Serotonin: So Much More Than Just a Mood Booster

Serotonin is a chemical that helps communication between nerves. It’s most well known for its role in helping to regulate mood. That’s because medications that increase serotonin levels in the brain improve a wide range of mental health disorders, including depression and anxiety. 

But the role of serotonin in mood is complex. Beyond mood, serotonin is a key player in many other processes throughout the brain and body, like memory, digestion, sleep, sex drive — and much more. Scientists still don’t fully understand exactly how serotonin regulates these processes. But, like most things in life, having the right balance seems like it might be connected to mental and physical health. 

What is serotonin?

Serotonin, also known as 5-hydroxytryptamine (5-HT), is a neurotransmitter, a type of chemical. This means that it helps transmit signals between nerves. Most serotonin is made in the digestive tract, but it can be found throughout the body. 

How is serotonin made in the body?

Serotonin is made in the body from tryptophan, an amino acid. You get tryptophan from foods such as:

• Eggs

• Cheese

• Fatty fish (like salmon and tuna)

• Beans (such as chickpeas and kidney beans)

• Meat (such as chicken and turkey) 

• Nuts and seeds

• Soybeans

Your body can’t make tryptophan on its own, so you have to get it from food sources.

What does serotonin do in the body?

Serotonin is important to many bodily functions. In fact, you may be surprised just how diverse serotonin’s reach is. Serotonin plays a role in regulating processes that involve:

• Emotion and mood

• Memory and concentration

• Bowel movements

• Nausea

• Bone health and strength

• Blood clotting

• Sleep

• Libido

• Fertility and pregnancy (blood flow to the uterus and uterine contractions)

What happens if you don’t have enough serotonin?

It’s not clear. For many years, there’s been a theory that low serotonin is connected to mental health conditions, like depression and anxiety. Why? Because many medications (like SSRIs) that treat these conditions work by boosting serotonin activity in your brain. But in reality, there’s no convincing evidence that this is true — at least for depression. 

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At the same time, experts know that serotonin is important for your body and brain. Researchers are studying whether low serotonin could be connected to conditions, including:

• Anxiety

• ADHD

• Autism

• Obesity

• Learning and memory problems

• Alzheimer’s disease

• Irritable bowel syndrome

• High sex drive 

• Migraines

• Fibromyalgia

If you have one of these conditions, it’s possible that increasing the serotonin activity in your body may help. Options include lifestyle changes, medications, or supplements.  

How to increase serotonin levels

You may be able to increase serotonin naturally. Options include:

• Soaking in sunlight

• Exercising regularly

• Eating foods that contain tryptophan

• Meditating

What medications and supplements increase serotonin levels?

Many medications raise blood serotonin levels in the body. Among the long list, a couple of common ones are antidepressant and antianxiety medications.

Medications that increase serotonin levels and activity in the body include the following groups of medications: 

• SSRIs (selective serotonin reuptake inhibitors) are a first-choice treatment for depression and anxiety. Examples include citalopram (Celexa), escitalopram (Lexapro), fluoxetine (Prozac), paroxetine (Paxil), and sertraline (Zoloft). 

• SNRIs (serotonin and norepinephrine reuptake inhibitors) are also common treatments for mood symptoms. Examples include desvenlafaxine (Pristiq), duloxetine (Cymbalta), and venlafaxine (Effexor). 

• Tricyclic antidepressants (TCAs) are older medications for anxiety or depression that can be effective for some people. Examples include amitriptyline, desipramine (Norpramin), doxepin, and nortriptyline (Pamelor).  

• MAOIs (monoamine oxidase inhibitors) include isocarboxazid, phenelzine, and selegiline.

• Antibiotics, antifungals, and antiviral medications include linezolid, isoniazid, ciprofloxacin, fluconazole, and ritonavir.

• Pain medications include tramadol, methadone, and fentanyl. 

• Antinausea medications include ondansetron (Zofran) and granisetron.

• Migraine medications in the triptan class include sumatriptan and zolmitriptan. 

• Antihistamines include dextromethorphan and chlorpheniramine. 

Herbal supplements can also increase serotonin levels, like St. John’s wort and ginseng. But remember: Only use supplements with a healthcare provider’s guidance.

Can you take serotonin as a supplement?

No, experts do not currently recommend any serotonin supplements. Scientists are studying some that may affect serotonin levels, including 5-hydroxytryptophan (5-HTP). But more studies are needed before we know if it works — and if it’s safe. 

It’s important to talk with your healthcare provider about the best treatment for you, including medications, psychotherapy, and possibly supplements. 

What happens if you have too much serotonin?

It’s possible to have too much serotonin. Serotonin has many positive effects throughout the body, but you can have too much of a “good thing.” Excess serotonin can cause you to become very unwell.

Sometimes a tumor (carcinoid syndrome) can cause high levels of serotonin. Carcinoid syndrome causes symptoms like diarrhea, abdominal cramping, and flushed skin. This is rare and usually related to a tumor in the lungs or gastrointestinal tract.

Serotonin syndrome is more common, and it occurs when you have abnormally high levels of serotonin from taking too many medications that increase serotonin levels. 

What is serotonin syndrome?

Serotonin syndrome is when serotonin levels are too high in your body. This can be serious and life-threatening. Usually the cause is taking multiple medications that raise serotonin levels (see the list above).

Symptoms of serotonin syndrome are hard to miss. See a healthcare provider right away if you begin to experience these symptoms: 

• Anxiety or restlessness

• Diarrhea

• Vomiting

• Sweating

• Shakes or trembles

• Confusion

• Muscle spasms

• Fast or irregular heart beat

• Fast, back-and-forth eye movements

• Fever

• Seizures

How do you diagnose issues related to serotonin?

If you’re experiencing symptoms that might be related to high or low levels of serotonin, it’s important to talk with your healthcare provider and get an evaluation. This may include blood tests to check for other causes of your symptoms or imaging studies that can look for serotonin-secreting tumors (carcinoid syndrome).

Can you measure serotonin levels?

Yes, you can measure blood serotonin levels. But these levels won’t represent serotonin levels in other parts of the body, like the brain. The best way to check serotonin levels depends on the possible problems. 

For example, if you’re concerned about a serotonin-producing tumor or cancer, such as carcinoid syndrome, it may help to test serotonin levels in the blood and/or urine. On the other hand, providers diagnose serotonin syndrome based on symptoms and history — not a blood test. 

Why trust our experts?

Written by:

Christina Palmer, MD

Christina Palmer, MD, is a board-certified family physician with a focus on chronic care management, women’s health, and mental health. She’s the co-author of “Open Heart: When Open-Heart Surgery Becomes Your Best Option.”.

Edited by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. A pulmonologist and hospitalist, she practiced and taught clinical medicine at hospitals in London for a decade before entering a career in health education and technology.

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