5-hydroxytryptophan (5-HTP) is the precursor to the neurotransmitter serotonin. This neurotransmitter plays a role in many important bodily functions, including mood regulation.

5-HTP is available as a supplement. Some older research suggests that it may help with mood issues, such as depression and anxiety, as well as headaches, chronic pain, and insomnia.

In this article, we describe what 5-HTP is and how it works. We also discuss the potential side effects of 5-HTP supplements.

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Neurotransmitters are chemicals that help carry nerve signals between neurons. Serotonin is a neurotransmitter that plays an important role in numerous bodily functions, including:

  • mood regulation
  • sleep
  • pain perception
  • digestion
  • blood clotting

To make serotonin, the body needs an amino acid called tryptophan. The human body cannot make tryptophan, so a person must get it from the food they eat. Once the body receives tryptophan, it converts it to 5-HTP. It then converts the 5-HTP into serotonin.

5-HTP supplements are also available. Learn more here.

Without tryptophan, the body cannot make serotonin. The National Capital Poison Center note that tryptophan was available in the form of supplements until the Food and Drug Administration (FDA) banned them in 1989. The ban came into place after a contaminated batch of tryptophan caused the deaths of at least 30 individuals and made more than 1,500 people very sick.

As 5-HTP is a precursor to serotonin, it is a suitable alternative to tryptophan supplements. 5-HTP supplements may help raise serotonin levels, especially in people who do not get enough tryptophan from their diets and those whose body does not make enough serotonin.

Research suggests that 5-HTP is highly absorbable. An older review from 1998 notes that the body absorbs about 70% of an oral 5-HTP supplement into the bloodstream.

The potential risks and side effects of 5-HTP vary among children, adults, and people who are pregnant or breastfeeding.

In children

5-HTP is not safe for children.

In adults

The possible side effects of 5-HTP in adults include:

Serotonin syndrome

Serotonin syndrome is a life threatening emergency that happens when a person has dangerously high levels of serotonin in their brain. Symptoms of serotonin syndrome may include:

Serotonin syndrome usually occurs as a result of taking multiple serotonin-producing drugs. For example, a person may develop the condition after taking a selective serotonin reuptake inhibitor (SSRI) or a serotonin and norepinephrine reuptake inhibitor (SNRI) with one of the following:

Due to this risk, people who take antidepressants or other serotonin drugs should not take 5-HTP.

Changes in levels of other neurotransmitters

Long-term use of 5-HTP may deplete levels of a group of neurotransmitters called catecholamines. This group includes:

Catecholamine depletion can affect mood and bodily functions, and it may also stop 5-HTP from working.

Gastrointestinal issues

Some people report the following gastrointestinal (GI) symptoms after taking 5-HTP:

  • heartburn
  • gas
  • rumbling sensations in the stomach
  • feelings of uncomfortable fullness

Heart and blood vessel issues

Serotonin causes tiny blood vessels to narrow, which helps promote blood clotting. This narrowing can, therefore, help stop bleeding after an injury, but it may increase the risk of dangerous blood clots in some people.

People with a history of high blood pressure or other cardiovascular risk factors should talk to a doctor before taking 5-HTP.


Very high levels of serotonin in the blood may lead to osteoporosis, in which the bones weaken, especially in people with other risk factors for the condition.

People with osteoporosis often do not experience any symptoms. The first sign is usually a broken bone following a minor fall or another injury.

A person who already has a diagnosis of osteoporosis should talk to their doctor before considering taking 5-HTP.

Eosinophilia-myalgia syndrome

Eosinophilia-myalgia syndrome (EMS) is a rare disease that causes elevated levels of white blood cells called eosinophils in the body’s tissues. These raised levels can lead to the following symptoms:

Severe cases of EMS can lead to multiple organ failure and death. EMS is the syndrome that led to the deaths of people who took tryptophan supplements in 1989.

A few people who have taken 5-HTP have since reported symptoms of EMS.

Overdose and toxicity

Higher doses of 5-HTP increase the risk of serious side effects, including overdose and organ failure.

The FDA do not regulate supplements, meaning that there may be significant differences in content and quality among batches and brands. This inconsistency increases the risk of overdose and poisoning.

Allergic reaction

As with any supplement, it is possible to have an allergic reaction to 5-HTP. Severe allergic reactions are possible but rare.

Anyone who experiences symptoms of a severe allergic reaction, or anaphylaxis, after taking 5-HTP should seek emergency medical attention. These symptoms may include:

  • skin rash or hives
  • swelling of the lips, tongue, or throat
  • shortness of breath, or difficulty breathing
  • stomach pain
  • abdominal cramps
  • vomiting or diarrhea
  • a feeling of impending doom

During pregnancy and breastfeeding

Scientists have not sufficiently evaluated the safety of using 5-HTP when pregnant or breastfeeding. As a result, these individuals should avoid taking this supplement.

5-HTP may interact with any drug that increases serotonin, including:

People who take any of the above drugs should not take 5-HTP. Doing so can potentially cause serotonin syndrome.

As a general rule, people should always consult a doctor before taking a supplement for the first time.

There is no FDA-approved dosage of 5-HTP. An overdose can be lethal, so it is important to begin with a small dose and to avoid taking more than the product label recommends.

A person should talk to their doctor before taking a new supplement. Some supplements can worsen existing health conditions or interact with other medications. A doctor may also be able to advise on an appropriate supplement dosage.

After taking 5-HTP, a person should call a doctor if:

  • the 5-HTP does not improve their symptoms
  • they develop new or worsening symptoms while taking 5-HTP
  • they experience unpleasant side effects

A person will need emergency medical attention if anaphylaxis or signs of serotonin syndrome occur after taking 5-HTP.

5-HTP is a supplement that may help boost levels of the neurotransmitter serotonin. Some older research suggests that it may help regulate mood and alleviate headaches, chronic pain, and insomnia. However, further research is necessary to support these claims.

5-HTP may cause side effects in some people. Possible severe side effects include serotonin syndrome and anaphylaxis. Anyone who experiences symptoms of these side effects should seek emergency medical attention.

A person should talk with their doctor before taking 5-HTP or any other supplements. Some supplements can worsen underlying medical conditions or interact with medications that a person is already taking.