Guide
Who should not take L-tyrosine?
L-tyrosine lacks dedicated safety research in pregnancy, breastfeeding and children. Because it's a metabolic building block for both catecholamine neurotransmitters and thyroid hormone, people with a thyroid condition, a mood or neurological condition, or taking certain medications should ask a doctor first.
L-tyrosine hasn't been studied for safety in pregnancy, breastfeeding, or children, so the honest default for those groups is to ask a doctor rather than rely on a general guide. Because tyrosine is a building block for both catecholamine neurotransmitters and thyroid hormone, a handful of other groups have a specific, mechanism-based reason to check first too.
| Situation | Why it matters |
|---|---|
| Pregnant or breastfeeding | No published safety data exists in this population |
| Children | No dosing or safety research exists for children |
| A thyroid condition, or taking thyroid medication | Tyrosine is a building block for thyroid hormone |
| Low blood pressure, or taking blood pressure medication | Two trials found a modest decrease in blood pressure with tyrosine |
| Taking a medication affecting dopamine or norepinephrine (certain antidepressants, stimulant medications, an MAOI) | Tyrosine is the metabolic precursor of those same neurotransmitters |
| Kidney or liver disease | No dedicated research exists either way |
Pregnancy and breastfeeding
No dedicated safety research exists on L-tyrosine supplementation in pregnant or breastfeeding people or their infants. That's an absence of evidence, not evidence of safety. Ask a doctor before use in either situation.
Children
No dosing or safety research exists for tyrosine supplementation in children, so there's no dose or use guidance to give for that age group. Ask a doctor or pediatrician before giving a child any tyrosine product.
A thyroid condition, or thyroid medication
Tyrosine is one of the two raw materials — alongside iodine — the thyroid gland uses to build thyroid hormone. That's a fact about the biochemistry, not evidence that supplementing with tyrosine changes thyroid function; we found no controlled trial testing that question directly. Given the shared pathway, anyone with an underactive or overactive thyroid, or taking thyroid replacement medication, should ask a doctor before adding a tyrosine supplement.
Blood pressure
A 1994 trial found a single dose of tyrosine briefly lowered diastolic blood pressure before returning to baseline within an hour (PMID 8293316), and a 1999 field trial found systolic blood pressure had decreased after 5 days of daily use compared with a carbohydrate drink (PMID 10230711). Both trials were in healthy adults, not people managed for a blood pressure condition. If you have low blood pressure, or take a blood pressure medication, mention this pattern to a doctor before adding tyrosine.
Medications affecting dopamine or norepinephrine
Because tyrosine is the metabolic precursor of dopamine and norepinephrine, anyone taking a medication that works on those same systems — certain antidepressants, a stimulant medication, levodopa, or a monoamine oxidase inhibitor (MAOI) — should ask a doctor before adding it. See L-tyrosine and medications: what to check for the specific categories and why each one matters.
Kidney or liver disease
No dedicated research has tested tyrosine supplementation specifically in people with kidney or liver disease. That's an absence of evidence, not evidence of safety — ask a doctor before adding it if either applies to you.
Who this doesn't apply to
Outside the groups above, the research doesn't identify a documented reason for an otherwise healthy adult to avoid L-tyrosine — though it also doesn't establish a broad benefit at typical doses, covered in L-tyrosine benefits: what the research does and doesn't show.
Questions people ask
Who should not take L-tyrosine?
People who are pregnant or breastfeeding, children, anyone with a thyroid condition or on thyroid medication, anyone with low blood pressure or on blood pressure medication, and anyone taking a medication affecting dopamine or norepinephrine should check with a doctor first — none of those groups has dedicated tyrosine research to rely on instead.
Who should take L-tyrosine?
This page covers who should check with a doctor first, not who should take it — see L-tyrosine benefits: what the research does and doesn't show for what the research on healthy adults actually found, and its limits.
What should you not take with L-tyrosine?
See L-tyrosine and medications: what to check for the specific medication categories with a documented or mechanism-based reason for caution.
Related reading: L-tyrosine side effects, L-tyrosine and medications: what to check, and L-tyrosine benefits: what the research does and doesn't show.
Sources
- Effect of tyrosine on cognitive function and blood pressure under stress A 1994 crossover trial in 16 healthy adults found a single 100 mg/kg dose of tyrosine improved performance on two stress-sensitive cognitive tasks under noise stress, with a brief, early dip in diastolic blood pressure and no effect on mood, systolic blood pressure or heart rate.
- Tyrosine improves cognitive performance and reduces blood pressure in cadets after one week of a combat training course A 1999 field trial gave 21 military cadets either 2 g/day of tyrosine or a calorie-matched carbohydrate drink for 5 days during a combat training course; the tyrosine group performed better on memory and tracking tasks and had lower systolic blood pressure, with no difference in mood.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.