Serotonin Syndrome: What You Need to Know If You Take SSRIs

Serotonin is a chemical that affects mood and how the brain responds to things like fear, anxiety, and stress. Many medications increase serotonin levels, including some commonly prescribed for nausea and pain. 

Serotonin syndrome happens when serotonin levels are too high in your body. While many cases of serotonin syndrome are mild, severe cases can be life-threatening. If you or a loved one takes medications that can cause serotonin syndrome, it can be helpful to know what to look out for. 

What is serotonin syndrome?

Serotonin syndrome, also called serotonin toxicity, is a condition caused by medications that increase serotonin levels in your body. It happens when your serotonin levels get too high. It’s not clear how many people get serotonin syndrome because most people with serotonin syndrome have mild symptoms and often don’t seek care. 

Serotonin syndrome symptoms

Serotonin symptoms are caused by too much serotonin in your brain and body. This can cause many different symptoms, like sweating, fever, and confusion. Symptoms range from subtle and mild to severe or even life-threatening. 

Here’s what to look out for:

• Sweating

• Shivering

• Tremor 

• Fast heartbeat

• Feeling anxious or restless

• Nausea and vomiting

• Diarrhea

• Confusion

• Agitation

• Fever

• High blood pressure

• Poor coordination

• Involuntary movement

• Muscle spasms or stiffness

• Unusual eye movements

• Hallucinations

• Seizures

• Loss of consciousness 

Symptoms can show up within minutes of taking the medication. Other times they take hours to appear. Most of the time, symptoms will begin within the first 24 hours after taking the medication.  

If you have serious symptoms — or they seem to be getting worse — you should go to the emergency room or talk with a healthcare provider right away.  

7 medications and supplements that cause serotonin syndrome

Serotonin syndrome is rare. But the truth is: Any medication that affects serotonin can potentially cause serotonin syndrome. 

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It’s most common with selective serotonin reuptake inhibitors (SSRIs) and selective serotonin-norepinephrine reuptake inhibitors (SNRIs) — mainly because these medications are widely used. 

Other medications can cause serotonin syndrome, too. But, remember that taking any one of these medications on its own and at the recommended dose is unlikely to be a problem. Most cases of serotonin syndrome happen when people take two or more medications that affect serotonin at the same time. 

Here’s a (nonexhaustive) list of seven common medications and supplements that can cause serotonin syndrome.  

1. Antidepressants

Antidepressants are the most common medications that cause serotonin syndrome. 

Monoamine oxidase inhibitors (MAOIs) aren’t used much anymore to treat depression, but they’re the most likely to cause serotonin syndrome. MAOIs include: 

• Isocarboxazid

• Phenelzine

• Selegiline

• Tranylcypromine

SSRIs and SNRIs are much more commonly prescribed to treat depression and anxiety. These medications are less likely to cause serotonin syndrome, but it’s possible, especially in people taking high doses in combination with other medications or supplements that release serotonin. 

Common examples of SSRIs and SNRIs include:

• Citalopram (Celexa)

• Desvenlafaxine (Pristiq)

• Duloxetine (Cymbalta)

• Escitalopram (Lexapro)

• Fluoxetine (Prozac)

• Levomilnacipran (Fetzima)

• Paroxetine (Paxil)

• Sertraline (Zoloft)

• Venlafaxine (Effexor)

• Vortioxetine (Trintellix)

• Vilazodone (Viibryd)

2. Herbal supplements

Some people use supplements to treat depression and mood disorders. Taking certain supplements along with prescription antidepressants can cause serotonin syndrome. Supplements that affect serotonin include:

• St. John’s wort

• I-tryptophan

• Ginseng

• Nutmeg

3. Antibiotics, antifungals, and antivirals

Antimicrobials (medications that kill germs) can cause serotonin syndrome when used by people who are also taking an SSRI or SNRI. Be careful with antibiotics, antifungals, and antiviral medications, such as:

• Linezolid

• Isoniazid

• Ciprofloxacin

• Fluconazole

• Ritonavir

4. Pain medications

People taking SSRIs and certain pain medications can also develop serotonin syndrome. Pain medications that increase serotonin levels in the brain include:

• Tramadol

• Methadone

• Meperidine

• Fentanyl 

5. Antinausea medications

Antinausea medications can also increase serotonin levels. People taking SSRI/SNRIs should be careful when using:

• Ondansetron

• Granisteron

6. Migraine medications

Medications called triptans, like sumatriptan and zolmitriptan, are used to treat migraine headaches. They can cause serotonin syndrome when taken with SSRI/SNRIs. 

In 2006, the FDA warned that combining these two types of medications could cause severe serotonin syndrome. But in a large 2018 data review, the number of people who were prescribed triptans and an SSRI/SNRI and ended up with serotonin syndrome (either actual or suspected) was very low — fewer than 1 in 1,000.    

Over-the-counter medications

Two over-the-counter (OTC) medications that raise serotonin levels in the brain are:

• Dextromethorphan 

• Chlorpheniramine 

Nearly all of the dextromethorphan-related serotonin syndrome cases happened because people took dextromethorphan and another serotonin-releasing medication.  

How is serotonin syndrome diagnosed?

Serotonin syndrome is a clinical diagnosis. This means the diagnosis is based on your symptoms and what a healthcare provider observes. There aren’t any blood tests or scans that can confirm the diagnosis of serotonin syndrome. 

Since people can have a wide range of symptoms, healthcare providers sometimes use tools to help determine if someone is having mild or severe symptoms. One tool healthcare providers use is called the Hunter Serotonin Toxicity Criteria (HSTC). 

Can serotonin syndrome go away naturally?

Possibly. If you stop taking the medication that’s causing serotonin syndrome, your symptoms will often go away on their own after 24 to 72 hours — especially if you only have a mild case. You should stay in touch with your healthcare providers, but it’s possible you won’t need any other treatment. 

On the other hand, people with moderate to severe symptoms might need to have additional treatment (more on these below). When in doubt, talk with your healthcare provider. They can help you understand whether it’s safe for you to manage your symptoms at home, or if you should seek medical care. 

Serotonin syndrome treatments

The first treatment for serotonin syndrome is to stop taking any medication that increases serotonin activity in your body. But be aware: Stopping certain types of medications suddenly (like SSRI/SNRIs) can cause other symptoms, too. That’s why it’s important to check in with your healthcare provider before you make any changes.  

In some cases, people with serotonin syndrome will need to go to the hospital for treatment. Treatment may include: 

• Intravenous (IV) fluids

• Oxygen therapy

• Medications including benzodiazepines and cyproheptadine that help counteract the effects of excess serotonin

These treatments can help your symptoms get better, and to minimize the effects of serotonin in your body. Treatment is important because severe cases of serotonin syndrome are a medical emergency and can occasionally cause death.

How long does serotonin syndrome last?

It’s hard to say. Most of the time, serotonin syndrome will get better within 1 to 2 days after you stop taking the medication that caused it. 

But sometimes, it can take longer for serotonin syndrome to go away — especially if your symptoms were caused by a long-acting medication like fluoxetine or selegiline. It can also take longer to recover if you have a severe case of serotonin syndrome. In these situations, your symptoms can continue for days or even weeks. 

How can I prevent serotonin syndrome?

If you take medications that affect serotonin, make sure you:

• Always point this out to your prescriber and pharmacist. 

• Avoid taking more than one medication that affects serotonin at a time — unless directed to do so by your doctor. 

• Use prescription medications only as prescribed by your healthcare provider, and avoid taking extra doses.

• Check with your healthcare provider before starting OTC medications or supplements to make sure they don’t increase serotonin levels. 

Why trust our experts?

Written by:

Sameer Hassamal, MD

Sameer Hassamal is an assistant professor of psychiatry at California University of Sciences and Medicine and Arrowhead Regional Medical Center. He is board certified in adult psychiatry, addiction psychiatry, and brain injury medicine by the American Board of Psychiatry and Neurology.

Edited by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. An experienced and dedicated pulmonologist and hospitalist, she spent a decade practicing and teaching clinical medicine at academic hospitals throughout London before transitioning to a career in health education and health technology.

Reviewed by:

Sarah Gupta, MD

Sarah Gupta, MD, is a licensed physician with a special interest in mental health, sex and gender, eating disorders, and the human microbiome. She is currently board certified by the American Board of Psychiatry and Neurology.

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