A Closer Look at Serotonin and What It Does in the Body

Medically Reviewed By Debra Sullivan, Ph.D., MSN, R.N., CNE, COI
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Serotonin is a neurotransmitter and hormone that plays a key role throughout your body. Serotonin levels affect functions including your moods, memory, sex drive, sleep patterns, gut function, bone health, and blood clotting. Serotonin, also called 5-hydroxytryptamine (5-HT), forms in the lining of your gastrointestinal (GI) tract and within your brain. It carries messages between nerve cells in your body and governs many psychological and biological processes.

This article will look at the role of serotonin in your body and brain. It will also discuss serotonin deficiency and how you can raise the levels of serotonin in your body.

What is serotonin?

The raw material for serotonin is the essential amino acid tryptophan. This is found in foods such as nuts, cheese, and red meat.

Enzymes and amino acids in your body act on tryptophan to produce serotonin. Research shows that 95% of serotonin production occurs in the lining of your GI tract. Your brain produces the remaining 5%. Serotonin influences numerous processes both in your gut and in your brain.

What is the function of serotonin in the body and the brain?

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Researchers have studied how serotonin plays a role in the central nervous system (CNS) and influences mood, anxiety, memory, and depression. Some recent studies show how serotonin also affects many, if not all, biological processes in the body.

Serotonin’s role throughout the body

  • In the mind: Serotonin plays a role in many mental functions such as decision making and feelings of happiness. Serotonin’s role in mood regulation could mean that low serotonin levels affect depression and anxiety.
  • In the gut: Enterochromaffin cells (EC) release serotonin in the digestive tract. This helps maintain healthy gut function, and serotonin levels can affect symptoms such as nausea and vomiting. Altered serotonin levels may lead to functional bowel disorders, including irritable bowel syndrome (IBS).
  • Immune cell function: Serotonin exists in almost all immune cells. It helps to regulate your immune response and plays a part in inflammation.
  • Blood clotting: Blood platelets release serotonin to help heal wounds.
  • Bone growth: Serotonin plays a role in bone growth.
  • Heart function: Serotonin regulates different aspects of cardiac function, including electrical conduction and valve function.
  • Breathing: Serotonin helps control breathing by affecting the respiratory control centers in the brain stem.
  • Sleep: Serotonin affects your sleep by stimulating the parts of the brain that control sleep and wakefulness. Serotonin also plays a role in the production of melatonin, a hormone that is vital for sleep.
  • Sexual function: Researchers have linked low levels of serotonin to an increased libido. Additionally, they have linked increased serotonin levels to reduced libido.

The gut-brain axis

Interesting research shows that serotonin levels in the body and in the brain actually influence each other. The communication line between your CNS and your intestinal system is called the gut-brain axis (GBA).

The GBA brings the two systems together, linking the emotional and cognitive centers of the brain to intestinal function. Recent advances in research show that your gut microbiome can affect your moods and vice versa.

Learn more about the gut-brain connection here.

What is the standard range for serotonin levels?

Doctors measure serotonin levels in the blood with a simple blood test. Typical serotonin blood levels range between 101–283 nanograms per milliliter.

Serotonin levels in the brain cannot be measured. There is no evidence that the level of serotonin in your blood reflects the level of serotonin in your brain.

As a result, researchers are not exactly sure what the right levels are and how these levels might vary for different people.

What is serotonin deficiency?

Serotonin deficiency can happen when your body does not produce enough serotonin, or if your body is not using serotonin efficiently.

  • Low production: Low levels of vitamin B6 and vitamin D are both linked to decreased levels of serotonin. In addition, you can only obtain tryptophan — an amino acid that is the raw material for serotonin production — through your diet.
  • Inefficient usage: Your body may not be able to use available serotonin efficiently due to a lack of sufficient receptors in your brain. Similar problems can occur when the existing receptors reabsorb the serotonin too quickly.

Symptoms of low serotonin

Researchers have linked decreased levels of serotonin to symptoms that include:

  • depressed mood
  • low self-esteem
  • problems with memory
  • insomnia or other sleep issues
  • increased sex drive
  • craving sweet foods

If you are experiencing these symptoms or other symptoms of anxiety and depression, talk with your doctor or mental health professional. They can provide further evaluation and discuss possible treatment options with you.

How does serotonin affect mental health?

Because serotonin plays such a significant role in mental health, one primary treatment for depression is a type of medication called selective serotonin reuptake inhibitors (SSRIs). These work by slowing down the rate at which serotonin is reabsorbed into the body. This slower uptake keeps your serotonin levels elevated.

Examples of SSRIs include:

However, a 2016 study in the journal Nutrients shows that low levels of serotonin do contribute to a lower mood state, but the low level must be accompanied by a biological or genetic problem that causes a an interaction with the low serotonin levels. The same study finds that antidepressants were only 48% effective in treating moderate to severe depression. These findings suggest that other systems also affect depression and that the complexity of the serotonin system requires further research.

Learn more about 12 drugs doctors commonly prescribe to treat depression.

What is serotonin syndrome?

Serotonin syndrome is a potentially life threatening condition that can result when taking serotonin drugs, which could lead to too much serotonin in your system. It can happen when you start taking a new medication or increase the dosage of an existing medication. It can also happen when medications interact or when someone uses recreational drugs that cause a surge in serotonin.

Symptoms of serotonin syndrome can range from mild to severe and include:

Treatment for serotonin syndrome

Treatment includes immediately stopping the medications that may have led to serotonin syndrome. Healthcare teams may also administer hydration and provide supportive care to manage blood pressure and respiratory and cardiac complications. In some cases, people may receive sedation.

What are tips for boosting serotonin levels?

Research shows that you may be able to boost your levels of serotonin naturally through certain lifestyle habits, including diet and exercise.


The 2016 Nutrients study found that a diet low in tryptophan can decrease serotonin levels in the brain. However, researchers are unclear about the effect of eating high-tryptophan foods on raising the brain’s serotonin levels.

  • High in tryptophan: Foods that are high in tryptophan include meats, dairy, fruits, and seeds.
  • Complex carbohydrates: Research shows that a diet rich in complex carbohydrates such as whole grains, vegetables, and fruits, can boost the levels of serotonin in your body. The fiber in these foods can also slow digestion, which keeps serotonin levels steady.
  • Probiotics: The gut-brain axis refers to the two-way communication network between your GI tract and your CNS. A diet that is rich in probiotics can encourage helpful bacteria in your gut to flourish, which in turn may raise serotonin levels and improve mood.


Regular exercise can help raise your levels of serotonin by releasing tryptophan into your blood. Aim for aerobic exercises such as swimming, jogging, biking, skipping, cycling, and walking.


Research shows that mood and anxiety disorders can worsen when people are not exposed to sunlight or other bright light. Scientists believe there is a link between sunlight, serotonin, and good moods.


Massage therapy helps to increase levels of serotonin and dopamine. Massages also help to decrease cortisol, which is a stress hormone.

Frequently asked questions

Other questions people often ask about serotonin include:

Do bananas increase serotonin?

Some research shows that fruits can help to raise levels of serotonin by providing fiber that remains in your GI tract for longer. It also encourages the secretion of serotonin.

Does coffee increase serotonin?

Research shows that caffeine can improve mood quickly by stimulating dopamine and serotonin. However, over time, caffeine depletes serotonin, which will leave you feeling down.

Can I buy serotonin?

You cannot buy serotonin, but you can buy tryptophan. It is possible that your body could use tryptophan to synthesize serotonin, but more research needs to be done in this area. Always talk with your doctor before starting any supplement.

What time of day is serotonin the highest?

In studies of rats, results differed in terms of when serotonin levels were highest. A 2009 study measures the highest serotonin levels at nightfall. An earlier study in 2007 cites research that found the opposite: Rats had the highest levels during daylight hours. The 2007 research notes that, in humans, bright light led to higher levels of serotonin.


Serotonin is a chemical that plays a role in both your physical and mental functions. The production of most of the serotonin in your body occurs in the gut, with the remaining produced in the brain.

Research has linked low serotonin levels to anxiety and depression. Symptoms of serotonin deficiency include low mood, memory problems, and sleep issues. For this reason, treatment for depression often includes medications called SSRIs.

Talk with your doctor or mental health professional if you experience symptoms of low serotonin or other symptoms of depression or anxiety. They can evaluate your symptoms and discuss available treatment options to restore standard serotonin levels.

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Medical Reviewer: Debra Sullivan, Ph.D., MSN, R.N., CNE, COI
Last Review Date: 2022 Apr 25
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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