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Written By: James Dixon

James has a Masters degree in Philosophy, has a background as a personal trainer, writes for various health and nootropics publications and is also a published author. All of his experiences and qualifications to date, mean he is incredibly well placed to test, research and review nootropics - which is his main role here at Peak Nootropics.

Serotonin is a vital chemical messenger that carries information between your brain’s nerve cells and throughout your body. Various bodily functions rely on it, including for mood regulation, digestion, sleep, recovery, wound healing and blood clotting, sexual function and libido.

Balanced serotonin levels are key to your ongoing physical and mental wellbeing. If your serotonin levels are unbalanced – either too high or too low – various health concerns can follow.

What is serotonin?

Serotonin, or 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter that additionally operates as a hormone. It is created from tryptophan, an essential amino acid. As an essential acid, tryptophan cannot be produced by your body – you need to take in exogenous sources through diet and supplementation.

Serotonin brain pathways

Neurotransmitters are, as their name suggests, chemicals that transmit messages between your brain’s nerve cells (your central nervous system, or CNS), and then throughout your body (your peripheral nervous system (your peripheral nervous system, or PNS). The information contained in these messages essentially enables your body to function properly.

Serotonin is concerned with several facets across your body’s many roles. It can influence your mood, particularly your happiness and sense of wellbeing, and your learning capabilities, in addition to aiding body temperature regulation, sleep quality and patterns, sexual health and libido, and appetite. Low serotonin levels are often thought to lie behind conditions like depression, anxiety, and mania, among other things.

Your gut contains most of your body’s serotonin – around 90% of it is held within the cells lining your gastrointestinal tract. This is then released into your bloodstream, from where it is then absorbed by platelets. Your brain contains most of the remaining 10%.

Serotonin and dopamine come hand in hand. They are often spoken about in similar terms, for very good reason.

They are both key chemical messengers, neurotransmitters intimately involved in various similar processes. Each is associated with mental wellbeing and satisfaction levels, making it easy to think of them almost synonymously.

They aren’t synonymous, however. There are some crucial differences between the two:

For instance, where serotonin is stored largely in the gut, dopamine is found mostly in the brain. They influence your mood differently, too.

Serotonin is responsible for your mood and anxiety levels, whilst dopamine is concerned largely with motivation, reward, and pleasure. Serotonin is targeted by common depression treatment plans, whilst dopamine isn’t.

Finally, they both play a role in energy levels, but both through different mechanisms. Serotonin helps in sleep and wakefulness regulation whilst dopamine helps you to feel more alert and switched on.

Serotonin’s role in your body

As mentioned above, serotonin is a neurotransmitter. Thus, it works by enabling signals to travel between the cells of your CNS and PNS. It plays a central role in a great many bodily functions, including bowel movements, sleep patterns, mood regulation, and so on.

Mood regulation

This is perhaps one of the more serious roles we see serotonin playing within your body. Optimal levels are crucial for healthy mood regulation. They can help you to feel happier, calmer, more focussed, with fewer mood swings and a greater sense of stability.

Low levels can lead to anxiety, depression, and a lack of focus, as a result. Many treatment plans for depression and associated conditions work in large part by boosting serotonin levels in the brain.


Sleep works in conjunction with dopamine to help regulate sleep quality – duration and quality of sleep. Your brain needs serotonin to create melatonin, the main hormone in control of your sleep-wake cycle.

Recovery and healing

One of serotonin’s lesser-known roles is in wound healing. It is released by blood platelets to help wounds to heal – it slows blood flow by narrowing the arteriole blood vessels, which in turn enables clotting.

Digestive health

As above, the vast majority of your body’s serotonin is stored in the gastrointestinal (GI) tract. Here, it helps to enable healthy bowel function whilst also helping to ringfence your gut health. Your gut can bolster serotonin levels in order to detox, more speedily digesting to get toxic products out of your system. It is also key to satiation, diminishing your appetite as you eat.

Bone health

Bone health also relies on optimal serotonin levels. Excessively high serotonin levels in the gut have been associated with weakened bones, and thus a greater susceptibility to fractures and osteoporosis.

Sexual function

Serotonin pairs up with dopamine once more to regulate your sexual desire, your libido. Drugs that commonly alter serotonin levels, like common antidepressants, can greatly impair your libido.

Serotonin and mental wellbeing

Low serotonin levels have been associated with a slew of common mental health concerns. These include the likes of depression, anxiety, and mood and psychological disorders like bipolar disorder and schizophrenia, as well as obsessive compulsive disorder (OCD), post-traumatic stress disorder (PTSD), anxiety disorder, and phobias.

image showing body chemistry

As a result, as we have seen, plenty of common mental health treatment plans use medications like SSRIs (selective serotonin reuptake inhibitors) to change serotonin levels or the ways in which your brain makes use of serotonin. Things have become a little more complex of late, but early mental health theory posited that low serotonin causes depression. There is a link, but the causal relationship is very much up for debate.

However, even given this need for debate, anti-depressant medications are still a valuable tool in treating mood disorders, especially when combined with other therapies. For instance, SSRIs combined with CBT therapy and lifestyle factors and coping mechanisms like creative output, exercise, and a strong community represents a fantastic treatment plan for depression.

Serotonin regulating drugs are also commonly prescribed for disorders like bipolar disorder and OCD, PTSD, and anxiety and panic disorders, as above, as well as bulimia, migraine, and several others.

These treatments seek to stabilize a patient’s serotonin levels between 101 and 283 nano-grams per milliliter, though we can only measure serotonin blood levels, not serotonin brain levels, which are obviously far more relevant for mental health management.

Serotonin differences between men & women

There may be several differences between the way in which men and women each use serotonin. This is largely due to estrogen’s impact on serotonin. Estrogen is typically higher in biological women. It can impact serotonin’s production, use, and degradation. In fact, tentative data taken from animal studies have suggested that raising estrogen levels may lead to an increase in serotonin levels, for better or worse.

This may depend on the length of estrogen treatment. Some research data have shown serotonin levels fall over time as estrogen use continued.

Serotonin deficiency

There are some very notable symptoms associated with low serotonin levels.

Largely, it can lead to low mood, memory problems, and low libido. These may be the first signs you notice within yourself if you are experiencing serotonin deficiency. They are depression symptoms, of course, though there is as yet no confirmed link between depression and low serotonin levels. We can only imply one from these symptoms.

Overcoming serotonin deficiency

There is usually more than one cause of serotonin deficiency. Serotonin levels can be called low because of a couple of things – either you are underproducing it, or your body isn’t using it effectively, for instance if you don’t have an adequate number of serotonin receptors, or if these receptors aren’t working properly.

You can overcome both of these using medication. There are also some lifestyle changes you can make in order to boost your natural serotonin output. These can include eating more foods that contain tryptophan, from which serotonin is made, as well as being more active and less stressed, and getting outdoors more, particularly in sunny weather.

Eating for higher serotonin output

Luckily, there are plenty of foods that give you plenty of tryptophan. Packing your diet with them represents a great way to give your body everything it needs to optimize serotonin output.

Foods containing large amount of tryptophan include:

  • Salmon
  • Turkey
  • Cheese
  • Eggs
  • Tofu
  • Pineapple
  • Nuts, oats and seeds

Do note that simply eating more of these foods may not necessarily help with serotonin output in isolation.

Serotonin output is incredibly complex and only partially understood. Researchers are still studying the effects of high-tryptophan content food on serotonin levels. You also need plenty of good quality carbohydrates to help your body in absorbing amino acids, including tryptophan. Tryptophan may also find itself in competition with other amino acids for uptake in the bloodstream, meaning less getting into your brain.

Several supplements may also help you to increase serotonin levels. These include straight tryptophan as a dietary supplement, probiotics and SAMe, or the herbal supplements ginseng, St. John’s wort, nutmeg, and Syrian rue.

Getting outdoors to boost serotonin output

We should all spend as much time outdoors as possible. It can alleviate stress, anxiety, and depression by itself – nature’s healing power is well-studied and well-documented.

Sunlight is also a good fix for low serotonin output. A lack of it can result in seasonal affective disorder, or SAD, a mood disorder hallmarked by depression and lethargy. Just ten to fifteen minutes of sunlight daily can make a difference, boosting both serotonin and vitamin D levels.

Light therapy can work as a good substitution during darker, colder months, or in less sunny climates.

Physical activity

Regular physical activity is a good thing across the board for pretty much every facet of your health and wellbeing. As part of this, it can help to optimize serotonin output. Half an hour or so of daily or near-daily aerobic exercise performed in conjunction with two resistance training sessions per week can alleviate the symptoms of mood disorders, in large part by bolstering serotonin output.

Meditation and mindfulness

Meditation and mindfulness practice can greatly alleviate and diminish stress and anxiety levels. They each promote positive mindsets and have been shown to improve long term stress resistance, even possibly altering gut bacteria to promote health and wellbeing. They may also raise serotonin levels, particularly due to their stress relieving properties, though more research and data are needed.

Excess serotonin – serotonin syndrome

Serotonin syndrome occurs where there are excessive amounts of serotonin in your system, or when it is increased too drastically. It most commonly occurs when you are on a medication known or intended to increase serotonin levels.

Symptoms can include feverish effects such as shivering, excess sweating, muscle stiffness, restlessness, flushed skin, dilated pupils, disorientation, and confusion, as well as high blood pressure, muscle spasms, and diarrhea.

More serious symptoms can include seizures, fainting, arrhythmia, or an abnormal heartbeat, rapid heart rate and high blood pressure. You may experience headaches and migraines, hyperreflexia, or heightened reflexes, 

If you’re on a medication that can improve serotonin, either as its main purpose or as a side effect, or are taking supplements known to spike serotonin output, you may be at risk of developing serotonin syndrome.

This is especially the case if you have just begun taking a new medication, increased dosage of a medication you’re already taking, or taking more than the prescribed amount of a medication. Additional medications, supplements, or illicit drugs can also spike serotonin levels.

These medications, supplements, and substances include:

  • SSRIs
  • monoamine oxidase inhibitors (MAOIs)
  • dextromethorphan
  • many medications prescribed for mental health conditions
  • St. John’s wort
  • SAMe
  • tryptophan
  • amphetamines
  • cocaine
  • MDMA (ecstasy)

There are no specific, singular tests that can fully investigate or diagnose serotonin syndrome, just as there is no specific test for serotonin deficiency. Largely, symptoms and medical history can lead to a fairly solid diagnosis. If you are taking any of the above medicines, supplements, or substances, and are experiencing any of the above symptoms, you may be asked to cut them out or down. If your symptoms go away, your serotonin levels were likely too high and are now back to a healthy range.

However, there are some physical examinations and various additional tests that can help to diagnose serotonin syndrome. These can include brain imaging, blood and urine tests, and spinal taps (lumbar punctures).

Mild cases will be treated as above – cut out anything you’re taking that may be spiking your serotonin levels. However, if the case is more serious, or you’re experiencing serotonin syndrome without taking any of the above medications, supplements, or substances (which is very rare), the doctor may prescribe additional medications. These should treat the symptoms.

Very severe cases may need hospital treatment. However, this is also very rare. Symptoms should usually be able to manage on an outpatient basis and should generally resolve within 2 – 3 days.

If you’re suffering any of the above symptoms, make sure that you consult your doctor immediately. If you’re suffering any of the above symptoms and taking any of the above medications, supplements, or substances, serotonin syndrome is likely. 

Medications and serotonin

We’ve seen that certain medications can interact with serotonin levels, boosting them at least in the blood stream. Serotonin and serotonin receptors are actually quite common targets in the modern pharmaceutical industry and in modern treatment processes. Plenty of health conditions can be managed and improved by managing serotonin levels, as we have seen.

Perhaps most notably, there are a few different forms of antidepressant drugs that inhibit serotonin reabsorption and recycling.

These are mostly selective serotonin reuptake inhibitors, or SSRIs, and are one of the most common forms of depression and anxiety treatments going (think Prozac, or fluoxetine, and the like).

You may also see serotonin-norepinephrine reuptake inhibitors, or SNRIs, and tricyclic antidepressants. Monoamine oxidase inhibitors, another, less common type of antidepressant drug, inhibits enzyme reactions that break down serotonin. 

However, there are also plenty of medications that interact with serotonin without serotonin necessarily being their main target. These include the triptan family of headache drugs, alongside opioid pain relievers and certain common cough suppressants and nausea fighting drugs which include dextromethorphan.

Talk to your doctor

If you suspect that your serotonin levels are suboptimal for any reason, you should consult with your medical provider as soon as possible. As we have seen, serotonin levels can have a profound impact on your mental and physical health and wellbeing. It will be very hard to remain happy and motivated with them too low, and you run several risks if they are too high.

Do note that the link between depression and serotonin is not absolute. The link between serotonin and all of the health concerns mentioned above is not absolute. It is possible to be depressed, or to suffer from many of the above concerns, with your serotonin levels running optimally. The human body is, after all, dizzyingly complex, and we are a long way from coming fully to grips with it.

Don’t simply reach for a serotonin supplement if you want to cheer yourself up a bit.

Your doctor will be able to properly advise you, run the appropriate tests, and monitor your progress safely through any potential treatment plan. If you suffer with depression or anxiety, memory loss, issues with mobility or movement, changes in sleep quality and patterns, in appetite, libido, or digestive health, or any of the above symptoms, talk to your doctor, especially if you’re taking any prescription medications or recreational drugs.

There is a good chance that your serotonin levels are off and an intervention may be needed. Your doctor will be able to properly, more fully advise you.

Serotonin: frequently asked questions

How can you tell that your serotonin levels are low?

You can’t really tell that your serotonin levels are low. Doctors will not run blood tests or anything like that. Rather, you can infer that your levels are low based on symptoms. If you struggle with low mood, poor concentration, low libido, or any of the other signs of serotonin depletion, your serotonin levels are probably low and a doctor will treat you as such.

How can you raise your serotonin levels?

Serotonin levels can be quite drastically impacted by lifestyle factors. If you keep your stress and anxiety levels to a minimum, get plenty of rest, exercise, and sunlight, you should be able to bolster your serotonin output. Couple this with foods and supplements rich in tryptophan and your levels should quickly rise.

What’s the difference between dopamine and serotonin?

Serotonin and dopamine are often spoken about in similar terms. They are both important neurotransmitters intimately involved in various similar processes. Each is associated with mental wellbeing and satisfaction levels. This makes it quite easy to think of them almost synonymously. However, they are not the same – there are some quite distinct differences between the two.

For instance, where serotonin is stored largely in the gut, dopamine is found mostly in the brain. They influence your mood differently, too. Serotonin is responsible for your mood and anxiety levels, whilst dopamine is concerned largely with motivation, reward, and pleasure. Serotonin is targeted by common depression treatment plans, whilst dopamine isn’t. Finally, they both play a role in energy levels, just through different mechanisms. Serotonin helps in sleep and wakefulness regulation whilst dopamine helps you to feel more alert and switched on.

When should you see your doctor about low serotonin output?

You typically won’t go to see a doctor about low serotonin output, though you can and should if you suspect that you’re not producing enough. Rather, explain your symptoms to them if you have been struggling with anything. Depression, anxiety, low libido and so on will often be down to low serotonin levels, and your doctor will take it from there, explaining diagnostic and treatment options.

My final thoughts On Serotonin

Serotonin is an incredibly important neurotransmitter. Maintaining optimal levels – neither too low, as is often the case, nor too high, which is more rarely seen – is key to maintaining long term mental and physical health and wellbeing.

It is central to regulating your mood, stress and anxiety levels, sleep quality, appetite and digestive health, libido, bone health, and even your ability to heal.

If you struggle with any of the symptoms we’ve been through today, speak to your healthcare provider. They will be able to match you up with a good treatment program, likely including a mixture of medication, various therapies, and lifestyle choices geared towards optimising serotonin output.

Your life and wellbeing may well drastically benefit from getting your serotonin levels just right.