Medical Cannabis and Drug Testing in New Zealand

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For medical cannabis patients, concerns about prescriptions showing up in workplace or law enforcement drug tests and potentially affecting their employment or driving abilities are common. This article aims to clarify these concerns and provide helpful information.

What Substances Do Drug Tests Target?

In New Zealand, drug tests typically screen for six substances. One of these is THC-COOH, a byproduct created when the liver processes THC. It is targeted in drug tests because it remains in the body longer than THC. The five other substances include amphetamine, methamphetamine, cocaine metabolite, opiates and benzodiazepines. Check out Labtests drug testing FAQ.

Will Medical Cannabis Show Up in a Drug Test?

There is no differentiation between recreational or medicinal cannabis use, which means that medical cannabis containing THC will show up in drug tests. Regular consumption of THC-based treatments can cause a buildup of THC in the body, which is likely to be detected in drug screens.

CBD and Drug Testing

CBD generally does not result in a positive cannabis drug test, as tests typically screen for THC, not CBD. However, full-spectrum CBD may contain enough THC to register in a drug test.


How Long Can Cannabis be Detected in the Body?

A detailed analysis of the length of time cannabis stays in the body requires an understanding of the various factors that influence the detection of THC. Factors such as frequency of use, dosage, individual metabolism, and the testing method used all play a role in determining how long cannabis remains detectable in the body.

  1. Frequency of Use: The frequency of cannabis use has a significant impact on the length of time it stays in the body. Occasional users may have cannabis clear from their system in a few days, while regular users may experience a detectable presence for several weeks or even months after their last use.
  2. Dosage: The amount of cannabis consumed can also affect how long it stays in the body. Higher doses of THC will take longer to be eliminated from the body than lower doses.

  3. Individual Metabolism: Every person’s body processes cannabinoids differently. Factors such as age, gender, body fat, and genetics can influence how quickly the body metabolises THC. Faster metabolism rates will result in a quicker elimination of cannabis from the body, while slower metabolism rates will cause it to remain detectable for longer periods.

  4. Drug Testing Methods: Different drug testing methods also have varying detection windows for cannabis. Here is a breakdown of the typical detection times for each testing method:

    • Urine Testing: This is the most common method for drug testing. Occasional users may test positive for THC in urine for up to 3-5 days, while regular users may test positive for up to 30 days or more after their last use.
    • Saliva Testing: Saliva tests can detect THC in occasional users for approximately 24-72 hours after use, and in regular users, it can remain detectable for up to a week or more.
    • Hair Follicle Testing: Hair tests can detect THC for up to 90 days after use. However, this method is less common due to its higher cost and longer detection window, which may not be relevant for many testing purposes.
    • Blood Testing: Blood tests can detect THC in occasional users for approximately 3-4 hours up to 1-2 days, and in regular users, it can remain detectable for up to a week or more. Blood tests are less common, primarily used in accident investigations or DUI cases.

Consequently, the length of time cannabis stays in the body depends on various factors, making it challenging to provide a precise detection window for every individual. Understanding these factors and the detection windows for different testing methods can help medical cannabis patients and users make informed decisions about their consumption and potential drug test outcomes.

Situations for Drug Testing

There are various situations in New Zealand where drug testing may be required. These include pre-employment screening, random roadside testing, post-incident testing, competitive sports testing, reasonable cause testing, rehabilitation, pre-employment/pre-contract, and internal transfer.

For example, pre-employment drug testing may be required for certain industries to ensure that employees are not under the influence of drugs or alcohol while on the job. Random roadside drug testing is also becoming more common as part of the Ministry of Transport’s Road to Zero campaign, which targets safe driving practices. Post-incident testing may be conducted after an accident or near-miss to determine if drug use was a contributing factor. Drug testing may also be required in competitive sports to ensure that athletes are not using performance-enhancing drugs.

Employers may also conduct drug tests if they have reasonable cause to suspect that an employee is under the influence of drugs or alcohol while at work. Similarly, if an employee is undergoing rehabilitation for drug or alcohol addiction, they may be required to undergo drug testing as part of their treatment plan. Finally, drug testing may be required when an employee is transferring to a new role within the same organisation to ensure that they meet the drug and alcohol policy requirements for their new position.

Consequences of Failing a Drug Test

Consequences for failing a drug test can vary significantly depending on the specific situation. For instance, if the test is required as part of a pre-employment screening process, a positive result may result in the job offer being revoked or the candidate being disqualified from consideration for the position. If the test is required due to a workplace incident or safety concern, the consequences may include suspension or termination of employment.

In some cases, a positive drug test may not result in any immediate consequences, but the results will be reported to the appropriate parties as required by law or organisational policy. For instance, if a drug test is required as part of a criminal investigation, a positive result could lead to legal consequences or further investigation.

In certain situations, a medical defence may be available for individuals who test positive for drugs due to prescribed medication or medical treatment. This may apply to individuals who use medical cannabis as part of their treatment plan. However, it is important to note that the specific circumstances of each case will be considered when determining whether a medical defence is applicable, and it is not a guarantee that negative consequences will be avoided.

Consult with your GP or a specialist doctor at a Cannabis Clinic to provide evidence of your legal medical cannabis use. They can help you obtain documentation for your employer or other authorities to prove that your cannabis use is medically justified.

Support for Medical Cannabis Patients

The Cannabis Clinic offers a Medicinal Cannabis Card to help patients provide identification and proof of their medical cannabis use. Although not a legal document, it may be helpful in various situations. Cannabis Clinic doctors also offer expert advice and support to help patients navigate the challenges and stigma associated with medical cannabis use.


Understanding the complexities of drug testing and medical cannabis in New Zealand is essential for patients relying on these treatments. If you’re considering medical cannabis as a treatment option, consult with an experienced doctor to guide you through the process and address any concerns.


Medical Cannabis and Drug Testing in New Zealand

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Disclaimer – medicinal cannabis and CBD oil are unapproved medicines in NZ which means that there is no conclusive evidence for their effect, apart from Sativex. Many doctors do not routinely prescribe cannabis medicines. The above article was written for general educational purposes and does not intend to suggest that medicinal cannabis can be used to treat any health condition. Please consult with your healthcare provider. 

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