L-tyrosine is a nonessential amino acid (protein building block) that the body synthesizes from phenylalanine, another amino acid. Tyrosine is important to the structure of almost all proteins in the body. It is also the precursor of several neurotransmitters, including L-dopa, dopamine, norepinephrine, and epinephrine.

What Are Star Ratings?

This supplement has been used in connection with the following health conditions:

Used forWhy
3 Stars
150 mg for every 2.2 lbs (1 kg) of body weight, split into two doses taken before stressful activitiy (take the second dose 40 to 90 minutes after the first)
Occasionally taking this amino acid before a stressful activity may help maintain your mental capacity.

is an amino acid used by the body to produce certain adrenal stress hormones and chemical messengers in the nervous system (neurotransmitters). Animal research shows that brain levels of these substances decline with stress, and that giving animals tyrosine supplements reverses this decline and improves various tests of performance in stressed animals. In a controlled study, a protein drink containing 10 grams per day of tyrosine was more effective than a carbohydrate drink for improving mental performance scores in a group of cadets taking a stressful six-day combat training course. A double-blind trial in humans found that one-time administration of 150 mg of tyrosine per 2.2 pounds of body weight helped prevent a decline in mental performance for about three hours during a night of sleep deprivation. Single administrations of tyrosine (100 to 150 mg per 2.2 pounds of body weight) have also helped preserve mental performance during physically stressful conditions such as noise or extreme cold in several controlled studies.

2 Stars
Consult your doctor
Some people with depression have been found to improve with tyrosine.

The amino acid can be converted into norepinephrine, a neurotransmitter that affects mood. Women taking oral contraceptives have lower levels of tyrosine, and some researchers think this might be related to depression caused by birth control pills. L-tyrosine metabolism may also be abnormal in other depressed people and preliminary research suggests supplementation might help. Several doctors recommend a 12-week trial of L-tyrosine supplementation for people who are depressed. Published research has used a very high amount—100 mg per 2.2 pounds of body weight (or about 7 grams per day for an average adult). It is not known whether such high amounts are necessary to produce an antidepressant effect.

2 Stars
Consult a qualified healthcare practitioner
Supplementing with L-Tyrosine may help prevent a deficiency caused by the PKU diet and improve behavoir.
PKU results from a deficiency or malfunction of the enzyme, phenylalanine hydroxylase, which converts phenylalanine to . People with PKU have elevated concentrations of phenylalanine and low levels of L-tyrosine, which may contribute to behavior problems. In addition, low L-tyrosine levels in women with PKU may contribute to fetal damage. In some, but not all, double-blind studies, keeping L-tyrosine levels in the normal range by adding supplemental L-tyrosine to the diet improved behavior. In a preliminary study, blood L-tyrosine levels fluctuated significantly in people with PKU, suggesting a need for careful laboratory monitoring of people supplementing with L-tyrosine.
1 Star
Alcohol Withdrawal (Glutamine, Multivitamin, Phenylalanine, L-Tryptophan)
Refer to label instructions
In double-blind research, alcoholics treated with L-tyrosine combined with DLPA (D,L-phenylalanine), L-glutamine, prescription L-tryptophan, plus a multivitamin had reduced withdrawal symptoms and decreased stress.

Kenneth Blum and researchers at the University of Texas have examined neurotransmitter deficiencies in alcoholics. Neurotransmitters are the chemicals the body makes to allow nerve cells to pass messages (of pain, touch, thought, etc.) from cell to cell. Amino acids are the precursors of these neurotransmitters. In double-blind research, a group of alcoholics were treated with 1.5 grams of D,L-phenylalanine (DLPA), 900 mg of , 300 mg of L-glutamine, and 400 mg of L-tryptophan (now available only by prescription) per day, plus a multivitamin-mineral supplement. This nutritional supplement regimen led to a significant reduction in withdrawal symptoms and decreased stress in alcoholics compared to the effects of placebo.

1 Star
Parkinson’s Disease
Refer to label instructions
L-tyrosine is the direct precursor to L-dopa and therefore could be an alternative to L-dopa therapy, however, it should not be taken with L-dopa as it may interfere with L-dopa transport to the brain.

is the direct precursor to L-dopa. Theoretically, supplementing L-tyrosine could be an alternative to L-dopa therapy; however, L-tyrosine should not be taken with L-dopa as it may interfere with the transport of L-dopa to the brain. One small preliminary trial demonstrated that some people with Parkinson’s disease who supplemented with L-tyrosine (45 mg per pound of body weight) for three years had better clinical results and fewer side effects than did patients using L-dopa. Until these findings are confirmed, should not be used as a replacement for, or in addition to, L-dopa.

How It Works

How to Use It

Most people should not supplement with L-tyrosine. Some human research with people suffering from a variety of conditions used 100 mg per 2.2 pounds of body weight, equivalent to about 7 grams per day for an average-sized person. The appropriate amount to use in people with PKU is not known, therefore, the monitoring of blood levels by a physician is recommended.

Where to Find It

Dairy products, meats, fish, wheat, oats, and most other protein-containing foods contain tyrosine.

Possible Deficiencies

Some people affected by PKU are deficient in tyrosine. Tyrosine levels are occasionally low in depressed people.1 Any person losing large amounts of protein, such as those with some kidney diseases, may be deficient in several amino acids, including tyrosine.2


Interactions with Supplements, Foods, & Other Compounds

Vitamin B6, folic acid, and copper are necessary for conversion of L-tyrosine into neurotransmitters.

Interactions with Medicines

As of the last update, we found no reported interactions between this supplement and medicines. It is possible that unknown interactions exist. If you take medication, always discuss the potential risks and benefits of adding a new supplement with your doctor or pharmacist.
The Drug-Nutrient Interactions table may not include every possible interaction. Taking medicines with meals, on an empty stomach, or with alcohol may influence their effects. For details, refer to the manufacturers’ package information as these are not covered in this table. If you take medications, always discuss the potential risks and benefits of adding a supplement with your doctor or pharmacist.

Side Effects

Side Effects

L-tyrosine has not been reported to cause any serious side effects. However, it is not known whether long-term use of L-tyrosine, particularly in large amounts (such as more than 1,000 mg per day) is safe. For that reason, long-term use of L-tyrosine should be monitored by a doctor.


1. Chiaroni P, Azorin JM, Bovier P, et al. A multivariate analysis of red blood cell membrane transports and plasma levels of L-tyrosine and L-tryptophan in depressed patients before treatment and after clinical improvement. Neuropsychobiology 1990;23:1-7.

2. Alvestrand A, Ahlberg M, Forst P, Bergstrom J. Clinical results of long-term treatment with a low protein diet and a new amino acid preparation in patients with chronic uremia. Clin Nephrol 1983;19:67-73.

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