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How To Increase Your Serotonin Levels Naturally

Medically reviewed by 
How To Increase Your Serotonin Levels Naturally

This is part 2 of a 6 part series on a functional medicine approach to neurotransmitter imbalances. This article will provide an overview of the role of serotonin in the body, symptoms of having high or low levels, and functional medicine labs that will help guide treatment of the root cause of serotonin imbalances.

As we learned in the first part of our series, neurotransmitters, in general, act as chemical messengers in the body that help neurons communicate with each other and can influence everything from mood to cravings to our sleeping patterns. Serotonin is one of the most well-known neurotransmitters in the functional medicine world. Often referred to as "the happy hormone," but as you are about to learn, serotonin influences much more than our mood.


What is Serotonin?

Serotonin, also known as 5-hydroxytryptamine (5-HT), is an inhibitory neurotransmitter that plays a role in emotion, mood, digestion, appetite, and sleep; it also acts as a hormone. It is secreted by neurons of the brainstem and neurons that innervate the GI tract, which is why you might have experienced a "nervous stomach" or "butterflies in your tummy."

Roughly 95% of serotonin is found in the cells that line your gastrointestinal tract and is released into your blood circulation, while about 10% is produced in your brain. It is made from the essential amino acid tryptophan (1).

What Causes Low Serotonin?

1. Stressors

The accumulation of excessive life stressors, combined with the inability to mitigate prolonged periods of stress, can negatively impact serotonin levels throughout the body. Inadequate sunlight and lack of exercise have also been shown to increase stressors in the body and lower serotonin production.

2. Toxins

Environmental toxins such as heavy metals, pesticides, drug use, and prescription drugs can cause permanent damage to the nerve cells that make serotonin and other neurotransmitters. (5).

3. Substances

Certain drugs and substances such as caffeine, alcohol, nicotine, NutraSweet, antidepressants, and some cholesterol-lowering medications deplete serotonin and other neurotransmitters.

4. Antidepressants

Antidepressants block serotonin's reuptake back into serotonin neuronsprescription. Monitoring serotonin levels when on any medications is crucial.

5. Hormones

Hormonal shifts, such as during pregnancy, menopause, or beginning and stopping oral contraceptives, and our monthly menstrual cycle (as serotonin levels are lowest two weeks before your period, known as the luteal phase), can all influence levels of serotonin throughout the body.

6. Diet

Impaired absorption and breakdown of food reduces our ability to build serotonin. Neurotransmitters require specific vitamins and minerals called "cofactors," as well as carbohydrates, to be converted into serotonin.

Research has shown that the absence of carbohydrates over extended periods can prevent tryptophan from entering the brain, a precursor needed for conversion into serotonin (6).

7. Sleep

Poor quality sleep plays a role in low serotonin levels, as serotonin is needed to make melatonin (which regulates your sleep). Therefore, serotonin levels might also be low when sleeping patterns are inconsistent or poor.

8. Neuroinflammation

An exciting area of research that continues to grow is the role of neuroinflammation and its impact on mood disorders, such as anxiety and depression, which ultimately can impact serotonin levels. This research focuses on the role of the kynurenine pathway and serotonin imbalances. Tryptophan should be converted into serotonin; however, if there are excessive amounts of inflammation, these inflammatory cytokines can cause tryptophan not to be converted to serotonin but rather to be diverted down a different pathway known as the Kynurenine Pathway (KYN) (2).

Upon activation, the kynurenine pathway takes available tryptophan (the precursor of serotonin) away from serotonin production and begins to break it down into neurotoxic kynurenine metabolites, which include 3-hydroxykynurenine and quinolinic acid, which have a toxic influence on the central nervous system, leading to symptoms of depression and anxiety (3, 4).

Low Serotonin Signs & Symptoms

  • Mood imbalances (such as anxiety and or depression)
  • Memory issues
  • Changes in sleep (as serotonin helps regulate sleep)
  • Slow wound healing
  • GI discomfort and digestive issues (including constipation, bloating, and slow peristalsis)

Functional Medicine Lab Test to Treat Root Cause of Low Serotonin

It is important to note that when it comes to neurotransmitter levels in general, it is not always the case that certain levels just happen to be low or high, but rather imbalanced relative to other neurotransmitter levels in the body.

A level might be low relative to the "normal" range of other neurotransmitters, making symptoms worse and even masking deeper rooted issues. A functional medicine approach looks at optimal test results values to help determine the diagnosis's exact root cause.

Neurotransmitter testing allows practitioners to look deeper into specific neurotransmitters and neurotransmitter metabolites such as KNYA and Quinolinic Acid, which can impact mood and influence serotonin levels.

The Neurotransmitters + Micronutrients test analyzes the status of neurotransmitters, their precursors, and their derivatives, which allows the patient and the practitioner to take a more holistic approach to treat imbalances.

Another option is the Comprehensive Stool Test, as our gut bacteria play a significant role in the production of neurochemicals such as serotonin.

The gut manufactures roughly 90-95% of total body serotonin, which can influence overall GI function and mood. The GI-MAP test uses qPCR technology to measure a variety of gastrointestinal microbiota DNA, microbial imbalance, and inflammation.  

Retesting these levels every 90 days is considered standard to see if functional medicine protocols need to be adjusted.

Low Serotonin Conventional Treatment Options

Conventional treatment for low serotonin levels includes antidepressant medication or selective serotonin reuptake inhibitors (SSRIs), which work by inhibiting the uptake of serotonin, which can increase serotonin activity.

Functional Medicine Treatment Options

Functional medicine treatment options focus on the root cause of lower serotonin levels and modify dietary and lifestyle factors based off of lab results to positively influence serotonin levels throughout the body.

1. Exercise

Exercise, for example, is associated with an increase in plasma tryptophan and a decrease in the plasma level of the branched-chain amino acids (BCAAs) leucine, isoleucine, and valine (which are all tryptophan inhibitors). This increase in plasma tryptophan leads to increased availability of tryptophan in the brain, which converts to serotonin (8).

2. Stress Reduction & Exposure to Natural Light

Stress reduction and exposure to natural bright light can help support serotonin levels by helping to regulate the circadian rhythm and balance hormones such as melatonin and support healthy sleeping patterns, which can play a role in mood regulation (9).

3. Dietary Needs to Make Serotonin

To make serotonin, the body needs tryptophan, which converts into 5-HTP, with the help of various cofactors such as B6, Magnesium, Vitamin C, Zinc, Iron, and B-9, therefore including foods that are rich in these nutrients is a great way to support serotonin levels.

Vitamin D3 and Omega-3 fatty acids can help to normalize serotonin levels by helping to regulate the conversion of tryptophan into serotonin (13).

Focusing on dietary changes such as including quality protein, getting enough carbohydrates in the diet, and incorporating serotonin-supporting foods such as salmon, eggs, turkey, chicken, pineapple, bananas, potatoes, strawberries, sunflower seeds, and wild rice is a wonderful natural option (8).

4. Supplements

Based on lab results, supplementation with serotonin precursors such as 5-HTP, L-theanine, and specific probiotic strains such as Lactobacillus Brevis, Bifidobacterium dentium, and Lactobacillus Plantarum can help influence the production of serotonin (10).

Serotonin Syndrome

High serotonin levels can be referred to as Serotonin Syndrome and manifest as restlessness, agitation, diarrhea, confusion, and muscle twitching. This can be caused by medications that build up high levels of serotonin in the body, such as antidepressants, opioids, and certain migraine medications (11).

Common Medications & Supplements Associated with Serotonin Syndrome:  

  • Selective serotonin reuptake inhibitors (SSRIs)
  • Serotonin and norepinephrine reuptake inhibitors (SNRIs)
  • Bupropion
  • Tricyclic antidepressants
  • Monoamine oxidase inhibitors (MAOIs)
  • Anti-migraine medications
  • Pain medications
  • Lithium (Lithobid), a mood stabilizer
  • Herbal supplements: (including St. John's wort, ginseng, and nutmeg)
  • Over-the-counter cough and cold medications containing dextromethorphan (Delsym)
  • Anti-nausea medications
  • Linezolid (Zyvox)
  • Ritonavir (Norvir)
  • Illicit drugs (including LSD, ecstasy, cocaine, and amphetamines)

Increased Risk of Serotonin Syndrome is Possible if a Patient:

  • Recently started taking or increased the dose of a medication known to increase serotonin levels
  • Took more than one drug known to increase serotonin levels
  • Took herbal supplements known to increase serotonin levels
  • Used an illicit drug known to increase serotonin levels

High Serotonin Signs & Symptoms

High levels of serotonin may be associated with health issues such as:

  • Restlessness
  • Panic disorders (such as social anxiety)
  • Agitation
  • Diarrhea
  • Confusion
  • Rapid heart rate and high blood pressure
  • Dilated pupils
  • Loss of muscle coordination or twitching muscles
  • High blood pressure
  • Muscle rigidity
  • Heavy sweating
  • Shivering

Functional Medicine Lab Test to Find Root Cause of High Serotonin

As stated earlier, high levels of any molecule or nutrient in the body are generally a myopic view of trying to figure out what is going on from a more holistic perspective. Therefore it is a good idea to use the same tests which assess low levels when looking at high levels of serotonin.

The Neurotransmitters + Micronutrients test is one of the most comprehensive tests for assessing neurotransmitter function and levels. This test analyzes the status of neurotransmitters, their precursors, and their derivatives, which allows the patient and the practitioner to take a more holistic approach towards treating imbalances.

Some individuals with the MTHFR genetic mutation may have a tendency to overproduce serotonin, leading to excessive amounts in the brain. They may also have higher blood levels of copper and lower levels of zinc.

High Serotonin Functional Medicine Treatment Options

When we see high serotonin levels, this can be due to a drug reaction. Generally, it is caused by medications that can lead to a build-up of increased serotonin levels in the body; therefore, the first step would be working with your doctor to look at the current dosage and combinations of medications if you have started taking any new drugs or medications.


Serotonin is an inhibitory neurotransmitter in the central nervous system that plays a role in emotion regulation, mood, digestion, and sleep. Symptoms of low serotonin levels include mood imbalances, changes in sleep, and digestive issues, while signs of high serotonin levels include restlessness, agitation, and social anxiety.

Many dietary and lifestyle factors can positively influence serotonin levels throughout the body, such as exercise, diet changes, and identifying imbalances in neurotransmitter levels and metabolites through various functional medicine labs.

The information provided is not intended to be a substitute for professional medical advice. Always consult with your doctor or other qualified healthcare provider before taking any dietary supplement or making any changes to your diet or exercise routine.
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