L-Tyrosine Side Effects & Adverse Reactions (List) (2024)

Tyrosine is a non-essential amino acid that was discovered in 1846 by Justus von Liebig, a German chemist. The word “tyrosine” is derived from the Greek term “tyros” – meaning “cheese.” L-Tyrosine is commonly taken in the form of a dietary supplement to facilitate catecholamine synthesis.

Upon ingestion of L-tyrosine, the body metabolizes it into catecholamines including: dopamine, norepinephrine, and epinephrine. These catecholamines are thought to modulate aspects of neurophysiological functioning such as: attention, cognition, energy, mood, memory, and vigilance. Individuals with suboptimal catecholamine synthesis may experience prominent deficits in various aspects of cognitive performance.

While one solution to increase catecholamine synthesis is to eat foods high in tyrosine (and phenylalanine) such as chicken, fish, and turkey – not everyone wants to make dietary alterations. A common method for increasing catecholamine synthesis is to regularly supplement with L-tyrosine. Supplementation of L-tyrosine is a quick, potent, and established method for increasing concentrations of beneficialneurotransmitters and preserving cognitive function. (Read: L-Tyrosine Benefits).

Despite the convenience of popping an L-tyrosinesupplement to promote catecholamine synthesis, supplementation may provoke unwanted side effects. While most L-tyrosine side effects are considered mild, they may be severe for certain individuals – triggering anxiety, heart rate changes, and/or headaches. It is important to understand these potential adverse reactions prior to supplementation with L-tyrosine.

Factors that influence L-Tyrosine side effects

It is important to realize that there are many factors that may influence the quantity and severity of side effects that you experience while taking L-tyrosine. These factors include things like: dosage, individual factors (e.g. neurophysiology), interactions, duration of supplementation, frequency of administration, and the specific source of L-tyrosine utilized.

1. Dosage (500 mg to 2000 mg)

There is a lack of medical guidelines to follow for L-tyrosine dosing. In many cases, dosing is subject to significant variation based on a person’s bodyweight. Some protocols call for administration of 100-150 mg/kg (bodyweight) per day. With bodyweight-based protocols, individuals with greater bodyweight end up taking more L-tyrosine than those who are lighter.

2. Individual variation

Many side effects from L-tyrosine are subject to individual variation. Two people could take the same dosage, yet one may attain significant therapeutic benefit without any noticeable side effects, while the other may experience headaches, nausea, and diarrhea. For this reason, it is important to consider your neurophysiology, genetics, and bodyweight as potentially influencing side effects from L-tyrosine supplementation.

For example, individuals with a disorder called “phenylketonuria” (PKU) are unable to metabolize phenylalanine (a precursor to tyrosine) as a result of genetic polymorphisms. To increase tyrosine levels, and ultimately catecholamine synthesis, these individuals need L-tyrosine supplements. It should be suggested that polymorphisms of certain genes could influence side effects.

While companies like GeneSight can predict individual side effects and responses to drugs, it is unclear as to whether they will expand their database to include supplements like L-tyrosine. In addition to genetics, a person’s neurophysiology (brain waves, neurochemistry, hormones, and arousal) may influence side effects associated with L-tyrosine supplementation. Other individual factors such as bodyweight, stress level, diet, sleep, and lifestyle may also influence responses to L-tyrosine.

3. Interactions

It is important to consider the possibility that certain L-tyrosine side effects may result from interactions with alcohol, drugs (illicit or pharmaceutical), or supplements. Many people take L-tyrosine along with certain medications and/or as part of a supplement “stack.” Whenever an individual co-administers L-tyrosine with another substance, it is difficult to understand whether side effects are specifically from: the L-tyrosine, the other substance, or an interaction effect.

4. Time Span + Frequency

Those that have taken L-tyrosine for a long-term may be more likely to experience side effects than someone taking it on a short-term. Most sources suggest that L-tyrosine is safe to supplement for up to 3 months (90 days), but it is unknown as to whether side effects and/or adverse reactions are more likely following several months. In addition to the duration over which a person has taken L-tyrosine, it is important to consider the frequency of administration.

Someone who takes L-tyrosine for a long-term, on an everyday daily basis (or multiple times per day) may be more likely to experience adverse reactions than someone who takes it for a short-term on an intermittent (“as needed”) basis. It should be noted that most research suggests short-term safety of L-tyrosine, but long-term effects remain unknown, especially when taken on a frequent basis.

Certain individuals may be more likely to experience more side effects when they first start taking L-tyrosine as a result of temporary physiological adaptation to the supplement. Others may find that they don’t experience any short-term side effects, but develop unwanted long-term effects from supplementation. Generally, tolerance is established over frequent, long-term administration of L-tyrosine – leading a person to increase the dose, which ultimately increases side effects.

5. Source & Formulation of L-tyrosine

It is important to consider that the source of L-tyrosine may influence the side effects a person experiences. Some people may find that a certain brand of L-tyrosine produces less side effects than another. In addition to consideration of the L-tyrosine brand and sourcing, the specific formulation may factor into the manifestation of side effects.

For example, some people may prefer to take N-Acetyl L-Tyrosine for enhanced absorption. This may allow them to take lower doses that are more efficiently metabolized by the body, leading to less noticeable side effects compared to an individual taking a standardized L-tyrosine supplement. There are many formulations of L-tyrosine, some of which may reduce the likelihood of side effects.

L-Tyrosine Side Effects & Adverse Reactions (List)

Below is a list of possible side effects that a person may experience when supplementing with L-tyrosine. Understand that the quantity and severity of side effects are likely to be influenced by the aforementioned factors. Realize that most people will not experience every single side effect on this list and that side effects are largely subject to individual variation.

Most common side effects associated with L-tyrosine supplementation include: heart rate changes, headaches, stomach aches, and increased anxiety. It is unknown as to whether long-term supplementation is safe. If you develop any of these side effects, it is recommended to consult a medical professional.

Abnormal heart rate: Many people notice that their heart rate increases and/or becomes abnormal upon supplementation of L-tyrosine. This is due to the fact that L-tyrosine is converted into catecholamines, synthesizing stimulatory neurotransmitters. In certain individuals, this increased CNS stimulation can result in heart rate abnormalities.
Agitation: Some people become increasingly agitated when they first start taking L-tyrosine. This may be due to the time of day in which it is taken, but could also be related to the dosage. To decrease the likelihood of agitation, L-tyrosine should only be taken intermittently on an “as-needed” basis at a low dose.
Anxiety: While some people experience a counterintuitive decrease in anxiety from L-tyrosine, most people experience a mild increase. The increase in anxiety may result from increased catecholamine synthesis, promoting increased vigilance and heightened stimulation. If anxiety becomes severe, decreasing the dosage and/or discontinuation may be advised.
Appetite changes: Some people notice that their appetite decreases when taking L-tyrosine. This decrease in appetite could be temporary and fueled by an increase in synthesis of catecholamines. If catecholamine levels are suboptimal, L-tyrosine supplementation may increase their levels within a normal range, inducing a temporary reduction of appetite.
Blood pressure changes: Scientific research suggests that L-tyrosine is capable of increasing and/or decreasing blood pressure – based on the individual. Those with hypertension should be monitored for spikes in blood pressure following administration of L-tyrosine. While L-tyrosine is more likely to increase blood pressure, it may decrease blood pressure in select individuals.
Chest pain: It has been reported that chest pain may occur when taking L-tyrosine. The chest pain experienced is generally mild and accompanied by shortness of breath and/or heart rate abnormalities. It is important to realize that chest pain could be a sign of a serious adverse effect. Consult a medical professional if L-tyrosine supplementation provokes chest pain.
Diarrhea: At higher doses of L-tyrosine, people are at increased risk of experiencing disaster pants a.k.a. diarrhea. Lower doses may cause an upset stomach, or gastrointestinal discomfort, but at higher doses, you may experience an unwanted excess of bowel movements. This side effect can often be mitigated by reducing the dosage and/or temporary discontinuation.
Difficulty breathing: You may notice that you experience breathing difficulties following administration of L-tyrosine. These breathing difficulties may be triggered by increases in CNS stimulation associated with synthesis of stimulatory neurotransmitters. Should you experience changes in respiratory function, seek immediate medical attention.
Dizziness: Many people report increases in dizziness when they first start taking L-tyrosine. The dizziness is generally mild or moderate, but may be more extreme among those ingesting high doses of L-tyrosine. Dizziness generally subsides as the body adapts to the presence of L-tyrosine, but may also diminish with a dosage reduction.
Drowsiness: A counterintuitive reaction from L-tyrosine supplementation is drowsiness. Should you become drowsy, it is important to consider potential interaction effects and/or that your body may not respond well to L-tyrosine supplementation. Drowsiness may diminish after a week of consistent supplementation and/or with reductions in dosing.
Fatigue: A side effect that some people experience while taking L-tyrosine is increased fatigue. The increase in fatigue is generally not extreme to the extent of sleepiness, but may be pronounced. This is considered a counterintuitive reaction due to the fact that L-tyrosine is associated with increases in vigilance and energy. Some people find that fatigue decreases as the body adapts to L-tyrosine, while others find altering the dosage helpful.
Headaches: One of the most common side effects from L-tyrosine supplementation is a headache. Most people experience mild or moderate headaches, which may be caused by increased synthesis of stimulatory neurotransmitters. Should headaches become severe, it is important to consider reducing the dosage. Further, realize that interactions and/or dehydration may exacerbate L-tyrosine-induced headaches.
Heartburn: In some cases, a person may experience indigestion accompanied by burning sensations in their chest when taking L-tyrosine. This is related to regurgitation of stomach acid back into the esophagus. If you notice that this supplement is triggering heartburn, discontinue and/or lower the dosage and determine whether the heartburn subsides.
Heart palpitations: If you notice that your heart becomes increasingly strong, rapid, or irregular after L-tyrosine supplementation, it may not be a coincidence. Increases in concentrations of stimulatory neurotransmitters and heightened arousal could promote heart palpitations. These palpitations may be uncomfortable and lead to increases in anxiety.
Insomnia: L-tyrosine is capable of triggering insomnia, or inability to fall asleep. Others may find that L-tyrosine increases the likelihood of broken sleep and decreases sleep quality. By reducing the dosage and taking L-tyrosine in the morning (rather than afternoon or night), insomnia may be less likely to occur.
Irritability: It is known that L-tyrosine can increase catecholamine synthesis, which in turn can increase CNS activation (arousal), and provoke feelings of irritability. Those that experience irritability from L-tyrosine may be more prone to agitation, restlessness, and nervousness. In some cases, the irritability diminishes as the neurophysiology adapts to supplementation.
Joint pain: A relatively odd side effect associated with L-tyrosine supplementation is joint pain. The joint pain associated with supplementation of L-tyrosine is generally mild, but may be exacerbated by increased doses. To reduce the likelihood of joint pain, consider lowering your dosage and/or temporary discontinuation.
Nausea: Another unfavorable side effect associated with L-tyrosine is that of nausea. The nausea associated with L-tyrosine is generally mild, but may become increasingly severe with higher doses. Some individuals have reported that the nausea from L-tyrosine supplementation became so extreme that they nearly vomited.
Nervousness: As a result of increased catecholamine production, many people find L-tyrosine causes nervousness. This heightened nervousness is generally mild or moderate, but may be troubling for individuals with a history of anxiety. Nervousness may subside as the body adjusts to accommodate increases in catecholamine reserves, but not in all cases.
Restlessness: Since L-tyrosine facilitates the production of dopamine, norepinephrine, and epinephrine – increased CNS stimulation is oftennoted. This increase in CNS stimulation may elicit feelings of restlessness. A person may feel unsettled, nervous, and have a difficult time sitting still with an increased need to move around or pace.
Skin rashes: Certain individuals may be unable to tolerate L-tyrosine as evidenced by skin rashes. The rash may be concentrated in a specific area or widespread throughout the body. It may be itchy as a result of “hives” and characterized by swelling. Development of a rash may be related to dosage, interactions, source of L-tyrosine, or individual intolerability.
Stomach aches: It is known that higher doses of L-tyrosine can cause gastrointestinal discomfort, ultimately contributing to stomach aches and pains. Those that experience stomach aches may find that a dosage reduction lessens the severity of the aches. Most stomach aches experienced are mild, but may increase in severity with high doses.
Thyroid dysfunction: It is possible to end up with hyperthyroidism (overactive thyroid) from supplementing with L-tyrosine. This is due to the fact that L-tyrosine can stimulate the production of thyroid hormones. If you have a history of hyperthyroidism or are taking thyroid medications, it is important to avoid supplementation of L-tyrosine.
Weight loss: Some people end up losing weight when they first start taking L-tyrosine. There is some evidence to suggest that L-tyrosine can improve neurophysiological function associated with dietary restriction, ultimately provoking weight loss. In addition, some people find that L-tyrosine suppresses their appetite while simultaneously provides more energy to hit the gym.

L-Tyrosine: Weighing the Pros (Benefits) & Cons (Side Effects)

It is important to always weigh the therapeutic benefits with the side effects when taking any supplement, including L-tyrosine. Certain individuals may find that the therapeutic benefits for cognitive function significantly outweigh any side effects. For example, assuming you take L-tyrosine and your focus significantly improves without any side effects; in this case the benefits clearly outweigh the side effects (because you don’t have any).

Another individual may find that taking L-tyrosine triggers severe anxiety and heart palpitations. This person may not derive (or notice) any significant therapeutic benefit from L-tyrosine supplementation. In this case, it is relatively obvious that the side effects outweigh the benefits (because none were experienced).

It gets trickier to determine whether the benefits outweigh the side effects when a person experiences noticeable cognitive enhancement coupled with diarrhea and nausea. Ultimately it is up to you to assess whether the benefits are substantial enough to proceed with supplementation despite the disconcerting side effects. After a few weeks of supplementation and dosage tweaking, most people will be able to determine whether L-tyrosine is a good fit for their individual biochemistry.

Have you noticed any significant L-Tyrosine side effects?

If you’ve taken L-tyrosine, feel free to share a comment mentioning whether you’ve experienced any significant side effects and/or adverse reactions. To help others get a better understanding of your situation, mention the dosage you were taking, the time span over which you had been taking L-tyrosine, and the frequency of administration. Also provide more specifics such as the brand and formulation of L-tyrosine, whether you took it with other drugs (or supplements), and the time of day you took it.

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