L-Tyrosine and medications.
L-Tyrosine is in the Distil supplement database, evidence Grade B. The page below lists every medication we have explicitly assessed it against.
L-tyrosine is an amino acid the body uses to make dopamine and noradrenaline, and it is also a building block for thyroid hormones. Its main supplement use is supporting cognitive performance under stress, where the evidence is Grade B from work by Colzato and Deijen; the ADHD case is weaker at Grade C. The usual dose is 500 to 2,000mg, taken as needed before demanding tasks or daily for ADHD support, starting low if you are sensitive to stimulants. The interactions here are the cautionary part. It must be avoided entirely with MAOIs, where the combination is serious. Because it raises dopamine and noradrenaline, it is also best avoided in bipolar disorder without psychiatric oversight, since boosting these can occasionally trigger mania or hypomania. Because it is a thyroid hormone precursor, it warrants monitoring alongside thyroid medication, and it competes with levodopa for absorption, so those should be separated. Anxiety-prone people should start at the low end, since tyrosine can worsen anxiety in some. Taken late it can disturb sleep, so earlier in the day is the practical default.
Below are the 15 documented pairs we have explicitly assessed for L-Tyrosine: 3 red and 12 amber. The pairs cluster around 5 mechanisms: MAOI pressor (blood-pressure surge), Antithyroid drug interference, Levodopa amino-acid transport competition, Additive sympathomimetic activity, and Additive thyroid-hormone effect. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not listed here is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by medication, and the missing-item form at the bottom of the page routes any uncatalogued medication into our next curation pass.
Documented interactions
Last reviewed 21 June 2026. Each interaction below lists the evidence its assessment drew on: some rest on studies of the exact pair, others on mechanism evidence, where a citation may support one part of the reasoning rather than the exact combination. The evidence line on each entry says which.
MAOI pressor (blood-pressure surge)
Red Does interact with Isocarboxazid?
Taking L-Tyrosine with isocarboxazid (an irreversible MAOI) may push blood pressure up sharply, because tyrosine is the raw material your body turns into adrenaline and noradrenaline and the MAOI blocks their breakdown, so we treat this as a do-not-combine pair without specialist sign-off.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Red Does interact with Phenelzine?
Taking L-Tyrosine with phenelzine (an irreversible MAOI) may push blood pressure up sharply, because tyrosine is the raw material your body turns into adrenaline and noradrenaline and the MAOI blocks their breakdown, so we treat this as a do-not-combine pair without specialist sign-off.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Red Does interact with Tranylcypromine?
L-tyrosine is a building block for noradrenaline and dopamine, and tranylcypromine is an MAOI that stops these from being broken down. Together they could drive blood pressure dangerously high (a hypertensive crisis). Tranylcypromine carries the strongest pressor risk of the MAOIs, so we treat this as a do-not-combine pair without specialist sign-off.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Linezolid?
Taking L-Tyrosine with linezolid could still nudge blood pressure up, because tyrosine is the raw material your body turns into adrenaline and noradrenaline and linezolid is an antibiotic that also acts as a reversible MAOI partly slowing their breakdown, though it carries less blood-pressure risk than the older irreversible MAOIs. Take this combination only with your prescriber's awareness, and not at high tyrosine doses.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Moclobemide?
Taking L-Tyrosine with moclobemide could still nudge blood pressure up, because tyrosine is the raw material your body turns into adrenaline and noradrenaline and moclobemide is a reversible MAOI that partly slows their breakdown, though it carries much less of the blood-pressure risk seen with the older irreversible MAOIs. Take this combination only with your prescriber's awareness, and not at high tyrosine doses.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Rasagiline?
Taking L-Tyrosine with rasagiline can in theory raise blood pressure, because tyrosine is the raw material the body turns into noradrenaline and adrenaline and rasagiline is an MAO-B inhibitor, though the risk is lower with a selective MAO-B drug than with the older non-selective MAOIs. Raise this with your prescriber and have blood pressure checked rather than starting on your own.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Selegiline?
Taking L-Tyrosine with selegiline can in theory raise blood pressure, because tyrosine is the raw material the body turns into noradrenaline and adrenaline and selegiline is an MAO-B inhibitor that can add its own pressor effect at higher doses. Raise this with your prescriber and have blood pressure checked rather than starting on your own.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Antithyroid drug interference
Amber Does interact with Carbimazole?
Carbimazole works by lowering an overactive thyroid. L-tyrosine is a building block of thyroid hormone and at high doses can nudge thyroid activity up, so in theory it could pull against carbimazole and make it a little less effective. This has not been tested in people on carbimazole, so it is a caution rather than a firm warning. If you take carbimazole, mention L-tyrosine to the clinician who manages your thyroid and keep to your usual thyroid blood tests.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Propylthiouracil?
Propylthiouracil works by lowering an overactive thyroid. L-tyrosine is a building block of thyroid hormone and at high doses can nudge thyroid activity up, so in theory it could pull against propylthiouracil and make it a little less effective. This has not been tested in people on propylthiouracil, so it is a caution rather than a firm warning. If you take propylthiouracil, mention L-tyrosine to the clinician who manages your thyroid and keep to your usual thyroid blood tests.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Levodopa amino-acid transport competition
Amber Does interact with Co-beneldopa (Benserazide/levodopa)?
Taking an L-Tyrosine supplement around the same time as co-beneldopa (Madopar, which contains levodopa) may blunt how well the medication works, because tyrosine and levodopa are both large amino acids that share the same carrier from the gut into the blood and into the brain. Separate any tyrosine supplement from your doses and discuss it with your Parkinson's team rather than adding it on your own.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Co-careldopa (Carbidopa/levodopa)?
Taking an L-Tyrosine supplement around the same time as co-careldopa (Sinemet, which contains levodopa) may blunt how well the medication works, because tyrosine and levodopa are both large amino acids that share the same carrier from the gut into the blood and into the brain. Separate any tyrosine supplement from your doses and discuss it with your Parkinson's team rather than adding it on your own.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Additive sympathomimetic activity
Amber Does interact with Dexamfetamine sulfate?
L-tyrosine is the raw material your body turns into dopamine and noradrenaline, the same brain chemicals dexamfetamine raises. Taking the two together could in theory add to a stimulant's effects, such as a faster heart rate, higher blood pressure, jitteriness or trouble sleeping, though supplemental tyrosine's effect on top of the medicine is likely to be modest. If you take a stimulant, mention any tyrosine supplement to your prescriber, start at a low dose, and keep an eye on your heart rate and how wired or restless you feel.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Lisdexamfetamine dimesylate?
L-tyrosine is the raw material your body turns into dopamine and noradrenaline, the same brain chemicals lisdexamfetamine raises. Taking the two together could in theory add to a stimulant's effects, such as a faster heart rate, higher blood pressure, jitteriness or trouble sleeping, though supplemental tyrosine's effect on top of the medicine is likely to be modest. If you take a stimulant, mention any tyrosine supplement to your prescriber, start at a low dose, and keep an eye on your heart rate and how wired or restless you feel.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Methylphenidate hydrochloride?
L-tyrosine is the raw material your body turns into dopamine and noradrenaline, the same brain chemicals an ADHD stimulant like methylphenidate raises. Taking the two together could in theory add to a stimulant's effects, such as a faster heart rate, higher blood pressure, jitteriness or trouble sleeping, though supplemental tyrosine's effect on top of the medicine is likely to be modest. If you take a stimulant, mention any tyrosine supplement to your prescriber, start at a low dose, and keep an eye on your heart rate and how wired or restless you feel rather than adding it on your own.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Additive thyroid-hormone effect
Amber Does interact with Levothyroxine?
L-tyrosine is one of the building blocks your body uses to make thyroid hormone, and a high-dose study found it can gently lower TSH and nudge thyroid activity up. On top of levothyroxine that effect could in theory add up and tip you towards having a little too much thyroid hormone, though this has not been tested in people who take levothyroxine. If you take both, mention the L-tyrosine to the clinician who manages your thyroid and ask for a TSH check so your dose can be reviewed if needed.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
What this list does not say. Pairs not flagged here are not implicitly safe. They are either not yet in our database, or fall outside our inclusion scope. Use the checker below to surface any medication, and submit a missing item if you take something we have not catalogued.
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The interaction check is one section of the full report. You also get the reasoning behind each recommendation and the evidence references used.
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