Serotonin syndrome (A complete guide)

Serotonin syndrome is a very dangerous condition prompted by an overdose on certain serotonergic drugs.

Here you will learn all about the symptoms, causes, risks, and prevention of serotonin syndrome.

What is serotonin syndrome?

Serotonin syndrome is a condition that is caused by the use of certain medications that cause great amounts of the chemical serotonin to build up in your body.

Serotonin is a chemical that your brain produces which is necessary for both your nerve cells and brain to function.

However, serotonin may cause experiences and symptoms that can range from mild, such as shivering and diarrhea, to severe, such as muscle rigidity, fever and seizures.

If left untreated, severe serotonin syndrome can cause death.

In the event that you increase the dosage of certain medications or introduce another medication or drug into your medicine regimen, there is a possibility that serotonin syndrome could occur.

Furthermore, some illegal drugs and dietary supplements have been found to be associated with causing serotonin syndrome.

Less severe cases of serotonin syndrome stop persisting after a day of terminating taking the medications that may cause you to feel the symptoms of serotonin syndrome.

Additionally, serotonin syndrome can be terminated by taking certain drugs that are known to block serotonin reuptake.

What are the symptoms of serotonin syndrome?

Serotonin syndrome side effects often occur after a few hours of taking a new medicine or drug, or after increasing the amount of a drug that you have already been taking.

Indicators and symptoms of serotonin syndrome include:

  • Agitation or restlessness
  • Confusion
  • Rapid heart rate and high blood pressure
  • Dilated pupils
  • Loss of muscle coordination or twitching muscles
  • Muscle rigidity
  • Heavy sweating
  • Diarrhea
  • Headache
  • Shivering
  • Goosebumps

Very dangerous symptoms of serotonin syndrome are life threatening and it is of the utmost importance that you seek immediate medical attention if you are experiencing any of the following symptoms:  

  • High fever
  • Seizures
  • Irregular heartbeat
  • Unconsciousness

When to see a doctor

If you believe you might have serotonin syndrome after starting a new drug or increasing the dose of a drug you’re already taking, call your doctor immediately or go to the emergency room.

If you have severe or rapidly worsening symptoms, seek emergency treatment immediately.

What are the causes of serotonin syndrome?

The most common cause of serotonin syndrome symptoms is the excessive accumulation of the chemical serotonin in your body. 

Usually, nerve cells in your brain and spinal cord create the chemical serotonin which helps regulate your focus, behavior and body temperature.

Other nerve cells in your body, primarily in your intestines, also produce serotonin.

Serotonin helps to facilitate and moderate your digestive process, blood flow and also your breathing.

Serotonin syndrome often occurs when you combine certain medications together, however it is also possible to acquire serotonin syndrome just by taking a single drug that causes serotonin levels to greatly increase. 

For example, if you take an antidepressant with a migraine helping drug, serotonin syndrome could possibly occur.

It may also occur if you take an antidepressant with an opioid pain medication.

Another cause of serotonin syndrome is intentional overdose of antidepressant medications.

A number of over-the-counter and prescription drugs are associated with serotonin syndrome, most notably antidepressants.

Furthermore ,illicit drugs and dietary supplements are often associated with serotonin syndrome.

The drugs and supplements that could potentially cause serotonin syndrome include:

  • Selective serotonin reuptake inhibitors (SSRIs), antidepressants such as citalopram (Celexa), fluoxetine (Prozac, Sarafem), fluvoxamine, paroxetine (Paxil, Pexeva, Brisdelle) and sertraline (Zoloft)
  • Serotonin and norepinephrine reuptake inhibitors (SNRIs), antidepressants such as duloxetine (Cymbalta, Drizalma Sprinkle) and venlafaxine (Effexor XR)
  • Bupropion (Zyban, Wellbutrin SR, Wellbutrin XL), an antidepressant and tobacco-addiction medication
  • Tricyclic antidepressants, such as amitriptyline and nortriptyline (Pamelor)
  • Monoamine oxidase inhibitors (MAOIs), antidepressants such as isocarboxazid (Marplan) and phenelzine (Nardil)
  • Anti-migraine medications, such as carbamazepine (Tegretol, Carbatrol, others), valproic acid (Depakene) and triptans, which include almotriptan, naratriptan (Amerge) and sumatriptan (Imitrex, Tosymra, others)
  • Pain medications, such as opioid pain medications including codeine, fentanyl (Duragesic, Abstral, others), hydrocodone (Hysingla ER, Zohydro ER), meperidine (Demerol), oxycodone (Oxycontin, Roxicodone, others) and tramadol (Ultram, ConZip)
  • Lithium (Lithobid), a mood stabilizer
  • Illicit drugs, including LSD and amphetamines
  • Herbal supplements, including St. John’s wort, ginseng and nutmeg
  • Over-the-counter cough and cold medications containing dextromethorphan (Delsym)
  • Anti-nausea medications such as granisetron (Sancuso, Sustol), metoclopramide (Reglan), droperidol (Inapsine) and ondansetron (Zofran, Zuplenz)
  • Linezolid (Zyvox), an antibiotic
  • Ritonavir (Norvir), an anti-retroviral medication used to treat HIV

What are the risk factors for developing serotonin syndrome?

While the condition could occur in anyone, certain people are more likely to develop serotonin syndrome due to the drugs and supplements that cause the syndrome.

Serotonin syndrome risk is increased if:

  • You recently began taking or increased the dose of a medication which known to increase serotonin levels
  • You take more than one drug known to increase serotonin levels
  • You take herbal supplements known to increase serotonin levels
  • You use an illicit drug known to increase serotonin levels


Once serotonin levels return to their normal amounts, serotonin syndrome generally doesn’t cause any problems.

However, if left untreated, severe serotonin syndrome can lead to unconsciousness and death.


Your risk of developing serotonin syndrome is increased if you take more than one serotonin-related medication or increase your dose of a serotonin-related medication.

Be sure to talk to your doctor if you or a family member has experienced symptoms after taking a medication.

Also consult with your medical care provider about possible risks in taking any drug you are considering or that they prescribe to you.

Never terminate taking any type of medications without proper medical approval and oversight.

If your doctor prescribes a new medication to you, ensure that he or she is completely aware about all the other medications you’re taking, especially if you receive prescriptions from more than one doctor.

If you and your doctor decide the benefits of combining certain serotonin-level-affecting drugs outweigh the risks, be alert to the possibility of serotonin syndrome.

Who is at risk for developing serotonin syndrome? 

People who are taking selective serotonin reuptake inhibitors (SSRIs) are at particular risk for developing serotonin syndrome.

These medications increase the available serotonin in the brain and serotonin syndrome can result if the levels of serotonin become too high. 

People who have major depressive disorder (MDD), seasonal affective disorder (SAD), or an anxiety disorder may be taking an SSRI and are at risk for developing serotonin syndrome.  

If you suspect you have MDD, SAD, an anxiety disorder, or another related condition, talk to your doctor about taking antidepressants.

In addition, a loved one or friend may reach out to discuss these symptoms with you and point you in the direction of help.

These are debilitating mental health conditions and you should not feel like you have to go through them alone. 

MDD is a mood disorder that causes feelings of worthlessness and loss of interest in daily activities. Common symptoms of MDD are as follows: 

·      Chronic feelings of sadness, tearfulness, emptiness, or hopelessness

·      Loss of interest in activities that once used to bring enjoyment (i.e., sex, hobbies) 

·      Outbursts of anger 

·      Irritability

·      Frustration

·      Issues with sleeping too much or insomnia

·      Lack of energy and fatigue 

·      Changes in eating patterns and weight (i.e., increased appetite and weight gain or reduced appetite and weight loss)

·      Anxiety

·      Agitation

·      Restlessness

·      Slowed speaking, thinking, and movement 

·      Feelings of worthlessness 

·      Ruminating on past failures

·      Feelings of guilt 

·      Trouble concentrating, making proper decisions, and remembering things 

·      Physical problems such as back pain or headaches that cannot be explained by another medical condition 

SAD is a subtype of depression that is heavily related to changes in seasons.

It usually begins at the same time every year and usually occurs during fall and winter months.

If you have any of the following symptoms, you may be diagnosed with SAD: 

·      Feelings of depression most of the day almost every day

·      Low energy

·      Loss of interest in activities that used to bring enjoyment

·      Trouble sleeping, usually oversleeping 

·      Changes in appetite or weight 

·      Feelings of hopelessness, worthlessness, or guilt

·      Feeling agitated or sluggish 

·      Frequent thoughts of death or suicide

In the winter months, people with SAD may frequently oversleep, gain weight due to food cravings high in carbohydrates, or have fatigue and lack of energy.

More rarely, people can suffer from SAD in the spring or summer months.

These patients are likely to experience trouble sleeping (insomnia), reduced appetite and weight loss, and agitation or anxiety. 

Anxiety attacks can be part of an anxiety disorder. Be sure not to confuse normal every day anxiety with an anxiety disorder.

If you are experiencing a problem at work, a big exam coming up, or an important decision, you are probably having a normal anxious reaction to life stressors.

Anxiety disorders, however, are chronic and usually center around irrational fears and worry. 

There are many different types of anxiety disorders such as generalized anxiety disorder (GAD), panic disorder, and social anxiety disorder, to name a few.   

Symptoms of GAD usually include: 

·      Feelings of restlessness or on edge

·      Difficulty concentrating and racing thoughts

·      Muscle tension

·      Irritability

·      Trouble sleeping

·      Difficulty controlling feelings of worry

·      Easily fatigued 

Symptoms of panic attacks, which can be a symptom of panic disorder, include:

·      Heart palpitations or accelerated heart rate 

·      Sweating, trembling, shaking

·      Shortness of breath 

·      Feelings of impending doom 

Phobia-related disorders are another set of anxiety disorders that are characterized by an intense fear or aversion to specific situations or objects.

This fear is usually out of proportion to the actual danger imposed by the situation or object. 

·      Irrational or excessive worry about encountering the feared object or situation 

·      Intentional avoidance of feared object or situation 

·      Intense and immediate anxiety upon exposure to the object or situation 

Specific phobias can be related to situations such as flying or heights, or related to animals such as spiders.

Some people also have phobias of receiving injections or blood.

Agoraphobia is another type of anxiety disorder where people have an intense fear of two or more of the following situations: 

·      Being in open or enclosed spaces

·      Standing in lines

·      Crowded areas

·      Using public transportation

·      Being outside of their home 

People with agoraphobia often avoid these situations out of fear that they will not be able to escape.

Some have an intense fear that they will panic or have other embarrassing symptoms.

In severe cases, people may avoid leaving their house altogether. 

If you suspect you have an anxiety disorder, do NOT start taking any medication from a non-reputable source such as a friend, consult a psychiatrist immediately.

Frequently asked questions (FAQs) about serotonin syndrome:

How do you know if you have serotonin syndrome?

Here are some of the symptoms: agitation or restlessness, confusion, quick heart rate, high blood pressure, dilated pupils, loss of muscle coordination, profuse sweating, diarrhea, headache, shivering, goosebumps, high fever, seizures, irregular heartbeat, unconsciousness.

If you think you may have serotonin syndrome, consult a medical provider immediately.

What does it feel like to have serotonin syndrome?

Gastrointestinal symptoms include diarrhea and vomiting.

Nervous system symptoms include overactive reflexes and muscle spasms, said Su.

Other serotonin syndrome symptoms include high body temperature, sweating, shivering, clumsiness, tremors, and confusion and other mental changes.

How do you get rid of serotonin syndrome?

Benzodiazepine medicines, such as diazepam (Valium) or lorazepam (Ativan) to decrease agitation, seizure-like movements, and muscle stiffness.

Cyproheptadine (Periactin), a drug that blocks serotonin production.

Intravenous (through the vein) fluids.

Withdrawal of medicines that caused the syndrome. 

Can serotonin syndrome kill you?

Serotonin syndrome can be mild, but in rare situations, it can kill you if it is left untreated.

Medications for Anxiety & Depression – A no-nonsense, comprehensive guide to the most common (and not so common) antidepressants and anti-anxiety drugs available

Serotonin Syndrome: Treatments and Resources bertrand jason, Jason Bertrand


Antidepressants: Selecting one that’s right for you. Mayo Clinic. December 31st, 2019. 

How to recognize an anxiety attack. Medical News Today. November 5th, 2018. 

Was this helpful?

Thanks for your feedback!