What Is Serotonin Syndrome?

Medically Reviewed by Jabeen Begum, MD on September 22, 2023
8 min read

Serotonin syndrome can happen when your body has too much of a chemical called serotonin, usually because of a medication or a combination of medications.

What is serotonin?

Your body makes serotonin, or 5-hydroxytryptamine (5-HT), to help your brain cells and other nervous system cells communicate with each other. This chemical plays many different roles in your body. It affects your sleep, memory, ability to learn, happiness, body temperature, hunger, and sexual behavior.

Most of your body's serotonin is in your gut; only around 10% is made in your brain. Serotonin is created from an essential amino acid called tryptophan. You can only get essential amino acids from the foods you eat, as your body can't make them on its own.

Researchers think a lack of serotonin in your brain may play a role in depression. However, too much of it can lead to extreme nerve cell activity and dangerous symptoms.

Serotonin syndrome vs. NMS

Neuroleptic malignant syndrome (NMS) is similar to serotonin syndrome. This condition is rare but very serious. If it's not treated quickly, it can lead to death. But most people recover fully after treatment.

Like serotonin syndrome, NMS can happen due to certain medications. Medications that tend to cause this issue are called neuroleptics or antipsychotics. These treat disorders such as schizophrenia and other similar conditions.

Less commonly, medications that treat or prevent vomiting might also cause NMS.

The condition can also happen in people who have Parkinson's disease. Usually, it happens when you stop taking or lower a medication dose too quickly.

The symptoms of NMS are similar to serotonin syndrome symptoms. They include:

  • Very stiff muscles
  • Tremors (when parts of your body shake)
  • Trouble talking or swallowing
  • Changes in your behavior or thinking
  • Confusion or edginess
  • Not being able to talk or move
  • Fever
  • Changes in your heart rate
  • High blood pressure
  • Breathing faster than normal
  • Sweating more than usual

In severe cases of NMS, you might have other serious symptoms, such as:

  • Heart issues
  • Harmful blood clots
  • Kidney failure
  • Infection

To figure out if you have serotonin syndrome or NMS, your doctor will carefully look at your medication history and perform different tests.

Serotonin syndrome symptoms often begin hours after you take a new medication that affects your serotonin levels or after you raise your dose of a current drug. Symptoms may include:

In severe cases, serotonin syndrome can be life-threatening. Call 911 or go to the emergency room if you have any of these symptoms:

When do serotonin syndrome symptoms show up?

Symptoms of serotonin syndrome tend to show up quickly within 24 hours of taking a medication that causes the condition. Within 1 hour of taking a medication, 30% of people with the condition will develop symptoms. Within 6 hours, 60% of people with the condition will develop symptoms.

How long does serotonin syndrome last?

Serotonin syndrome will usually last for 24 to 72 hours in most people if the condition is discovered and treated properly.

Most deaths happen within the first 24 hours of the onset of the condition. This mostly happens when a person takes multiple medications.

Antidepressants and serotonin syndrome

Usually, medications cause serotonin syndrome, especially certain antidepressants. You might be at higher risk if you take two or more drugs and/or supplements that affect your serotonin levels.

Selective serotonin reuptake inhibitors (SSRIs) are the most commonly prescribed class of antidepressants. They work by raising your serotonin levels. These drugs include:

Other antidepressants that can lead to serotonin syndrome include:

Antidepressants that affect multiple serotonin receptors include vilazodone (Viibryd) and vortioxetine (Trintellix).

Other drugs that can cause serotonin syndrome

Some other prescription and over-the-counter drugs that can raise your serotonin levels, either alone or when you take them together, include:

Dietary supplements . These include St. John's wort, ginseng, Syrian rue, nutmeg, and tryptophan. These can cause serotonin syndrome when you take them with antidepressants.

The FDA has asked drug makers to add warning labels about the risk of serotonin syndrome. If you have questions about a medication, check the label or ask your doctor. Don't stop taking any medication before talking to your doctor.

Recreational drugs that can cause serotonin syndrome

Some recreational drugs, such as LSD, cocaine , ecstasy, amphetamines, fentanyl, and methamphetamines can also cause serotonin syndrome if you take them with antidepressants.

Without treatment, serotonin syndrome can cause:

No single test can tell your doctor that you have serotonin syndrome. Instead, they’ll ask about your medical history—including your use of medications, supplements, and recreational drugs—and do a physical exam. It's important to be honest with your doctor, even when it comes to taking illegal drugs. They won't get you into any trouble for using them. They care about helping you, not judging you.

They may order lab tests to rule out other health conditions that can look like serotonin syndrome, such as tetanus, sepsis, encephalitis, or heatstroke. These tests may include:

  • Ones that look at how well your body functions
  • Blood and pee tests to measure the levels of drugs you're using
  • Ones that look for signs of infection (such as a spinal tap)
  • Chest X-ray or CT scan to look for any complications or rule out other disorders that have similar symptoms

Removing the drug that caused your serotonin syndrome is crucial. You’ll probably feel better within a day of stopping the medication, although some drugs can take longer to leave your system.

Your treatment will depend on how severe your symptoms are.

For mild symptoms. If your symptoms don't go away fast, your doctor might give you a serotonin blocker. This stops your body from making serotonin.

For moderate symptoms. Your doctor might want to watch you in the hospital for at least 24 hours to make sure that your symptoms are getting better with treatment.

For severe symptoms. You may have to go to an intensive care unit (ICU). Here, your doctors can closely watch your body and organ functions.

Your doctor will give you different treatments based on your symptoms. These might include:

Serotonin-production blocking agents. Drugs such as cyproheptadine (Periactin ) can help block serotonin production.

Muscle relaxants. Benzodiazepines can help control edginess, muscle stiffness, and seizures. These include drugs such as diazepam (Diastat, Valium) and lorazepam (Ativan).

Drugs that control your heart rate and blood pressure. These can help lower your high heart rate or high blood pressure. They include esmolol (Brevibloc) and nitroprusside (Nitropress).

If your blood pressure is too low, your doctor might have you take other drugs such as phenylephrine (Vazculep) or epinephrine (Adrenalin, Epipen).

Oxygen and intravenous (IV) fluids. Extra oxygen can help keep the oxygen levels in your blood normal. IV fluids can treat dehydration and fever.

A breathing tube and machine with medication to paralyze your muscles. Your doctor may give you this treatment if you have a high fever.


Be sure your doctor knows about all the prescription medications, over-the-counter drugs, supplements, herbs, and illegal drugs you take and any reactions you have, especially if you get prescriptions from more than one place.

If you use more than one drug that affects your serotonin levels, know the symptoms of serotonin syndrome so you can watch for them.

Make sure that you read all of the warnings on your drug's packaging or the informational packet that comes with them. These will let you know if there's any risk of serotonin syndrome.

If you want to stop taking a medication, don't do so until you've asked your doctor about the best way.

If you take an antidepressant as well as a triptan for headaches, make sure your doctor keeps a close watch on you. This is especially true for SSRIs and SNRIs. Your risk of serotonin syndrome is usually very small, but it's always better to be on the safe side. If you notice any symptoms, call your doctor as soon as possible. 

  • Serotonin syndrome happens when your body has too much of a chemical called serotonin, usually because of a medication or a combination of medications.
  • Symptoms can include confusion, edginess, restlessness, headache, and more. They usually show up within 24 hours of taking a medication that causes serotonin syndrome.
  • While it can be fatal, serotonin syndrome is usually curable.
  • Your treatment depends on how bad your symptoms are.

Do I have serotonin syndrome or anxiety?

Cases of serotonin syndrome with mild symptoms, such as tremors or restlessness, might be confused with anxiety. While there are many different symptoms of serotonin syndrome that don't happen with anxiety, it's best to see your doctor if you're concerned.

Does Adderall cause serotonin syndrome?

As Adderall is an amphetamine, misusing it or combining it with other drugs listed above can lead to serotonin syndrome.