Serotonin syndrome can happen when there is too much serotonin in the body. It is most often linked to medications, supplements, or substances that raise serotonin levels, especially when more than one is taken at the same time. Severe cases can be life-threatening, so symptoms should be taken seriously.
If you think you may have serotonin syndrome after starting a new medication, increasing a dose, or mixing medications or substances, call your doctor right away or go to the emergency room. If symptoms are severe or getting worse quickly, seek emergency care right away.
What Is Serotonin Syndrome?
Serotonin syndrome, also called serotonin toxicity, happens when serotonin builds up too much in the body. Serotonin is a chemical that helps the brain and body regulate mood, sleep, digestion, body temperature, and other functions.
The body needs serotonin, but too much can become dangerous. This can happen after starting a new medication, raising the dose of a medication, taking too much of a medication, or combining substances that affect serotonin.
Serotonin syndrome can cause mild symptoms, such as nausea or diarrhea, or severe symptoms, such as high fever, seizures, confusion, or fainting. Severe cases need urgent medical care.
How Do You Know if You Have Serotonin Syndrome?
You may have serotonin syndrome if symptoms start soon after taking something that raises serotonin. Symptoms often begin within minutes to hours after taking a serotonin-related medication, starting a new drug, increasing a dose, or combining medications or substances.
Common signs include changes in how you feel mentally, physically, and in your muscles.
Mental and Emotional Symptoms
Serotonin syndrome can affect mood, alertness, and thinking. You may feel unlike yourself or notice a sudden shift after a medication change.
Symptoms may include:
- Agitation
- Restlessness
- Anxiety
- Confusion
- Trouble sleeping
- Hallucinations
- Disorientation
Confusion, delirium, or severe disorientation can be signs of a more serious case and should be treated as urgent.
Body Symptoms
Serotonin syndrome can also affect heart rate, blood pressure, digestion, sweating, and body temperature.
Symptoms may include:
- Fast heartbeat
- High blood pressure
- Diarrhea
- Nausea or vomiting
- Heavy sweating
- Shivering
- Headache
- Dilated pupils
- Increased body temperature
A high fever is a warning sign of severe serotonin syndrome, especially if it happens with confusion, shaking, muscle stiffness, or a racing heart.
Muscle and Movement Symptoms
Muscle symptoms are one of the main clues doctors look for.
Symptoms may include:
- Tremors
- Muscle twitching
- Muscle rigidity
- Shaking
- Loss of coordination
- Overactive reflexes
- Abnormal eye movements
These symptoms can make it hard to walk, stay steady, or control your movements.
When Is Serotonin Syndrome an Emergency?
Serotonin syndrome can become an emergency if symptoms are severe, sudden, or getting worse.
Call 911 or go to the ER right away if you have:
- High fever
- Seizures
- Irregular heartbeat
- Fainting
- Severe confusion
- Loss of consciousness
- Severe muscle stiffness
- Trouble breathing
Mayo Clinic advises emergency treatment for severe or rapidly worsening symptoms. Cleveland Clinic also notes that untreated serotonin syndrome can lead to serious complications, including seizures, trouble breathing, kidney failure, coma, and death.
If you are unsure what to do after taking a medication, supplement, or substance, you can also call Poison Help at 1-800-222-1222 in the U.S. The service is free, confidential, and available 24/7. If someone collapses, has a seizure, has trouble breathing, or cannot wake up, call 911 immediately.
What Causes Serotonin Syndrome?
Serotonin syndrome is usually caused by medications, supplements, or substances that raise serotonin levels. It is more likely when someone takes more than one serotonin-related product at the same time, starts a new medication, increases a dose, or takes too much of a medication.
Medications That May Raise the Risk
Several types of medications can be linked to serotonin syndrome, especially when combined.
These may include:
- Antidepressants like SSRIs, such as fluoxetine, sertraline, paroxetine, citalopram, and escitalopram
- SNRIs, such as venlafaxine, duloxetine, desvenlafaxine, and levomilnacipran
- MAOIs, which are older antidepressants
- Tricyclic antidepressants, such as amitriptyline and nortriptyline
- Migraine medications called triptans
- Some opioid pain medications, including fentanyl and meperidine
- Cough and cold medicines with dextromethorphan
- Linezolid, which is an antibiotic
- Lithium
- Some anti-nausea medications
This list is not complete. Always tell your doctor and pharmacist about every prescription, over-the-counter medicine, supplement, and substance you take.
Supplements and Substances That May Raise the Risk
Some supplements and substances can also affect serotonin.
These may include:
- St. John’s wort
- Ginseng
- Tryptophan
- Ecstasy or MDMA
- LSD
- Cocaine
- Amphetamines
- Methamphetamine
Combining these with antidepressants or other serotonin-related medications can increase risk.
What Should You Do if You Think You Have Serotonin Syndrome?
If you think you may have serotonin syndrome, treat it as a medical concern rather than trying to manage it alone.
1. Get Medical Advice Right Away
Call your prescribing doctor, pharmacist, or Poison Help if symptoms are mild and you are not sure what is happening. Go to the ER or call 911 if symptoms are severe, sudden, or getting worse.
This is especially important if symptoms started after:
- Taking a new medication
- Increasing a medication dose
- Mixing antidepressants with other medications
- Taking cough medicine with dextromethorphan
- Using opioids, stimulants, or recreational substances
- Taking herbal supplements with prescription medication
2. Do Not Change Medications Without Guidance
Do not stop taking prescription medication or change your dose without talking to a healthcare provider first. Stopping some medications suddenly can cause withdrawal-like symptoms, mood changes, or other health risks..
If a provider thinks serotonin syndrome is possible, they may tell you to stop or change the medication causing the problem. That decision should come from a medical professional who understands your symptoms, medications, and health history.
3. Bring a Full Medication List
A clear medication list can help doctors treat you faster.
Include:
- Prescription medications
- Over-the-counter medicines
- Vitamins
- Supplements
- Herbal products
- Recreational substances
- Recent dose changes
- The time you took each substance
Doctors diagnose serotonin syndrome by reviewing symptoms, medical history, and medication use. There is no single test that confirms it, so this information matters.
4. Be Honest About Substance Use
It can feel uncomfortable to talk about drug use, alcohol use, or taking more medication than prescribed. Still, honesty can protect your health.
Some substances can raise serotonin or interact with medications. Your care team needs accurate information so they can treat the real problem and avoid unsafe medication combinations.
How Is Serotonin Syndrome Treated?
Treatment depends on how severe the symptoms are.
Mild symptoms may improve after a doctor changes or stops the medication causing the problem.
Moderate symptoms may need hospital monitoring.
Severe serotonin syndrome may require intensive care, especially if the person has a high fever, seizures, unstable blood pressure, or trouble breathing.
Treatment may include:
- IV fluids for dehydration and fever
- Oxygen to support breathing
- Medicine to calm agitation or muscle stiffness
- Medicine to control heart rate or blood pressure
- A serotonin-blocking medication, such as cyproheptadine
- Breathing support in severe cases
Many mild cases improve within 24 to 72 hours with proper treatment, but symptoms linked to some antidepressants may take longer because those medications can stay in the body for weeks.
Can Serotonin Syndrome Go Away on Its Own?
Mild cases may improve after the medication causing the problem is stopped or changed, but this should happen under medical guidance. Mayo Clinic notes that mild cases often improve within 24 to 72 hours after stopping medications that increase serotonin, but some cases need medications that block serotonin or hospital care.
Do not wait it out if symptoms are severe, unusual, or getting worse. Serotonin syndrome can become dangerous without treatment.
How Can You Tell if it’s Serotonin Syndrome vs. Anxiety?
Serotonin syndrome and anxiety can feel similar at first. Both can cause restlessness, sweating, a fast heartbeat, trouble sleeping, nausea, and feeling on edge.
The biggest difference is the trigger. Anxiety may happen during stress, panic, or emotional overwhelm. Serotonin syndrome is more likely when symptoms start soon after:
- Starting a new medication
- Increasing a medication dose
- Taking too much medication
- Mixing medications, supplements, or substances that affect serotonin
Watch for Symptoms That Feel Different
As mentioned previously, serotonin syndrome can also cause symptoms that are not typical of anxiety, such as diarrhea, high fever, muscle stiffness, overactive reflexes, confusion, poor coordination, or abnormal eye movements.
Anxiety can feel intense, but it does not usually cause a high fever, severe muscle rigidity, or sudden changes in reflexes or coordination.
Get Medical Guidance if You’re Unsure
You do not have to figure out the difference by yourself. If symptoms start after a medication change, supplement use, or substance use, call your doctor, pharmacist, or Poison Help at 1-800-222-1222.
As mentioned earlier, call 911 or go to the emergency room if symptoms are severe, getting worse quickly, or include high fever, seizures, fainting, severe confusion, trouble breathing, or loss of consciousness.
How to Lower the Risk of Serotonin Syndrome
You may not be able to remove every risk, but you can lower the chance of dangerous interactions. Here’s a summary of some of the things we’ve discussed in this article:
- Keep an Updated Medication List: Write down every medication, supplement, and over-the-counter product you take.
- Read Medication Labels: Some cough, cold, migraine, pain, and mood medications can interact with antidepressants or other serotonin-related medications.
- Ask Before Adding Supplements: Natural products can still affect the body. Tell your doctor about supplements before taking them with antidepressants or other medications.
- Avoid Substances: MDMA, cocaine, LSD, amphetamines, and methamphetamine can increase risk when used with antidepressants or other serotonin-related medications.
FAQs About Serotonin Syndrome
How fast does serotonin syndrome start?
Symptoms often begin within minutes to hours after taking a medication or substance that raises serotonin. They may also start after increasing a dose or combining medications.
What are the first signs of serotonin syndrome?
Early signs may include agitation, restlessness, diarrhea, nausea, sweating, shivering, fast heartbeat, high blood pressure, tremors, twitching, or trouble with coordination.
What does mild serotonin syndrome feel like?
Mild symptoms can include nervousness, nausea, vomiting, diarrhea, dilated pupils, shakiness, sweating, shivering, and restlessness. Mild symptoms still deserve medical guidance, especially after a medication change.
What are severe serotonin syndrome symptoms?
Severe symptoms may include high fever, seizures, irregular heartbeat, fainting, unconsciousness, severe confusion, or very stiff muscles. These symptoms need emergency care.
Can serotonin syndrome happen from one medication?
Yes, it can happen from one medication in some cases, but it is more common when people combine medications or substances that affect serotonin. It can also happen after a dose increase or overdose.
Should I stop my antidepressant if I think I have serotonin syndrome?
Do not stop or change your medication without medical guidance unless emergency providers tell you to do so. Call your doctor right away, call Poison Help, or go to the ER if symptoms are severe or getting worse.
Get Support for Medication or Substance Use Concerns
Serotonin syndrome can feel scary, especially when symptoms start after a medication change, substance use, or mixing more than one medication.
If symptoms are severe, sudden, or getting worse, call 911 or go to the emergency room right away. You can also call Poison Help at 1-800-222-1222 for guidance in the U.S.
After the immediate medical concern is addressed, ongoing support may be needed if prescription medication misuse, substance use, or relapse risk played a role. At Northpoint Recovery, we help people take the next step with compassionate, structured drug addiction treatment.
Depending on your needs, care may include medical detox, inpatient treatment, outpatient treatment, virtual outpatient care, and aftercare planning.
Our team can help you understand what level of care may be right for you, whether you need a safe place to detox, a more structured treatment setting, or continued support while managing daily responsibilities.
Contact us today to learn more about our drug addiction treatment programs – we’re here to help you or a loved one heal and find lasting recovery.
