What Is Serotonin?

A chemical that helps regulate mood

Serotonin is a chemical messenger (neurotransmitter) that helps brain and nervous system cells communicate. Its main function is to stabilize your mood, as well as your feelings of happiness and well-being. Serotonin also plays a role in the digestive system and sleep cycles.

The body needs serotonin, but too much or too little can lead to health issues. For example, too little serotonin can cause depression. Too much, however, can cause a rare condition called serotonin syndrome.

This article discusses the functions of serotonin and what can happen if your levels are off. It also looks at ways to naturally increase your body's serotonin levels.

What Does Serotonin Do?

Serotonin is produced in the brain. The body uses an amino acid called tryptophan hydroxylase to create it.

What does Serotonin do?

Verywell / Nez Riaz

Serotonin plays a key role in the central nervous system, which is composed of the brain and spinal cord). This system controls the majority of your body and mind functions.

Serotonin is responsible for mood regulation. It can reduce feelings of depression and anxiety and increase feelings of joy or happiness. It also plays a role in other aspects of your health, including:

  • Sleep: Serotonin stimulates parts of the brain that control sleep-wake behavior.
  • Bowel movements: Serotonin affects how well the bowel functions. It also plays a role in controlling bowel movements. Most of the body’s serotonin can be found in the digestive system.
  • Blood clotting: Blood platelets use serotonin to help your body heal wounds. Serotonin encourages the formation of blood clots and the narrowing of some tiny arteries.
  • Nausea: When you eat something that your stomach doesn't agree with, your body will make more serotonin. Increasing serotonin blood levels can trigger feelings of nausea.
  • Bone health: Osteoporosis causes bones to become weak or brittle. Studies have shown that this condition is associated with high levels of serotonin in the body. This means that overall bone health may depend on having the right serotonin levels.
  • Sex drive: Serotonin levels that are too high can cause a decrease in your libido. If your levels are too low, however, you may have a higher than usual libido.

Having too much or too little serotonin can cause problems with these functions.

Serotonin Deficiency

It is possible for your serotonin levels to be too low. Serotonin deficiency can be caused by:

  • Low tryptophan levels: If your body does not have enough of this amino acid, it cannot produce enough serotonin.
  • Specific nutrients: Research has shown that vitamin D and omega-3 fatty acids may modulate the creation, release, and function of serotonin. This is because tryptophan needs vitamin D to do its job. Omega-3s have also been shown to help brain dysfunction. This is because of their effect on serotonin production.
  • Not enough serotonin receptors: A serotonin receptor is a protein that handles serotonin signals. It is possible to have too few serotonin receptors or receptors that don’t work. This can lead to depression and an increased risk of suicide.
  • Stress: Studies have shown that high stress levels in childhood can lead to lower levels of serotonin as an adult.

How Low Levels Affect the Body

Serotonin affects many body processes. For this reason, inadequate amounts can lead to both psychological and physiological issues. Some symptoms and conditions associated with serotonin deficiency can be grouped into these categories:

  • Psychological: People with low serotonin may experience aggression, poor impulse control, insomnia, irritability, and low self-esteem. Psychological conditions related to low serotonin include anxiety and panic disorder, depression, eating disorders, and obsessive-compulsive disorder (OCD).
  • Cognitive: Low serotonin is associated with cognitive symptoms like poor memory.
  • Physiological: Some physiological symptoms may include craving carbohydrates, unintentional weight gain, nausea, digestive issues, poor appetite, and fatigue.

Low serotonin levels have also been associated with certain chronic diseases. This includes Alzheimer’s disease and Parkinson’s disease.

When Serotonin Is Too High

Most of the time, dangerously high serotonin is caused by drugs that increase serotonin activity. In rare cases, it's can be caused by a tumor.

Excessive serotonin levels can be life-threatening.

Serotonin Syndrome

Serotonin syndrome occurs when serotonin levels in the body become too high. It can be life-threatening and requires emergency medical care.

Serotonin syndrome doesn't usually occur naturally. Common causes of serotonin syndrome include:

  • Medications that increase serotonin levels, such as selective serotonin reuptake inhibitors (SSRIs), a type of antidepressant
  • Certain pain medications such as Demerol (meperidine) 
  • Over-the-counter cold medicines and cough suppressants containing dextromethorphan
  • Migraine medications, such as triptans
  • Medications used to treat human immunodeficiency virus (HIV)
  • Anti-nausea medications like Reglan (metoclopramide) and Zofran (ondansetron)
  • Supplements, including ginseng and Saint John's Wort
  • Illicit drugs like ecstasy, cocaine, or LSD

Symptoms of serotonin syndrome can be mild or severe. Mild symptoms may include:

  • Nervousness
  • Insomnia
  • Nausea
  • Diarrhea
  • Tremors
  • Dilated pupils

Moderate symptoms can include:

  • Hyperactive reflexes
  • Sweating
  • Agitation and restlessness
  • Involuntary muscle contractions
  • Side-to-side eye movements

In severe cases, serotonin syndrome can cause:

  • High fever
  • Confusion or delirium
  • Sustained involuntary muscle contractions
  • Rhabdomyolysis, or the breaking down of damaged muscle

Without immediate treatment, serotonin syndrome can lead to unconsciousness and death.

If you have any of the above symptoms and have recently started or increased your dose of a medication that can affect serotonin levels, seek medical care right away.

Carcinoid Syndrome

A condition called carcinoid syndrome can cause high serotonin levels in the blood. This syndrome is caused by a tumor that produces too much serotonin. Symptoms can include:

  • Flushed skin or redness
  • Facial skin lesions
  • Gastrointestinal issues, such as frequent diarrhea and abdominal cramps
  • Asthma-like symptoms, such as wheezing
  • Rapid heartbeat
  • Dehydration
  • Weakness
  • Muscle and joint pain

Regulating Serotonin

It is possible to boost low serotonin with supplements or lifestyle changes like diet and exercise. High serotonin, however, requires immediate medical treatment.

Treating Low Serotonin

Medications can help treat low serotonin. These include SSRIs, which help the body make better use of serotonin. These drugs are often prescribed if you have symptoms of depression. Depending on the length and severity of your symptoms, you may need to take SSRIs long term.

Certain dietary supplements can also help restore normal serotonin levels, including:

  • S-adenosylmethionine (SAMe): This is the supplement version of a compound found naturally in the body. SAMe may help your body synthesize serotonin and other important neurotransmitters.
  • 5-HTP: This is the supplement version of a natural amino acid found in your body.
  • Probiotics: Studies have shown that probiotics ("good bacteria") may help increase tryptophan levels in the blood.

It is important to remember that some supplements, especially when combined with drugs that affect serotonin levels, may put you at risk for developing serotonin syndrome. Always ask a healthcare provider before starting a new supplement.

There are also natural ways to boost your serotonin levels. You may need to do these things regularly in order to keep your serotonin levels high:

  • Increasing tryptophan: Tryptophan is a basic building block of serotonin. If your serotonin levels are low, you may be able to help boost them by eating foods high in this amino acid. Some examples include eggs, tofu, salmon, turkey, nuts and seeds, and cheese. Studies have also shown that eating more carbs along with foods high in tryptophan may help tryptophan reach the brain.
  • Light exposure: Light therapy can improve serotonin levels and decrease symptoms of depression. The light can be from the sun or a lightbox. Research has shown that exposure to sunlight may help the body synthesize serotonin through the skin.
  • Exercise: Getting enough exercise is important for overall health. It can also boost serotonin levels naturally. Exercise triggers the release of tryptophan into the blood, which drives serotonin production. Aerobic exercise, like swimming, biking, or running, is particularly helpful in this regard.
  • Massage: Massage therapy has been shown to help increase serotonin. It can also decrease levels of cortisol, which is sometimes called the stress hormone.
  • Meditation: Research has also found that meditation can help boost serotonin in the brain.

Treating High Serotonin

People with serotonin syndrome are typically hospitalized for a minimum of 24 hours.

Mild cases caused by medication can usually be resolved by stopping the medication or changing the dose.

Healthcare providers may also prescribe medications that can stop the body from producing serotonin, help relieve symptoms, and keep the condition from worsening. Medications that may be used in the hospital include: 

  • Benzodiazepines: These are used to help decrease agitation, seizure-like movements of the body, and muscle stiffness. 
  • Periactin (cyproheptadine): This medication blocks the production of serotonin.

Longer hospital stays may be required in severe cases, in which patients need close monitoring for changing or worsening symptoms.

Patients may need medications that paralyze their muscles. Some may also need to be temporarily put on a breathing machine to prevent muscle damage. 


Serotonin is a neurotransmitter. It plays an important role in regulating mood, sleep, and your digestive system.

High or low levels of serotonin can lead to health problems. High levels of serotonin can cause serotonin syndrome, a life-threatening condition. Low levels can cause depression. Both high and low serotonin can be treated with medication. There are also natural ways to boost low serotonin levels.

Frequently Asked Questions

  • How common is serotonin syndrome?

    The prevalence of serotonin syndrome isn't known. One small study found that roughly 7.8% of 309 intensive care unit (ICU) patients had some symptoms of serotonin syndrome. It's important to note, though, that this is not a typical patient population.

  • When is serotonin released?

    The release of serotonin can happen at different times of the day during different activities. It is also produced when you eat something that makes you nauseous. Massage therapy, spending time in sunlight, and exercising have also been shown to trigger the release of serotonin.

  • How long does it take for serotonin to replenish?

    There is no set time for how long it takes to replenish serotonin. This is because brain chemistry varies from person to person. For mild cases of serotonin deficiency, levels may be replenished quickly. In other cases, it may take longer.

27 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Endocrine Society. What is serotonin?

  2. Strasser B, Gostner JM, Fuchs D. Mood, food, and cognition: role of tryptophan and serotonin. Curr Opin Clin Nutr Metab Care. 2016;19(1):55-61. doi:10.1097/MCO.0000000000000237

  3. Cowen PJ, Browning M. What has serotonin to do with depression? World Psychiatry. 2015;14(2):158-160. doi:10.1002/wps.20229

  4. Monti JM. Serotonin control of sleep-wake behavior. Sleep Med Rev. 2011;15(4):269-281. doi:10.1016/j.smrv.2010.11.003

  5. Vahora IS, Tsouklidis N, Kumar R, Soni R, Khan S. How serotonin level fluctuation affects the effectiveness of treatment in irritable bowel syndrome. Cureus. 2020;12(8):e9871. doi:10.7759/cureus.9871

  6. de Vernejoul MC, Collet C, Chabbi-Achengli Y. Serotonin: good or bad for bone. Bonekey Rep. 2012;1:120. doi:10.1038/bonekey.2012.120

  7. Croft HA. Understanding the role of serotonin in female hypoactive sexual desire disorder and treatment options. J Sex Med. 2017;14(12):1575-1584. doi:10.1016/j.jsxm.2017.10.068

  8. Jenkins TA, Nguyen JC, Polglaze KE, Bertrand PP. Influence of tryptophan and serotonin on mood and cognition with a possible role of the gut-brain axis. Nutrients. 2016;8(1):56. doi:10.3390/nu8010056

  9. Patrick RP, Ames BN. Vitamin D and the omega-3 fatty acids control serotonin synthesis and action, part 2: relevance for ADHD, bipolar disorder, schizophrenia, and impulsive behavior. FASEB J. 2015;29(6):2207-2222. doi:10.1096/fj.14-268342

  10. Underwood MD, Kassir SA, Bakalian MJ, et al. Serotonin receptors and suicide, major depression, alcohol use disorder and reported early life adversity. Transl Psychiatry. 2018;8(1):279. doi:10.1038/s41398-018-0309-1

  11. De Bellis MD, Zisk A. The biological effects of childhood trauma. Child Adolesc Psychiatr Clin N Am. 2014;23(2):185-222, vii. doi:10.1016/j.chc.2014.01.002

  12. Byers AL, Yaffe K. Depression and risk of developing dementia. Nat Rev Neurol. 2011;7(6):323-331. doi:10.1038/nrneurol.2011.60

  13. Weng R, Shen S, Tian Y, et al. Metabolomics approach reveals integrated metabolic network associated with serotonin deficiency. Sci Rep. 2015;5:11864. doi:10.1038/srep11864

  14. National Library of Medicine. Serotonin syndrome.

  15. Volpi-Abadie J, Kaye AM, Kaye AD. Serotonin syndrome. Ochsner Journal. 2013;13(4):533-40.

  16. Foong AL, Patel T, Kellar J, Grindrod KA. The scoop on serotonin syndrome. Can Pharm J (Ott). 2018;151(4):233-239. doi:10.1177/1715163518779096

  17. National Organization for Rare Disorders. Carcinoid syndrome.

  18. Cartwright C, Gibson K, Read J, Cowan O, Dehar T. Long-term antidepressant use: patient perspectives of benefits and adverse effectsPatient Prefer Adherence. 2016;10:1401-1407. doi:10.2147/PPA.S110632

  19. Levkovitz Y, Alpert JE, Brintz CE, Mischoulon D, Papakostas GI. Effects of S-adenosylmethionine augmentation of serotonin-reuptake inhibitor antidepressants on cognitive symptoms of major depressive disorder. Eur Psychiatry. 2012;27(7):518-21.

  20. Wallace CJK, Milev R. The effects of probiotics on depressive symptoms in humans: a systematic review. Ann Gen Psychiatry. 2017;16:14. doi:10.1186/s12991-017-0138-2

  21. Fernstrom JD. Effects and side effects associated with the non-nutritional use of tryptophan by humans. J Nutr. 2012;142(12):2236S-44S. doi:10.3945/jn.111.157065

  22. Singh K. Nutrient and stress management. J Nutr Food Sci. 2016;6(4):1-6. doi:10.4172/2155-9600.1000528

  23. Sansone RA, Sansone LA. Sunshine, serotonin, and skin: a partial explanation for seasonal patterns in psychopathology? Innov Clin Neurosci. 2013;10(7-8):20-4.

  24. Heijnen S, Hommel B, Kibele A, Colzato LS. Neuromodulation of aerobic exercise-a review. Front Psychol. 2016;6:1890. doi:10.3389/fpsyg.2015.01890

  25. Field T. Massage therapy research review. Complement Ther Clin Pract. 2014;20(4):224-229. doi:10.1016/j.ctcp.2014.07.002

  26. Krishnakumar D, Hamblin MR, Lakshmanan S. Meditation and yoga can modulate brain mechanisms that affect behavior and anxiety-a modern scientific perspective. Anc Sci. 2015;2(1):13-19. doi:10.14259/as.v2i1.171

  27. Prakash S, Rathore C, Rana K. The prevalence of serotonin syndrome in an intensive care unit: a prospective observational study. J Crit Care. 2021;63:92-97. doi:10.1016/j.jcrc.2020.12.014

By Angelica Bottaro
Angelica Bottaro is a professional freelance writer with over 5 years of experience. She has been educated in both psychology and journalism, and her dual education has given her the research and writing skills needed to deliver sound and engaging content in the health space.