L-tyrosine has some human research behind it for mental performance under stress or heavy mental workload, but it is not shown to work as an ADHD treatment. Your body makes tyrosine from phenylalanine and uses it to build proteins and to make dopamine and norepinephrine. The studies are small and their results are mixed, so treat any benefit as possible rather than proven.
Quick facts about L-tyrosine
| Item | What the research shows |
|---|---|
| What it is | A form of tyrosine, a non-essential amino acid the body makes from phenylalanine (Medical News Today’s L-tyrosine and ADHD article) |
| Forms | Tyrosine is also known as L-tyrosine. The 1994 schizophrenia trial gave it alongside the antipsychotic molindone. |
| Doses used in studies | 10 g per day in four divided doses (1994 schizophrenia trial). The retailer blog does not give doses for most of its cognitive trials. |
| Typical study length | From one hour after a single dose (a 1994 trial in healthy adults) to 3-week periods (the 1994 schizophrenia trial) |
| Main studied uses | Mental performance under stress, sleep loss or heavy workload; exercise in heat; schizophrenia (no clear benefit); ADHD (weak research) |
What the human studies show
Does L-tyrosine help brain fog or mental performance under stress?
This is the largest group of reports, but most of them come second-hand, from a retailer’s blog and a Medical News Today summary, and they are small trials in healthy adults. Medical News Today describes a 2015 review of 15 studies that found tyrosine may help memory, mainly in demanding situations such as extreme weather or heavy cognitive load. The participants in those studies did not have ADHD.
A retailer’s wellness blog describes several more trials. A 2015 double-blind, randomized trial in 22 healthy adults reported better cognitive flexibility with tyrosine. A 1994 trial in 16 healthy people reported better performance one hour after a dose on stress-sensitive tasks. A 1999 study reported help with working memory during multitasking. A 1995 study reported less performance decline in people kept awake for more than 24 hours. These trials were in healthy adults under stress, sleep loss or workload. Brain fog itself was not the thing studied.
For another ingredient page that lays out its studies the same way, see green tea extract benefits evidence.
Does it help with exercise in heat?
Results here conflict. A 2011 study of 11 healthy men, as described in the same blog, found better endurance in the heat after a tyrosine drink. A 2014 study found no effect on self-paced endurance in the heat. A 2016 study found no improvement in physical performance or cognition during exercise.
Schizophrenia trial (1994): no clear benefit
In this placebo-controlled, double-blind crossover trial in inpatients, 10 g per day of L-tyrosine was added to molindone for 3 weeks, then compared with placebo for 3 weeks. The trial found no statistically significant improvement on the rating scales used. Card-sorting and memory tests did not differ between the periods. Eye-tracking showed more saccadic intrusions during the tyrosine period, which the authors said suggested a possible central effect. (1994 schizophrenia trial)
ADHD research
Medical News Today says the research on ADHD is limited. A 2016 study found children with ADHD had normal blood levels of tyrosine and other amino acids, and it concluded that children should not receive amino acid supplementation to treat ADHD. A 2011 study reported positive results in children, but the publisher withdrew that paper and retracted the results. For adults, the article says there is no evidence that L-tyrosine is an effective ADHD treatment.
The standard ADHD treatments the article names are behavioral therapy and prescribed medicines. If you or a child has ADHD, bring this to the clinician who manages it.
Older trials: depression, Parkinson’s and thyroid
A retailer’s blog reports a small 1988 study that found tyrosine helpful in dopamine-deficient depression, and a 1990 double-blind trial that found it was not helpful for other forms of depression. It reports a 2014 Parkinson’s study that found no significant benefit. It also reports a 2007 placebo-controlled study in Antarctica that found lower TSH and better mood in winter with tyrosine. The blog notes there are few other studies on tyrosine and thyroid function.
What does L-tyrosine do to dopamine?
Medical News Today says L-tyrosine helps the body produce dopamine and norepinephrine, and it states that L-tyrosine does not deplete dopamine. That is a statement about how the body makes dopamine, not proof that it restores dopamine in people. The studies here do not compare tyrosine with foods or vitamins for dopamine, so ask a clinician or dietitian which options fit you.
Is L-tyrosine like a prescription ADHD medicine?
No. Medical News Today describes prescription stimulants as the most common ADHD medication, working by increasing dopamine and norepinephrine. L-tyrosine has no comparable trial showing it treats ADHD, and the article says there are no specific studies on it alongside ADHD medications. Do not swap one for the other.
Doses used in studies
These are the doses that researchers and blogs report. None is a recommendation.
| Use | Dose as reported | Notes |
|---|---|---|
| Schizophrenia trial, 1994 (added to molindone) | 10 g per day in four divided doses, for 3 weeks | Research dose; no benefit found on the rating scales used |
| Retailer blog’s list of common use | 500 to 1,000 mg once or twice a day for adults | A blog listing, not a study dose |
| Parkinson’s use described in the blog | 500 mg three times a day | The blog cites a 2014 study with no significant benefit |
Ask a clinician about any dose for your own situation.
Safety, side effects and medicine interactions
The 2002 review of L-tyrosine as a vaccine adjuvant, in allergy vaccines (2002 allergy-vaccine review), reported no toxicity in animal studies and said this supports the idea that L-tyrosine is safe for human use as an adjuvant. The review drew partly on unpublished data, and it concerns vaccines, not daily supplements. Local injection-site reactions occurred.
A retailer’s wellness blog says the FDA considers tyrosine “Generally Regarded As Safe” when taken as a supplement. You can read the cited FDA regulation, FDA regulation 21 CFR 172.320, directly. Use these interaction notes to start a conversation with your prescriber.
| Topic | What the sources say |
|---|---|
| MAOI antidepressants | Medical News Today says to avoid L-tyrosine if you take MAOIs. Tyrosine breaks down into tyramine, and it is not known whether the supplement causes tyramine to build up. A 2014 article on this was retracted in 2021. |
| Thyroid medicines | The article says the concern is that it could lead to too much thyroid hormone. More up-to-date research is needed. |
| Parkinson’s medication | The blog says to take the two separately because they compete for absorption in the gut, and to talk to your doctor. |
| ADHD medicines | There are no specific studies on combining L-tyrosine with ADHD medicines. |
| PKU | The blog says PKU is a rare condition in which the enzyme needed to convert phenylalanine into tyrosine is missing. |
Who should talk to a clinician first
- Anyone taking an MAOI (a monoamine oxidase inhibitor), who should avoid L-tyrosine according to Medical News Today and should check with a doctor first.
- Anyone taking thyroid medicine.
- Anyone taking Parkinson’s medication.
- Anyone taking an ADHD medicine, or anyone considering L-tyrosine for ADHD in themselves or a child.
- Anyone with PKU.
Do not change a prescribed medicine because of this page. Talk to the prescriber first.
What is still unknown
- Whether L-tyrosine helps ADHD in adults or children. Current research does not show it does, and the 2011 child study was retracted.
- Whether it helps brain fog. Brain fog was not the outcome in these trials.
- Whether the 2015 review applies to people with ADHD. Those participants were excluded.
- Whether it interacts with MAOIs. It is not known whether tyramine builds up.
- Long-term daily use. Most of these trials were short and small.
- The right dose for any person. No dose here is a recommendation.
If you want to know which foods or vitamins affect dopamine, ask a dietitian or your clinician.
How to read a label that lists L-tyrosine
- Find the name. Tyrosine is also known as L-tyrosine.
- Check the milligrams per serving. Compare that with the doses in the table above, including the 10 g used in the 1994 trial.
- Watch for blends. If the label gives only a total blend weight, ask the company for the amount of L-tyrosine before you order.
- Treat ADHD or focus claims on the label as the maker’s statements, and check them against the sections above. For a guide to weighing claims, read ingredient evidence vs marketing claims.
By ClinicalStudyConnect.com Research Desk