Optimal Result: 61 - 103.2 µg/g creatinine.

Serotonin plays important roles in the resolution of mood, sleep, and appetite.

Serotonin is an inhibitory neurotransmitter synthesized by enzymes that act on tryptophan and/or 5-HTP.

Neurotransmitters are divided into two basic categories:

– Excitatory neurotransmitters stimulate the brain and body.

– Inhibitory neurotransmitters calm the brain and body.

Just as levels of individual neurotransmitters are important in maintaining optimum health, so is the proper balance between your excitatory and inhibitory systems.

Serotonin, generally regarded as the “happiness molecule,” contributes to the feelings of calm and well-being that eases depression and anxiety, supports sleep, and decreases appetite.

Serotonin is stored in presynaptic vesicles and released to transmit electrochemical signals across the synapse. Extensive research has been conducted surrounding serotonin and acts as a target for symptoms like low mood, compulsions, anxiousness, and headaches.

Serotonin acts, in most cases, as an inhibitory neurotransmitter and, like GABA, modulates neuron voltage potentials to inhibit glutamate activity and neurotransmitter firing. Serotonin neurons have large numbers of axons and are important in integrating neural circuits. This also provides an explanation for serotonin’s role in so many health concerns.


– How to increase serotonin in the human brain without drugs [L]

– Carcinoid Syndrome [L]

What does it mean if your Serotonin result is too low?

Serotonin is lower than the reference range. Generally regarded as the happiness molecule, serotonin has calming effects and contributes to the feelings of well-being. Serotonin elevates mood, decreases anxiety, appetite, and libido, improves sleep and memory, eases depression, and helps regulate body temperature. Most of serotonin in the human body is produced in the gastrointestinal tract, where it stimulates gut motility.

Symptoms of low serotonin levels:

– Depression / Low mood

– Anxiety

– Sleep difficulties

– Uncontrolled appetite / Carbohydrate cravings

– Headaches

– Hot flashes

– Constipation

When serotonin is low, supplementation with cofactors to promote biosynthesis (e.g. vitamin B6), precursors (tryptophan/5-HTP), L-theanine, and probiotics may be helpful. Additionally, lifestyle modifications, such as regular exposure to bright light, healthy diet, sufficient exercise, and positive self-talk are all effective strategies that result in increased serotonin levels. [L]

What does it mean if your Serotonin result is too high?

Serotonin arises from tryptophan metabolism, and is broken down to 5-hydroxyindole acetic acid (5-HIAA) by monoamine oxidase A (MAO A).

Adequate serotonin levels are necessary to support:

- mood,

- decrease anxiety,

- improve sleep and memory,

- and prevent depression.

Too much serotonin, however, can contribute to undesirable symptoms of:

- agitation,

- restlessness,

- confusion,

- rapid heart rate,

- high blood pressure,

- sweating,

- nausea,

- diarrhea,

- and headaches.

Research on urinary serotonin and 5-HIAA is scarce, however, high plasma levels of both serotonin and 5-HIAA have been reported in patients with depression (Mitani, et. al. 2006). Some studies show that urine and plasma levels of serotonin may correlate (Audhya, et. al. 2012).

High serotonin in the body is commonly associated with changes in gastrointestinal (GI) health resulting from increased numbers of serotonin-producing enterochromaffin cells in response to chemical, mechanical or neurological insults (Manocha, et. al. 2012). Compromised GI health may be a contributing factor to the self-reported symptom of depression (Clapp, et. al. 2017; Mayer, et. al. 2015; Wang and Kasper, 2014).

Medications may also contribute to elevated serotonin levels, these include but are not limited to:

- tryptophan,

- 5HTP,

- monoamine oxidase inhibitors,

- methyldopa,

- morphine,

- and reserpine.

Foods containing high concentrations of tryptophan can elevate urinary serotonin levels; these foods include:

- walnuts

- pineapples,

...and to a lesser extent:

- bananas,

- avocados,

- beans,

- cantaloupe,

- dates,

- eggplant,

- grapefruit,

- kiwi,

- lentils,

- meats,

- plantains,

- seeds,

- tomatoes,

- tuna,

- and turkey.

It is important to note that while these foods may elevate urinary levels of serotonin and are a reflection of their interaction with the GI tract (majority of serotonin is produced in the GI tract), and in this case, food-derived elevated urinary serotonin is not representative of serotonin levels in the brain.

Potenetial treatment considerations:

Consider avoiding foods that raise urine serotonin levels artificially. If symptoms of high serotonin are problematic, consider evaluation of current medication to aid in reducing serotonin levels. Addressing gut health if symptoms are present may be beneficial. Therapeutic strategies that employ vitamin B2 supplementation and/or SAMe may aid to lower serotonin levels by promoting metabolism.

Cofactor support for high serotonin levels:

– copper (with zinc),

– Acetyl Coa,

– SAMe

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