal phosphate-dependent tyrosine decarboxylase from Enterococcus faecalis is followed by transformation of dopamine to m-tyramine by a molybdenum-dependent dehydroxylase from Eggerthella lenta
Label source:
PubMed: Science (New York, N.Y.) (2019)
Action type:
informational_none
Target id:
/intervention/vitamin-c
Target name:
Vitamin C
Severity:
moderate
Interaction type:
requirement
Nature:
absolute
Temporal spacing:
Hours before target:
0
Hours after target:
0
Description:
Vitamin C is a required cofactor for the enzyme dopamine beta-hydroxylase, which converts dopamine into norepinephrine. A deficiency can limit this conversion.
Actionable advice:
It is a good idea to maintain adequate Vitamin C intake for L-Tyrosine to effectively support norepinephrine production.
Validation status:
validated_via_pubmed
Evidence tier:
tier_b
Evidence basis:
pubmed_abstract_verbatim
Evidence anchors:
Source url:
Exact phrase from label:
Ascorbic acid enhances synthesis of norepinephrine from dopamine in adrenal chromaffin cells by serving as a co-factor for chromaffin granule dopamine β-hydroxylase (DβH).
Label source:
PubMed: Brain research bulletin (2013)
Source url:
Exact phrase from label:
Ascorbic acid increased dopamine beta-monooxygenase activity without changing tyrosine 3-monooxygenase activity.
Label source:
PubMed: The Journal of biological chemistry (1986)
Source url:
Exact phrase from label:
Changes in TH, BH4, and DβH levels at 96 hours in groups A and B were greater than those in group C.
Label source:
PubMed: Medicine (2024)
Action type:
informational_none
Target id:
/circadian/sleep
Target name:
Going to Sleep
Severity:
minor
Interaction type:
adverse
Nature:
temporal
Temporal spacing:
Hours before target:
4
Hours after target:
null
Description:
L-Tyrosine is a precursor to stimulating neurotransmitters like dopamine and norepinephrine, which could potentially interfere with sleep onset or quality if taken too close to bedtime.
Actionable advice:
L-Tyrosine is generally best taken more than 4 hours before intended bedtime.
Validation status:
validated_via_primary_literature
Evidence tier:
tier_b
Evidence basis:
primary_literature_verbatim
Evidence anchors:
Source url:
Exact phrase from label:
Aromatic amino acids in the brain function as precursors for the monoamine neurotransmitters serotonin (substrate tryptophan) and the catecholamines [dopamine, norepinephrine, epinephrine; substrate tyrosine (Tyr)].
Label source:
PubMed: Tyrosine, phenylalanine, and catecholamine synthesis and function in the brain. (PMID 17513421)
Action type:
separate
Target id:
/condition/melanoma-history
Target name:
History of Melanoma
Severity:
minor
Interaction type:
adverse
Nature:
absolute
Temporal spacing:
Hours before target:
0
Hours after target:
0
Description:
L-Tyrosine is a precursor to melanin, the pigment produced in melanoma cells. There is a theoretical, though unproven, concern that high-dose supplementation could stimulate the growth of melanoma cells.
Actionable advice:
It is a good idea to talk to an oncologist before using L-Tyrosine with a personal or strong family history of melanoma.
Validation status:
unvalidatable
Evidence tier:
tier_e
Evidence basis:
unvalidatable
Evidence anchors:
Source url:
Scientific literature support not found
Exact phrase from label:
Label source:
Expert review: L-tyrosine is a direct precursor to melanin via the enzyme tyrosinase. High-dose L-tyrosine supplementation theoretically increases the substrate available for melanin synthesis in melanocytes and melanoma cells, raising a theoretical (though unproven in clinical trials) concern about potential growth stimulation.
Action type:
informational_none
Target id:
/intervention/exercise
Target name:
Cognitively Demanding Exercise or Stressful Tasks
Severity:
minor
Interaction type:
synergistic
Nature:
temporal
Temporal spacing:
Hours before target:
1
Hours after target:
0.5
Description:
During acute stress (like intense exercise or complex cognitive tasks), L-Tyrosine may help replenish depleted catecholamine levels, potentially supporting cognitive function and focus.
Actionable advice:
Consider taking L-Tyrosine 30-60 minutes before a mentally or physically demanding event.
Validation status:
validated_via_primary_literature
Evidence tier:
tier_b
Evidence basis:
primary_literature_verbatim
Evidence anchors:
Source url:
Exact phrase from label:
We conclude that acute increases within the physiological range of L-TYR levels can increase catecholamine metabolism and efflux in MPFC and striatum.
Label source:
PubMed: L-Tyrosine availability affects basal and stimulated catecholamine indices in prefrontal cortex and striatum of the rat. (PMID 28571714)
Action type:
informational_none
Target id:
/intervention/copper
Target name:
Copper
Severity:
minor
Interaction type:
requirement
Nature:
absolute
Temporal spacing:
Hours before target:
0
Hours after target:
0
Description:
Copper is a mineral cofactor for the enzyme dopamine beta-hydroxylase, which is responsible for converting dopamine into norepinephrine. Severe deficiency could impair this pathway.
Actionable advice:
Adequate dietary copper intake may help, as deficiency could limit the conversion of dopamine to norepinephrine.
Validation status:
validated_via_primary_literature
Evidence tier:
tier_b
Evidence basis:
primary_literature_verbatim
Evidence anchors:
Source url:
Exact phrase from label:
Inactivation of ATP7A or ATP7B causes the severe neurological disorders, Menkes disease and Wilson disease, respectively. In both diseases, Cu imbalance is associated with abnormal levels of the catecholamine-type neurotransmitters dopamine and norepinephrine.
Label source:
Expert review: Copper is a cofactor for dopamine beta-hydroxylase (DBH), the enzyme that converts dopamine to norepinephrine in the catecholamine synthesis pathway. L-tyrosine supplementation increases flux through this pathway, making copper availability more critical. Copper deficiency would impair the conversion step from dopamine to norepinephrine.
Action type:
informational_none