How Long Does K2 Stay In Your System?

Experts don’t know how long the synthetic cannabinoids in K2 stay in your system. But some can be detected within 72 hours of use. More on the metabolism of K2 ingredients here.

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Reviewed by: Dr. Dili Gonzalez, M.D.

ARTICLE OVERVIEW: We really do not know a lot about how K2 works and stays in the body. But we do know that the length of time that K2 stays in your system depends on which synthetic cannabinoids are in the mixture. More on metabolism of synthetics here…with a section for your questions at the end.


What’s In K2?

K2 is a brand of mixture of herbs and spices that is sprayed with chemicals called synthetic cannabinoids. These synthetics are chemically similar to THC, the psychoactive ingredients in marijuana. The five primary chemicals used in K2 are:

  • Cannabicyclohexanol
  • CP-47,497
  • JWH-018
  • JWH-073
  • JWH-200

However, it’s not easy to determine exactly what is in K2. There are currently over 140 synthetic cannabinoids on the market. Keep in mind that K2 is an unregulated mixture of any of these different compounds. Therefore, it is a very dangerous drug.

What Does K2 Do To The Body?

K2 has only been around a few years, what is known is that the chemicals found in it attach to the same nerve cell receptors as THC, the main mind-altering ingredient in marijuana.

So far, there have been few scientific studies of the effects of synthetic cannabinoids on the human brain, but researchers do know that some of them bind more strongly than marijuana to the cell receptors affected by THC, and can produce much stronger effects. The resulting health effects can be unpredictable and dangerous.

The long-term effects of using synthetic cannabinoids are unknown. The entire scope of chronic use has not been studied. As use increases in frequency and duration, there are greater risks of ill effects of synthetic marijuana abuse including:

  • Death.
  • Heart attacks.
  • Injuries due to erratic or violent behaviors.
  • Kidney damage.
  • Onset or exacerbation of mental health disorders.
  • Respiratory issues similar to those seen in tobacco smokers.
  • Seizures.

The mental health consequences can be even more severe. There are reports of extreme depression with suicidal thoughts that can endanger the safety of the person abusing synthetic cannabinoids. Some people who suddenly stop using synthetic cannabinoids after frequent use have reported severe symptoms such as:

  • Chest pain.
  • Difficulty breathing.
  • Palpitations.
  • Rapid heart rate.
  • Seizures.

The severity of these withdrawal-like symptoms may be related to how much and how long someone has used synthetic cannabinoids. Further, we still do not know all the ways K2 may affect a person’s health or how toxic it may be. However, it is possible that there may be harmful heavy metal residues in K2 mixtures that can cause even more serious long-term effects.

Peak Levels of K2

The chemical structure of synthetic cannabinoids differs from that of THC. As a result, the way that synthetics metabolize in the body are also different. Like marijuana, howver, peak levels of synthetic cannabinoids are achieved relatively quickly. K2’s peak levels occur within 10-45 minutes after smoking, or longer after eaten or brewed in tea.

When inhaled, K2 products are rapidly absorbed into the bloodstream. Smoking K2 produces peak concentrations within minutes after intake with blood/serum concentrations of 10 mg/L. These peak levels then rapidly decline and are only detectable for hours to days. For example, the synthetic cannabinoid JWH-018 is detectable for up to 48 hours.

Oral intake produces much lower serum concentrations, but detectability might be extended upon oral ingestion. In some cases, K2 was detected up to 5 days after oral intake.


K2’s duration of effect varies by type of cannabinoid found in a K2 mixture. Likewise, the half-life of K2 ingredients varies by:

  • Dosage
  • Frequency of use
  • The user
  • Type of cannabinoids

However, both half-life and duration of effect of synthetic cannabinoids tend to be longer than THC. In general, the half life of compounds found in K2 is longer than THC (3-5 days), which is what causes increased duration of effects in users.

K2 Detection Window

Recent studies demonstrate that is possible to detect some of the more popular synthetic cannabinoids on yoururine, blood, saliva or hair. In fact, specific cannabinoid drug screens look for the presence of synthetic cannabinoids or one of its metabolites, which are chemicals that your body makes to process the drug.

The main detection windows for K2 are:

Blood: Synthetic cannabinoids can be detected in chronic users’ serum 30 days after last use. So, detection of K2 or its metabolites in blood might not necessarily mean recent intake.

Hair:Like other illicit drugs, K2 can be detected in a hair sample for 90 days or more after last use. This is why hair drug screens usually serves to monitor long-term consumption patterns or prove abstinence.

Saliva: Oral concentrations of peak levels of synthetic cannabinoids are low and range between 3 -35 mg/L after smoking, rapidly declining until becoming undetectable after several hours. This might render saliva a good matrix to document recent use or to monitor frequent users.

Urine:After a single smoked dose, the detection window is 2–3 days in urine. The detection window after oral consumption is 10 days in urine.

As K2 potentially contains hundreds of compounds, some still unknown, the emergence of synthetic cannabinoids will pose continuous challenges to clinical and forensic laboratories. With each new compound, the forensic community must address three major issues:

  1. Identification of suitable biomarkers via in vitro studies to detect intake.
  2. The need for reference standard synthesis.
  3. Continuous updating and validation of analytical methods, which is a time-consuming, cost- and labor-intensive process.

K2 Drug Testing

Synthetic cannabinoids do not produce positive results in routine cannabis drug tests; they are detectable in the urine only if they are specifically searched for. Again, the detection time for K2 in urine is about 2-3 days after consumption.

So, what does urine based K2 drug testing involve?

K2 urine testsare made with strips. This strip is immersed directly into the urine sample, which prevents any liquid handling. The test is a qualitative assay test which delivers a type “NO or YES” result, which translates to a “NEGATIVE” or “POSITIVE” result.

False Positives

A K2 test will be positive if the test sample contains at least 25 nanograms of traces of synthetic cannabinoids per milliliter of urine. Conversely, it will be negative if the sample contains less or not at all. However, there are some cases when a false positive can occur.

For example, the urine test for K2 has been determined to cross react with the drug Lamictal (lamotrigine). Specimen from individuals taking this prescription drug will likely register a false positive for K2. All presumptive positive screens should be sent to a confirmation lab for analysis.

What If I Test Positive?

Testing positive for K2 can result in the loss of a job, getting kicked out of school, or even jail time if it’s tied to probation requirements. So, what can you do if a K2 test comes out positive? Well, here are our suggestions:

Failed a WORKPLACE drug test?

You have the right to oppose to drug test results if you believe the test results are in error. To prove your innocence:

  • You can ask for a hair sample drug test.
  • You can require the laboratory to test your sample again.
  • Your employer might allow you to retake the test.
  • Your employer can require an additional test with only one hour notice.

Failed a CLINICAL drug test?

If you feel that your test result is incorrect and that you haven’t taken K2 but are showing a false positive result, you can:

  • Ask for a laboratory confirmatory test.
  • Participate in drug screening and assessment performed by your doctor or another medical professional.
  • Talk with your practitioner about lamotrigine.

Failed a STUDENT drug test?

Firstly, the student drug testing in schools is not to punish students. Schools drug test to prevent addiction before it happens. So, if you’ve started to use drugs, the school really wants to help you become drug-free.

If you fail a K2 drug screen, your parents or legal guardians will be informed, but the school may allow you to retake the test or can require the laboratory to retest your sample or collect a new sample in a short window of time.

Home Tests

You can use the home urine tests to detect K2, however this type of drug kit is not recommended. Home drug testing kits are imprecise and can yield false positives. For best results, seek a consultation with a private, specialized laboratory.

K2 and Addiction

Believe it or not, K2 is addictive. Case reports describe psychotic episodes, withdrawal, and dependence associated with use of synthetic cannabinoids found in K2. So, most experts think that K2 has an addiction similar to syndromes observed in marijuana abuse.

K2 addiction is treatable.

If you think that you have problems with K2, please ask for help!

Remember that the sooner you seek help to quit, the greater the chances for long-term recovery success. You can learn more about K2 addiction, available treatment programs, what the rehab process entails, and how to change your life for the better starting TODAY in this K2 and Spice Addiction Treatment Programs and Help guide.

Problems with K2?

K2 smokers are exposed to synthetic cannabinoids that are extremely variable in composition and potency, and are at risk of serious, if not lethal, outcomes. Not knowing what’s in K2 makes potential overdose more likely and increases chances of both short and long term adverse effects.

Got questions?

If you have questions about K2 or want to discuss its effects, please let us know. We will be happy to respond to your questions personally and promptly and help you as best as we can.

NIDA: Synthetic cannabinoids (K2/Spice)
NIH: Synthetic cannabinoids pharmacokinetics and detection methods in biological matrices
DEA Drug Fact Sheet on K2
Drug Free NJ [dot] org information on K2
Utah State legislature information on K2
About the author
Lee Weber is a published author, medical writer, and woman in long-term recovery from addiction. Her latest book, The Definitive Guide to Addiction Interventions is set to reach university bookstores in early 2019.
Medical Reviewers
Dr. Dili Gonzalez, M.D. is a general surgeon practicing women's focused medici...

All of the information on this page has been reviewed and verified by a licensed medical professional.

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