Symptoms of low serotonin may include mood changes, feelings of depression or anxiety, and difficulty with functions such as sleep and memory. Physical signs may include gastrointestinal symptoms or movement issues.

Serotonin is an essential hormone and neurotransmitter. It plays a role in a wide range of bodily functions, including sleep, appetite, mood, and thinking, but symptoms of a deficiency may be hard to spot.

The serotonergic system is highly complex, and scientists do not know precisely how it works. However, research links serotonin deficiency with conditions such as depression.

A better understanding of serotonin functioning may eventually lead to treatments for various conditions linked to low serotonin levels. However, for now, blood serotonin levels are not usually a reliable indicator of any specific disease.

This article explains what a person may notice if serotonin levels are low, why it happens, and how to address it.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Learn more.

Serotonin is a hormone that the body naturally produces. Serotonin deficiency occurs when a person does not have enough of this hormone, which may affect various bodily functions.

Much remains unknown about serotonin and how it works. However, researchTrusted Source links low serotonin activity with a range of mental health conditions, including:

Understanding serotonin

The central nervous system (CNS) produces and stores serotonin. The body uses anTrusted Source amino acid called tryptophan to produce serotonin.

Serotonin is a neurotransmitter that helps transmit messages in the CNS. However, it also contributes to the following functions:

Serotonin syndrome

Serotonin syndrome, also called serotonin toxicity, can occur if too much serotonin is active in the nervous system. This is a life threatening condition that may result fromTrusted Source medication use, the use of recreational drugs, or drug interactions.

Symptoms include:

A person with serotonin syndrome needs immediate emergency medical help.

Serotonin helps regulateTrusted Source a wide range of bodily functions. However, since its role in the body is part of a complex process, it can be challenging to determine whether low serotonin or something else is causing a specific symptom.

The sections below explain some possible symptoms of low serotonin levels.

Psychological symptoms

Research linksTrusted Source certain mental health symptoms with low serotonin activity, including:

  • Mood changes: Serotonin helps regulate mood. People who feel unusually irritable or down for no apparent reason may have low serotonin activity.
  • Depression: Feelings of sadness, hopelessness, and anger, as well as chronic fatigue and thoughts of suicide, may indicate depression.
  • Anxiety: A person with anxiety may worry excessively about specific issues or experience non-specific feelings of anxiety.
  • Dementia symptoms: Changes in certain serotonin receptors may contributeTrusted Source to behavioral and psychological symptoms of dementia, such as agitation, aggression, and apathy.
  • Sleep irregularities: Serotonin helps regulate sleep. Sleep problems may occur when there is an imbalance of serotonin.
  • Sexual function: Serotonin appears to affect sexual function. Medications that affect serotonin levels can have a complex effect on sexual function and drive.

In time, researchers may discover other ways low serotonin activity affects mental health.

Learn more about serotonin deficiency.

Help is out there

If you or someone you know is in crisis and considering suicide or self-harm, please seek support:

  • Call or text the 988 Lifeline at 988 or chat at 988lifeline.org. Caring counselors are available to listen and provide free and confidential support 24/7.
  • Text HOME to the Crisis Text Line at 741741 to connect with a volunteer crisis counselor for free and confidential support 24/7.
  • Not in the United States? Find a helpline in your country with Befrienders Worldwide.
  • Call 911 or your local emergency services number if you feel safe to do so.

If you’re calling on behalf of someone else, stay with them until help arrives. You may remove weapons or substances that can cause harm if you can do so safely.

If you’re not in the same household, stay on the phone with them until help arrives.

Role in physical health and possible symptoms

Serotonin may play a role in the nervous system. As such, it will affectTrusted Source the overall functioning of the body and may cause the following symptoms:

  • Gastrointestinal (GI) symptoms: Due to its role in the GI tract, changes in serotonin levels may lead to GI symptoms, including changes in appetite and bowel function.
  • Pain perception: Some people who experience psychological distress may have physical symptoms, such as chronic pain, with no apparent physical origin. A 2019 studyTrusted Source suggests that disruptions in the serotonin pathway may contribute.
  • Movement issues: Some research suggests boosting serotonin activity may help reduce resting tremors in Parkinson’s disease, suggesting low serotonin activity may play a role in worsening symptoms.
  • Blood clotting: Serotonin plays a role in blood clotting. A 2021 articleTrusted Source associates high serotonin activity with blood clotting. However, further research is necessary to understand the processes involved.
  • Wound healing: Some evidence suggestsTrusted Source that serotonin plays a role in wound healing by increasing cell migration to areas needing regeneration. More research is necessary to know if low serotonin levels affect the body’s healing ability.
  • Bone density: Some mouse studiesTrusted Source have suggested that low serotonin activity in some parts of the body may increase the risk of low bone density. However, more research is necessary to see if this applies to humans.
  • Pain: Various neurotransmitters, including serotonin, play a role in pain perception. Research associatesTrusted Source problems with the serotonergic system with painful conditions, such as irritable bowel syndrome (IBS) and fibromyalgia.

Doctors may diagnose low serotonin based on a person’s symptoms, not blood serotonin levels.

However, they may recommend a test to measure serotonin levels if they suspect a carcinoid tumor. These tumors start in certain body cells and can appear in the lungs, stomach, small intestine, rectum, and appendix.

A doctor may testTrusted Source for a substance called 5-hydroxy indoleacetic acid (5-HIAA) if they suspect someone has a carcinoid tumor. When serotonin undergoes oxidative reactions, 5-HIAA forms, and the body eliminates it in urine.

A doctor may prescribe medications or suggest lifestyle changes to help someone maintain their serotonin levels.

Medications

Medications can boost serotonin activity. These drugs include the following antidepressants:

They work in different ways. According to the UK’s National Health Service (NHS), doctors prescribe SSRIs and SNRIs more often than the older style MAOIs, which can have adverse effects.

Lifestyle changes

Doctors may suggestTrusted Source certain lifestyle changes or non-medicinal treatments for people with symptoms of low serotonin, such as:

  • Psychotherapy: Psychotherapy may improve the symptoms of various mental health conditions, including anxiety and depression.
  • Manage stress: Chronic stress may affect how the brain processes or produces serotonin and may lead to a wide range of symptoms, such as mood changes. Managing stress may help keep serotonin neurotransmission stable, and this may help regulate mood.
  • Light therapy: A doctor may suggest light therapy to help with mental health problems such as seasonal affective disorder (SAD). This may boost serotonin production and improve mood.
  • Exercise: ResearchTrusted Source suggests exercise can help raise serotonin levels, boost mood, and manage depression.
  • Dietary changes: Some researchTrusted Source suggests that various dietary nutrients could help boost serotonin levels, including foods containing the amino acid tryptophan.

More about lifestyle changes to balance serotonin levels

Serotonin function may vary between males and females.

Estrogen, which is higher in females, can affect the production, use, and degradation of serotonin. According to a 2019 reviewTrusted Source, animal studies suggest that boosting estrogen levels may lead to an increase in serotonin.

However, it may depend on how long estrogen treatment lasts. In one study, serotonin levels fell as estrogen therapy progressed.

Serotonin plays a role in many aspects of health, and a deficiency could occur, leading to a wide range of medical conditions.

Moreover, not everyone with symptoms of depression or other mental health conditions will have low serotonin. Symptoms alone will not show if a person has low serotonin activity.

A person should see a doctor for the following reasons:

  • feelings of sadness or anxiety that do not improve with self-care
  • memory loss
  • movement issues
  • changes in sleep, appetite, or digestion
  • any side effects due to serotonin-related treatments
  • signs of serotonin toxicity, especially after taking prescription or recreational drugs

How does someone know if they have serotonin deficiency?

It is not possible for an individual to know if their serotonin levels are low. However, people who see a doctor with persistent symptoms of depression may benefit from medication and lifestyle measures that regulate serotonin function.

How can someone fix serotonin deficiency?

Medications, such as SSRIs or SNRIs or lifestyle changes can help people boost their serotonin levels. A healthcare professional may suggest regular exercise, dietary changes, and stress management.

Does low serotonin cause anxiety?

Research associates low serotonin activity with certain mental health conditions, such as anxiety disorders. However, other factors, including trauma, medications, and childhood experiences, may also causeTrusted Source anxiety.

Serotonin contributes to a wide range of bodily functions, and many aspects of well-being may depend on a balance in serotonin activity. Low serotonin levels may have links to certain mental health issues.

However, measuring serotonin levels is not usually how doctors diagnose a health condition. A doctor will likely focus on a person’s symptoms, carry out other tests, and then treat the condition they diagnose.

Some conditions may respond well to treatments that boost serotonin activity in the body, such as SSRIs, SNRIs, or lifestyle changes, including regular exercise and dietary changes.