K2/Spice Symptoms, Signs and Side Effects

Last Updated: May 30, 2023

Editorial Policy | Research Policy

K2 and spice are two of the most popular versions of synthetic cannabinoids. Synthetic cannabinoids are sometimes called synthetic marijuana, as they both interact with cannabinoid receptors in the brain. However, synthetic cannabinoids are chemically and pharmacologically distinct from marijuana.

Many synthetic cannabinoids are frequently laced with potentially lethal chemicals. These chemicals include rat poison (superwarfarins) and fentanyl, which is strongly associated with the recent rise in opioid-related deaths. Discover the symptoms and side effects of using spice/K2 and when to seek help.

Short-Term Side Effects

People use synthetic cannabinoids for a perceived positive experience. Many of the psychological effects are seemingly positive and include euphoria and relaxation. Some people enjoy the feeling of altered perception or a sense of detachment from reality, but these sensations can also be very unnerving. Hallucinations are sometimes reported.

Additional short-term side effects of spice/K2 include:

  • Confusion
  • Paranoia
  • Fear
  • Sleep disturbances
  • Nausea or vomiting
  • Dizziness
  • Rapid heart rate
  • Poor coordination
  • Headaches
  • Appetite changes
  • Diarrhea

Seizures, respiratory depression, stroke and heart attack are signs of acute toxicity and represent a medical emergency. In addition, different brands and batches may cause different short-term side effects.

Long-Term Side Effects

The long-term side effects of K2 and spice use remain unclear. Information about long-term effects is mainly derived from case reports of people who went to emergency services. One case report describes a K2 user who was found unresponsive by his roommate. When he got to the emergency department, it was determined that he had suffered a stroke, heart failure, heart attack, respiratory failure and multi-organ failure. Each of these can cause negative long-term outcomes. When they occur simultaneously, the odds of complete recovery are poor. There are other case reports of people who have used synthetic cannabinoids developing one or more of these conditions.

The effects of synthetic cannabinoids are likely to be quite different depending on what they are laced with. For example, a recent incident in Illinois caused more than 150 people who had used a synthetic cannabinoid product to go to the hospital. They were bleeding from “every orifice,” including ears and eyes. The K2 drug they consumed was laced with superwarfarin, a potent anticoagulant that is normally used in rat poison. Many of those individuals have long-term negative consequences as a result of K2 use, but the actual culprit was superwarfarin. This does not negate the very real dangers that may be associated with synthetic cannabinoids. Instead, it illustrates the importance of avoiding all synthetic cannabinoids. These are unregulated drugs that could have any number of dangerous or even lethal chemicals in them.

Physical Side Effects

Reported physical side effects of synthetic cannabinoid use include:

  • Headache
  • Nausea
  • Vomiting
  • Dizziness
  • Inability to fully empty the bladder
  • Rapid heart rate
  • Difficulty breathing
  • Unconsciousness
  • Seizures
  • Heart attack
  • Stroke
  • Death

Behavioral Side Effects

Commonly reported behavioral side effects of K2 or spice use include:

  • Euphoria
  • Elevated mood
  • Feelings
  • Altered perception or distorted reality
  • Hallucinations
  • Anxiety
  • Restlessness
  • Paranoia
  • Sense of detachment from reality

These symptoms can lead to erratic behavior, including extreme violence or suicide attempts. There are a number of reports of people killing themselves or others while they are high on K2 or spice.

K2/Spice Overdose Signs

Spice and K2 overdose symptoms overlap with signs and symptoms associated with the high. Overdose symptoms include:

  • Vomiting
  • Rapid heartbeat
  • Difficulty breathing
  • Unconsciousness
  • Seizures
  • Stroke
  • Heart attack
  • Erratic behavior

If you are concerned that you or someone else has overdosed on any synthetic cannabinoid product, call 911 immediately.

How to Get Off K2/Spice

Dependence, addiction and withdrawal associated with synthetic cannabinoids is still an area of active research. However, preliminary evidence indicates that regular use of K2 or spice can lead to uncomfortable or debilitating withdrawal symptoms. Treatment for withdrawal and addiction can include:

  • Detox: K2/spice detox and withdrawal are associated with physical and psychological symptoms. Supportive care may be enough during detox, but many patients require medication. The most common drugs that are used to reduce withdrawal symptoms are benzodiazepines, barbiturates and antipsychotics.
  • Residential: Patients who go through medically supervised detox should usually transition into a residential rehab program. Early days of recovery can be especially difficult, and avoiding triggers and relapse is important. Residential rehab provides 24/7 access to medical professionals who can answer questions or address concerns.
  • Outpatient: Residential clients generally transition to an intensive outpatient program. This ensures that they continue to receive the support and supervision needed for maintaining sobriety. People with milder dependence disorders may find that starting in an outpatient program is sufficient. There are several levels of outpatient programs, ranging from daily programs to weekly or bi-weekly sessions. Consult with an accredited rehab center to discuss which program is appropriate for you.
  • Dual diagnosis: Many substance use disorders are caused by undiagnosed mental health illnesses or past emotional trauma. In a recent study on synthetic cannabinoid addiction, several participants had co-occurring psychiatric disorders. These disorders were depression, schizophrenia, ADHD and bipolar disorder. For people with undiagnosed mental health issues, rehab facilities that provide dual diagnosis treatment can be life-changing.

Key Points: K2/Spice Symptoms & Side Effects

Important points to remember about synthetic cannabinoids include:

  • Many people believe that K2 and spice are safe alternatives to marijuana. However,  K2 and spice are often associated with adverse effects
  • Synthetic cannabinoids are often laced with lethal chemicals, such as superwarfarin and fentanyl
  • Physical side effects of spice/K2 include nausea, vomiting, dizziness, rapid heart rate, difficulty breathing, unconsciousness, seizures, heart attack and stroke
  • Psychological side effects of spice include euphoria, restlessness, anxiety, paranoia, a distorted or detached sense of reality, and paranoia. These side effects can translate into erratic or violent behavior.
  • A growing body of evidence supports that K2 and spice are addictive and that withdrawal symptoms are uncomfortable, even debilitating
  • Medically supervised detox is beneficial for chronic spice users, and medicine can help with severe withdrawal symptoms

Synthetic cannabinoids are dangerous drugs that can cause serious adverse effects. If you or a loved one is struggling with synthetic cannabinoid use, The Recovery Village Ridgefield can help. Contact us today to speak with one of our experts.


Our Recovery Advocates are ready to answer your questions about addiction treatment and help you start your recovery.

Call Now

    See if your insurance will cover treatment

    All form submissions are 100% confidential.


    National Institute on Drug Abuse. “Synthetic Cannabinoids (K2/Spice).” February 2018. Accessed August 7, 2019.

    Tai, Sherrica; Fantegrossi, William E. “Synthetic Cannabinoids: Pharmacology, Behavioral Effects, and Abuse Potential.” Current Addiction Reports, June 2014. Accessed August 7, 2019.

    Raichlen, David A.; Foster,  Adam D.; Gerdeman, Gregory L.; Seillier, Alexandre; Giuffrida, Andrea. “Wired to run: exercise-induced endocannabinoid signaling in humans and cursorial mammals with implications for the ʻrunnerʼs high.ʼ” The Journal of Experimental Biology, December 2011. Accessed August 7,2019.

    Sallaberry, Chad A.; Astern, Laurie. “The Endocannabinoid System, Our Universal Regulator.” Journal of Young Investigators, June 2018. Accessed August 7, 2019.

    Tai, Sherrica; Fantegrossi, William E. “Pharmacological and Toxicological Effects of Synthetic Cannabinoids and Their Metabolites.” Current Topics in Behavioral Neurosciences, July 2017. Accessed August 7, 2019.

    Abouchedid, Rachelle; Ho, James H.; Hudson, Simon;  Dines, Alison; Archer, John R.H.; Wood, David M.; Dargan, Paul I. “Acute Toxicity Associated with Use of 5F-Derivations of Synthetic Cannabinoid Receptor Agonists with Analytical Confirmation.” The Journal of Medical Toxicology, July 2016. Accessed August 7, 2019.

    Kassai, Szilvia; Pintér, Judit Nóra; Rácz, József; Böröndi, Brigitta; Tóth-Karikó, Tamás; Kerekes, Kitti; Gyarmathy, V. Anna. “Assessing the experience of using synthetic cannabinoids by means of interpretative phenomenological analysis.” Harm Reduction Journal, February 2017. Accessed August 7, 2019.

    Miliano, Cristina; Serpelloni, Giovanni; Rimondo, Claudia; Mereu, Maddalena; Marti, Matteo; De Luca, Maria Antonietta. “Neuropharmacology of New Psychoactive Substances (NPS): Focus on the Rewarding and Reinforcing Properties of Cannabimimetics and Amphetamine-Like Stimulants.” Frontiers in Neuroscience, April 2016. Accessed August 7, 2019.

    Cooper, Ziva D. “Adverse Effects of Synthetic Cannabinoids: Management of Acute Toxicity and Withdrawal.” Current Psychiatry Reports, June 2016. Accessed August 7, 2019.

    Sherpa, Dolkar; Paudel, Bishow M.; Subedi, Bishnu H.; Chow, Robert Dobbin. “Synthetic cannabinoids: the multi-organ failure and metabolic derangements associated with getting high.” Journal of Community Hospital Internal Medicine Perspectives, September 2015. Accessed August 7, 2019.

    Fox, Maggie. “’People were just bleeding’: Doctors describe tainted pot emergency.” NBC Health News, September 27, 2018. Accessed August 7, 2019.

    Feinstein, Douglas L.; Akpa, Belinda S.; Ayee, Manuela A.; Boullerne, Anne; et al. “The emerging threat of superwarfarins: history, detection, mechanisms, and countermeasures.” Annals of the New York Academy of Sciences, June 2016. Accessed August 7, 2019.

    Castaneto, Marisol S.; Gorelick, David A.; Desrosiers, Nathalie A.; Hartman, Rebecca L.; Pirard, Sandrine; Huestis, Marilyn A. “Synthetic Cannabinoids: Epidemiology, Pharmacodynamics, and Clinical Implications.” Drug and Alcohol Dependence, November 2014. Accessed August 7, 2019.

    Sherman, Brian J.; McRae-Clark, Aimee L.; Baker, Nathaniel L.; Sonne, Susan C.; Killeen, Therese K.; Cloud, Kasie; Gray, Kevin M. “Gender differences among treatment-seeking adults with cannabis use disorder: Clinical profiles of women and men enrolled in the Achieving Cannabis Cessation – Evaluating N-acetylcysteine Treatment (ACCENT) study.” The American Journal on Addictions, March 2018. Accessed August 7, 2019.

    Johnston, Loyd D.; Miech, Richard A.; O’Malley, Patrick M.; Bachman, Jerald G.; Schulenberg, John E.; Patrick, Megan E. “Monitoring the Future National Survey Results on Drug Use 1975-2018: Overview, Key Findings on Adolescent Drug Use.” University of Michigan, January 2019. Accessed August 7, 2019.

    Riederer, A.M., Campleman, S.L., Carlson, R.G., et al. “Acute Poisonings from Synthetic Cannabinoids — 50 U.S. Toxicology Investigators Consortium Registry Sites, 2010–2015.” CDC Morbidity and Mortality Weekly Report, July 2016. Accessed August 7, 2019.

    The Center for Forensic Science Research and Education. “Trend Report: Q4 2018 Synthetic Cannabinoids in the United States.” (n.d.). Accessed August 7, 2019.

    The Center for Forensic Science Research and Education. “Trend Report: Q1 2019 Synthetic Cannabinoids in the United States.” (n.d.). Accessed August 7, 2019.