Serotonin: Functions, normal range, side effects, and more Health ConditionsHealth ConditionsAlzheimer's & DementiaAnxietyArthritisAsthma & AllergiesBreast CancerCancerCardiovascular HealthCOVID-19Dermatology & SkincareDiabetesEnvironment & SustainabilityExercise & FitnessEye HealthHeadache & MigraineHealth EquityHIV & AIDSHuman BiologyInflammatory Bowel DiseaseLeukemiaLGBTQIA+Men's HealthMental HealthMultiple Sclerosis (MS)NutritionParkinson's DiseasePsoriasisSexual HealthWomen's HealthDiscoverNewsLatest NewsOriginal SeriesMedical MythsHonest NutritionThrough My EyesNew Normal HealthPodcastsHow to understand chronic painWhat is behind vaccine hesitancy?The amazing story of hepatitis C, from discovery to cureNew directions in dementia researchCan psychedelics rewire a depressed, anxious brain?Why climate change matters for human healthToolsGeneral HealthDrugs A-ZHealth HubsHealth ToolsBMI Calculators and ChartsBlood Pressure Chart: Ranges and GuideBreast Cancer: Self-Examination GuideSleep CalculatorHealth ProductsAffordable Therapy OptionsBlood Pressure MonitorsDiabetic SuppliesFitness TrackersHome GymsGreen Cleaning ProductsHow to Shop for CBDQuizzesRA Myths vs FactsType 2 Diabetes: Managing Blood SugarAnkylosing Spondylitis Pain: Fact or FictionConnectAbout Medical News TodayWho We AreOur Editorial ProcessContent IntegrityConscious LanguageNewslettersSign UpFollow UsMedical News TodayHealth ConditionsDiscoverToolsConnectSubscribe What is serotonin and what does it do Medically reviewed by William C Lloyd III, MD, FACS — By James McIntosh — Updated on October 4, 2022Serotonin has a wide variety of functions in the human body. People sometimes call it the “happy” chemical because it contributes to well-being and happiness. The scientific name for serotonin is 5-hydroxytryptamine (5-HT). It is a natural chemical mainly present in the brain, bowels, and blood platelets. Serotonin is a neurotransmitter, and some also consider it a hormone. The body uses it to send messages between nerve cells. Serotonin appears to affect mood, emotions, appetite, and digestion. As the precursor for melatonin, it helps regulate sleep-wake cycles and the body clock. Many investigations have looked at serotonin and its effects, but there is much to learn. In this article, we look at the role of serotonin in the body, drugs that affect serotonin, side effects and symptoms of serotonin deficiency, and how to boost serotonin levels. What is serotonin Share on PinterestImage credit: Klaus Vedfelt/Getty Images.Serotonin results from tryptophan, a component of proteins, combining with tryptophan hydroxylase, a chemical reactor. Together, they form 5-HT, or serotonin. The intestines and the brain produce serotonin. It is also present in blood platelets and plays a role in the central nervous system (CNS). Serotonin occurs throughout the body and appears to influence a range of physical and psychological functions. The substance is also present in animals, plants, and fungi. For this reason, some people have looked at food as a possible source of serotonin. However, serotonin cannot cross the blood-brain barrier. This means that the brain must produce any serotonin it needs. Treatments for depression and other mental health issues do not supply serotonin directly but trigger reactions that can boost serotonin levels in the brain. That said, research suggests that sources of serotonin in other areas, such as the digestive system, may work independently of serotonin in the brain. This could have implications for treating and preventing various physiological conditions, such as bone degeneration. Function As a neurotransmitter, serotonin relays signals between nerve cells and regulates their intensity. Scientists believe it plays a role in mood and the CNS and affects functions throughout the body. It may have an effect on: bone metabolismcardiovascular healtheye healthblood clottingneurological disorders However, the relationship between serotonin and many bodily functions remains unclear. Serotonin and mental health Scientists do not precisely know what causes depression, but one theory is that it stems from an imbalance of neurotransmitters in the body. Doctors commonly prescribe selective serotonin reuptake inhibitors (SSRIs) as antidepressants. Fluoxetine (Prozac) is one example. Typically, the body reabsorbs a neurotransmitter after transmitting its neural impulse. SSRIs stop the body from reabsorbing serotonin, leaving higher serotonin levels to circulate. Many people find SSRIs help relieve their symptoms, although the link between depression and serotonin remains unclear. One problem for researchers is that, while they can measure serotonin levels in the bloodstream, they cannot measure its levels in the brain. As a result, they do not know whether serotonin levels in the bloodstream reflect those in the brain. It is also impossible to know whether SSRIs can affect the brain. Nevertheless, while scientists have not yet proven the serotonin theory of depression, SSRIs do appear to help many people. Other disorders Apart from depression, doctors may prescribe drugs that regulate serotonin levels to treat several other disorders, including:bipolar disorderpost-traumatic stress disorderbulimiaobsessive-compulsive disorderpanic disordersmigraine As with depression, some scientists have questioned whether serotonin is the only factor affecting these conditions. Learn more about how to stop a panic attack. Typical ranges Medical professionals can measure a person’s serotonin blood levels but cannot measure serotonin levels in the brain. Typically, treatments aim to stabilize serotonin levels between 101 and 283 nanograms per milliliter. Serotonin deficiency symptoms According to the National Institute on Drug Abuse (NIDA), low serotonin levels can lead to memory problems and a low mood. These are symptoms of depression, although scientists have not confirmed a link between low serotonin levels and depression. NIDA notes that when people use certain recreational drugs, such as MDMA (ecstasy), the body releases large amounts of serotonin. This can lead to serotonin depletion, low mood, confusion, and other symptoms lasting several days. Animal studies have suggested that these drugs may damage the nerves that contain serotonin, with possible long lasting adverse effects. Learn more about serotonin deficiency. How to boost serotonin levels Medications, foods, and other natural remedies can alter serotonin levels. SSRIs increase serotonin levels by preventing the body from reabsorbing serotonin neurotransmitters. Serotonin levels remain high in the brain, and this may elevate a person’s mood. SSRIs that have approval from the Food and Drug Administration (FDA) for treating depression include:citalopram (Celexa)escitalopram (Lexapro)Prozacparoxetine (Paxil, Pexeva)sertraline (Zoloft)vilazodone (Viibryd) Learn more about SSRIs and other antidepressants. Adverse effects of SSRIs SSRIs have some side effects, but these usually improve with time. They include:nausea and vomitingrestlessness and agitationindigestiondiarrhea or constipationweight or appetite lossincreased sweatingdizzinessblurred visionsleepiness or insomniafeeling shakydry mouthheadachelow sex driveerectile dysfunctionsuicidal thoughts Serotonin syndrome Rarely, taking too much of a drug that boosts serotonin levels or combining two such drugs can lead to serotonin syndrome. This is a potentially life threatening condition that may require emergency treatment. Learn more about serotonin syndrome. SSRIs and suicide A person who uses SSRIs for depression will not experience the benefits at once. At first, symptoms may worsen before improving. Anyone experiencing thoughts of suicide should seek help at once. The FDA requires all antidepressants to carry a black box warning about the danger of suicide during the initial stages of treatment, especially in people under 25 years. Suicide prevention If you know someone at immediate risk of self-harm, suicide, or hurting another person:Ask the tough question: “Are you considering suicide?”Listen to the person without judgment.Call 911 or the local emergency number, or text TALK to 741741 to communicate with a trained crisis counselor.Stay with the person until professional help arrives.Try to remove any weapons, medications, or other potentially harmful objects. If you or someone you know is having thoughts of suicide, a prevention hotline can help. The 988 Suicide and Crisis Lifeline is available 24 hours a day at 988. During a crisis, people who are hard of hearing can use their preferred relay service or dial 711 then 988. Click here for more links and local resources. Therapy Doctors commonly recommend a combination of medication and therapy to treat depression. Several forms of psychotherapy can help manage symptoms of depression and other mental health conditions. Cognitive behavioral therapy and interpersonal therapy are the two main types. Learn more about psychotherapy. Natural remedies Some natural remedies may help boost serotonin levels in the body. These include:practicing meditationhaving light therapy, already in use for seasonal affective disorderdoing regular exerciseconsuming foods that are high in tryptophans Though there is not enough evidence to confirm that these methods can boost serotonin levels, in moderation, they are unlikely to be harmful. Learn more about how to boost serotonin levels. Foods Tryptophan is an amino acid that occurs in some foods. Some research links a higher intake of dietary tryptophan to more positive mood scores, possibly because tryptophan bolsters serotonin levels. Foods that may contain tryptophan include:turkeyeggscheesesoy productssalmon The body uses tryptophan to create serotonin. Eating foods that contain tryptophan may help support this process, but it does not mean that the body will necessarily absorb and use it. There is a growing interest among scientists in the idea that gut microbiota might influence the nervous system — including behavior, mood, and thinking — through a link known as the gut-brain axis. If so, serotonin could provide a crucial link. This suggests that diet and gut microbiota could play a role in preventing and treating conditions such as anxiety and depression. However, more research is necessary to confirm whether this is possible. Learn more about foods that may help boost serotonin levels. Takeaway Serotonin, or the “happy” chemical, appears to play a role in various physical and psychological functions. SSRIs are drugs that affect serotonin levels. They can help manage the symptoms of depression, although experts are still unsure exactly how it works. Anyone considering taking a drug or supplement that affects serotonin levels should consult their doctor first to ensure it is safe for them to use. Read the article in Spanish. Last medically reviewed on October 4, 2022DepressionEndocrinologyMental HealthNeurology / Neuroscience 11 sourcescollapsedMedical News Today has strict sourcing guidelines and draws only from peer-reviewed studies, academic research institutions, and medical journals and associations. We avoid using tertiary references. We link primary sources — including studies, scientific references, and statistics — within each article and also list them in the resources section at the bottom of our articles. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.Bamalan, O. A., et al. (2022). Physiology, serotonin.https://www.ncbi.nlm.nih.gov/books/NBK545168/Brain hormones. (2022).https://www.endocrine.org/patient-engagement/endocrine-library/hormones-and-endocrine-function/brain-hormonesChand, S. P., et al. (2022). Depression.https://www.ncbi.nlm.nih.gov/books/NBK430847/Cowen, P. J., et al. (2015). What has serotonin to do with depression?https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4471964/Depression. (2022).https://www.nimh.nih.gov/health/topics/depressionEl-Merahbi, R., et al. (2015). The roles of peripheral serotonin in metabolic homeostasis.https://www.sciencedirect.com/science/article/pii/S001457931500455X#Reuter, M., et al. (2021). Tryptophan-rich diet is negatively associated with depression and positively linked to social cognition.https://www.sciencedirect.com/science/article/abs/pii/S0271531720305534Selective serotonin reuptake inhibitors (SSRIs) information. (2014).https://www.fda.gov/drugs/information-drug-class/selective-serotonin-reuptake-inhibitors-ssris-informationSide effects: Selective serotonin reuptake inhibitors (SSRIs). (2021).https://www.nhs.uk/conditions/ssri-antidepressants/side-effects/Simon, L. V., et al. (2022). Serotonin syndrome.https://www.ncbi.nlm.nih.gov/books/NBK482377/What are MDMA's effects on the brain? (2017).https://www.drugabuse.gov/publications/research-reports/mdma-ecstasy-abuse/what-are-mdmas-effects-on-brainFEEDBACK:Medically reviewed by William C Lloyd III, MD, FACS — By James McIntosh — Updated on October 4, 2022 Latest newsWhat sets 'SuperAgers' apart? Their unusually large neuronsOmega-3 may provide a brain boost for people in midlifeSeasonal affective disorder (SAD): How to beat it this fall and winterCDC: Monkeypox in the US 'unlikely to be eliminated in the near future'Why are more women prone to Alzheimer's? New clues arise Related CoverageWhat is depression and what can I do about it?Medically reviewed by Nicole Washington, DO, MPH Depression is a common mental health problem that involves a low mood and a loss of interest in activities. 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