How To Balance Serotonin

Serotonin is an important neurotransmitter and hormone in the human body that contributes to a range of bodily functions and is involved in mental health. Imbalanced serotonin levels occur when there is either too much, or too little serotonin in one's body, and can lead to a range of physical and psychological symptoms. Lower serotonin levels are thought to contribute to psychological conditions such as anxiety and depression. 

In this article, we explore the causes and symptoms related to serotonin imbalance, as well as ways to balance levels within the body. These include medications that can improve symptoms and natural ways to increase serotonin levels, such as sunlight and exercise.

About Serotonin

Serotonin, or 5-hydroxytryptamine (5-HT), acts as both a neurotransmitter and a hormone within the human body.1 Neurotransmitters send chemical messages directly from the brain to the rest of the body and nervous system. These messages are involved in vital processes that are needed to control daily functions in the body, including the regulation of sleep, sexual behaviour, appetite, and aggression. Serotonin also plays a significant role in memory, learning, and happiness. It is known as the ‘happy hormone’, and influences associated emotions and moods.2 

The majority of serotonin is found within the gut and intestines (about 90%), where it is then released into the blood. Only 10% of serotonin production is thought to occur in the brain.3

Serotonin imbalance occurs when serotonin levels in the body are either too high (serotonin syndrome) or low (serotonin deficiency).4 As serotonin is one of the most important neurotransmitters influencing mental health, imbalanced levels can be linked to a range of physical and mental health conditions.5  

Signs of serotonin imbalance

A serotonin imbalance can have diverse effects throughout the human body and may affect different people in different ways.

Symptoms of serotonin syndrome typically occur within hours of changing the dose of medication or taking a new drug, and include:6

  • Hyperthermia
  • Agitation or restlessness
  • Ocular clonus (slow, continuous, and horizontal eye movements)
  • Tremors
  • Insomnia
  • Confusion
  • Rapid heart rate and high blood pressure
  • Dilated pupils
  • Loss of muscle coordination (or twitching) 
  • High blood pressure
  • Muscle rigidity or stiffness
  • Heavy sweating
  • Increased bowel movements
  • Diarrhoea
  • Headache
  • Shivering
  • Goosebumps

More severe symptoms can be life-threatening and require immediate medical attention, including high fever, irregular heartbeats, seizures, and unconsciousness. If you suspect you have serotonin syndrome, you should contact your healthcare provider straight away.7

Low serotonin levels are associated with a range of psychological symptoms and mental health conditions including:8

  • Feelings of sadness
  • Feelings of low mood
  • Feeling tense or irritable
  • Low energy
  • Suicidal thoughts
  • Reduced interest in sexual behaviours
  • Sleep problems
  • Concentration and attention difficulties
  • Memory issues
  • Anxiety
  • Aggression
  • Depression

As serotonin is involved in the overall functioning of the nervous and immune systems, there can also be a range of physical symptoms and health conditions related to serotonin deficiency, including:

  • Digestive problems
  • Changes in appetite
  • Muscle pain
  • Blood clotting
  • Slow wound healing
  • Pain
  • Migraines

Causes of serotonin imbalance

Serotonin syndrome (or toxicity) occurs from increased serotonin levels in the body. This is also known as serotonergic overactivity and is typically caused by starting serotonergic drugs (those that affect serotonin levels in your body) or changing their dosage.8 Most cases are mild and occur when you combine serotonergic drugs, such as migraine or opioid pain medication, and antidepressants.9 Serotonin syndrome can also be caused by interactions between medication and therapeutic or recreational drugs, as well as by intentional overdose.

Serotonin deficiency (or serotonin depletion) is caused when your body is not receiving or producing enough serotonin. For example, your body may not be able to use available serotonin if the serotonin receptors are not functioning correctly.10

It is not fully understood why some people have serotonin deficiency, and in many cases, there is no clear cause. However, factors thought to contribute include:11

  • Genetic factors
  • Age-related health and brain changes
  • Hormone imbalances
  • Chronic stress
  • A lack of exposure to natural light
  • Lack of physical activity
  • Chronic pain
  • Poor diet 

It is important to note that the causes of serotonin imbalance are not fully understood, and may differ from person to person. 

Diagnosis of serotonin imbalance

It can be difficult to diagnose serotonin imbalance, given that its severity varies and that many of its symptoms may be common to other clinical conditions. Blood tests are rarely used to diagnose serotonin imbalance, as this does not accurately reflect serotonin activity or levels in the brain.

Diagnosing serotonin syndrome requires a clinical examination from a medical professional. This involves looking at your physical symptoms, as well as any medications you are taking. There are no specific diagnostic criteria for determining serotonin deficiency, and symptoms are typically discussed with medical providers at length. 

Serotonin is part of a complex process in the body, and it can be difficult to determine whether imbalanced levels are causing specific symptoms alone. It is possible that serotonin deficiency occurs as a result of symptoms or conditions in the first place, or due to combinations and interactions of these symptoms.1 

Ways to balance serotonin levels

Symptoms of increased serotonin levels are typically mild and go away within days of stopping the medication that caused the symptoms. Another way to balance serotonin syndrome symptoms is to take drugs that block serotonin. You should seek medical attention and care if you believe you have serotonin syndrome and have changed medication or dosage.12

Due to the many potential causes of low serotonin levels, there are several ways to improve symptoms and increase serotonin levels or activity:


Antidepressants are one type of medication that boosts serotonin activity and focuses on increasing the amount of serotonin available in the brain. There are several types that work in different ways, including selective serotonin re-uptake inhibitors (SSRIs), serotonin-nor adrenaline reuptake inhibitors (SNRIs), and nor-adrenaline and specific serotonergic antidepressants (NASSAs).8 Antidepressants can have side effects, and a doctor should be consulted before taking this medication to ensure the correct type is chosen to suit your lifestyle and symptoms.

Antidepressants are mostly used to treat clinical depression. However, they are also used for other mental health conditions and long-term pain. It is unclear whether antidepressants directly address the cause of serotonin deficiency, or rather just improve symptoms. Therefore, they are often prescribed alongside cognitive behavioural therapy to treat more severe mental health conditions.13

Cognitive behavioural therapy

Cognitive behavioural therapy (CBT), known as talking therapy, can help to manage symptoms of serotonin deficiency by changing the way you think and behave. CBT focuses on helping someone understand their feelings and feel more prepared for challenges by tackling thoughts in a positive way. It can help to relieve and improve symptoms of various mental health conditions, including depression, anxiety, insomnia, bipolar disorder and post-traumatic stress disorder.

Some studies suggest that CBT is as effective as medication for improving symptoms of depression, and may work by regulating serotonin activity.14 One study suggested that therapy increases the number of serotonin receptors in the brain, therefore increasing the amount of serotonin available.

Stress management techniques

Chronic stress can lead to many of the symptoms associated with a serotonin deficiency, and finding ways to manage stress can help to balance serotonin levels.15 This can help to regulate mood and other related symptoms too. Examples of how to minimise stress can be found here, and include being active, avoiding unhealthy habits and trying to think positively. 


Studies have shown that increased exposure to sunlight (UV light) can increase serotonin in your brain.16 Sunlight is needed to synthesise vitamin D in the body, which activates the synthesis of serotonin.17 Therefore, spending more time outside in the sun can be a natural way to increase your serotonin levels, boost your mood and improve symptoms of serotonin deficiency.

Light therapy

Light therapy involves exposing the individual to an artificial light source, to mimic the positive effects of sunlight on serotonin levels. This may be an especially beneficial option for those who cannot spend time outside in natural sunlight, or for those with seasonal affective disorder (SAD).16 Studies have shown light therapy to improve symptoms and boost serotonin function even days after starting treatment.18


Serotonin is made from tryptophan, an amino acid that cannot be produced in your body alone, and has to be acquired from food in your diet. Studies have suggested that increasing tryptophan levels can increase the production of serotonin in your body, and can improve symptoms of serotonin imbalance.19 Foods high in tryptophan are known as serotonin-boosting foods and include salmon, poultry, eggs, dairy products, tofu, fruits, and seeds. However, converting tryptophan to serotonin is a complex digestive process, and eating a high-tryptophan diet may not increase serotonin levels alone.

Taking a vitamin D supplement may also help to synthesise more serotonin, or eating a diet high in vitamin D, including foods such as fish, orange juice and dairy products.17 


A large body of research has shown that regular exercise can reduce symptoms related to serotonin deficiency, including improving mental health conditions such as anxiety and depression.20 Lack of exercise is also considered a significant risk factor for these mental health conditions, as well as many physical conditions or diseases. Exercising for at least 30 minutes three times a week, for example, walking, yoga or stretching, is thought to improve and regulate serotonin levels.8


Serotonin imbalance occurs when there is either too much (serotonin syndrome) or too little (serotonin deficiency) serotonin in your body. Typically serotonin syndrome occurs by changing the dosage of medication or starting a new medication that affects serotonin levels. Associated symptoms typically go away within days of stopping the medication, and doctors should be consulted immediately. 

Serotonin deficiency can cause a variety of negative effects on the body and mind. However,t can be difficult to determine the exact underlying cause of these symptoms. It is possible to increase your serotonin levels in several ways, including via medication or naturally through changing your diet, increasing your exercise, and getting more sunlight.


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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Isabella Underhill

BSc (Hons) Psychology, University of Bath

Isabella Underhill is a dedicated medical and health writer who showcased her expertise during her internship with Klarity. There, she excelled in producing scientific health articles, making complex terminologies accessible to the general reader. Her passion for psychology and mental health topics is evident in her contributions to Klarity's health library. Isabella also gained hands-on clinical experience during her placement at the Royal Free London NHS Foundation Trust. Working in Clinical Immunology and Plastic Surgery departments, she collaborated on both clinical and research aspects of patient care, emphasizing her diverse skill set in the health sector.

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