From December 2025, random roadside drug testing for THC and other substances will begin in Wellington and roll out nationwide in 2026. This applies to all drivers, including those prescribed medicinal cannabis.
If you are a medicinal cannabis patient, you could still test positive for THC – however, a medical defence may apply if you are following your doctor’s instructions. This page explains what to expect and how we can support you through the process.
Watch Our Video GuideIf pulled over, you may be asked to take a saliva swab test:
If a roadside test is confirmed by laboratory testing and exceeds the legal threshold, you can apply for a medical defence through the Police. Your application must clearly show that the detected substance was lawfully prescribed and used as directed.
To apply, you must provide;
Applications can be submitted online or by sending the completed Medical Defence form to the Police Infringement Bureau by email or post.
Submit Online Application Learn MoreOur CEO Dr Waseem explains what’s changing and how we’re here to help. Watch our three-part video series:
Understand how saliva testing works and the penalties involved
Saliva tests, impairment and what your prescription does (and doesn’t) cover
How to dispute a fine with our support and what documentation we can provide
We’ll keep this page updated with any changes to the law, best practice guidance, and helpful tools to stay compliant and safe.
Yes, you can drive as long as you are not impaired. Everyone’s different, but generally, we recommend waiting at least 6 hours after inhaling a THC-containing product and at least 10 hours after consuming THC orally before driving.
The tricky part is if you are stopped for a roadside test. If THC shows up in a saliva test, you will still need to stop driving for 12 hours, even with a valid prescription. The medical defence comes later. It is used after an infringement is issued, not during the roadside process.
It varies from person to person. If you use THC often, it can show up in saliva tests for up to 72 hours. If you use it less often, it is usually closer to 4-12 hours. Even when you feel clear and not impaired, small amounts can still be present and trigger a positive saliva test.
You will need to immediately stop driving for 12 hours. Police will send your saliva sample to a lab for confirmation. If the lab finds THC above the legal limit, you may receive a $200 fine and 50 demerit points.
After two positive saliva tests, police must tell you to stop driving for 12 hours. They do not usually tow your car or drive you home. They expect you to arrange a safe way to leave, like calling someone to pick you up or booking an uber or taxi.
Your car will normally be left parked safely at the roadside. Police only move or impound a vehicle if it is unsafe where it is. You will not be left in the middle of the road, but you do need a safe ride because driving again during that 12 hour period is a separate offence.
Yes, you can. CBD on its own is not impairing, and it is not one of the substances police are looking for in the roadside saliva test. Pure CBD products will not trigger a saliva test for THC.
The only time to be a little cautious is if you use a full spectrum CBD product, because these contain tiny trace amounts of THC. Those traces are usually low, but for some people they may still register on a saliva test for a short period after use.
If you’re prescribed CBD and using it as directed, you’re safe to drive as long as you feel alert and unimpaired. If you ever want to double check the type of CBD you’re taking or how to use it safely around driving, our clinical team is always here to help.
Yes, you can drive while taking THC, provided you follow your doctor’s timing guidance and feel fully normal and unimpaired before driving. However, the new roadside saliva test does not measure impairment or how you feel or how safely you are driving. It simply detects the presence of THC in your system, and if it shows up twice, you must stop driving for 12 hours, even if you used your medication responsibly and feel completely normal.
For most patients, the safest approach is timing. Many people use THC at night and leave plenty of time before they need to drive the next day. Your doctor’s guidance is important here, and sticking to the recommended waiting periods gives you the best protection.
If you ever face an infringement, your medical defence comes into play afterward, not at the roadside. As long as you are prescribed THC and follow your doctor’s instructions, we can support you with the documentation you need.
Not at the time of the test. Police cannot accept medical defences at the roadside. However, if you receive an infringement notice, you can challenge it with proof of prescription and clinical support.
We can provide you with:
It’s a legal challenge you can make after being penalised, showing you were following a legal prescription as advised by your doctor. You must provide supporting evidence.
Pure CBD isolate does not contain THC and should not result in a positive test. However, full-spectrum CBD products contain trace THC levels that may still cause detection, depending on sensitivity.
Timing is the biggest factor. Leave enough time between using THC and driving. Good oral hygiene helps too. Rinse your mouth, brush your teeth, and avoid using THC close to when you plan to be on the road. Make sure to talk to your Cannabis Clinic doctor for personalised advice.
No. You can test positive for THC even if you are not impaired. Saliva tests detect the presence of substances, not real-time impairment.
The legal threshold doesn’t measure how impaired you are. It is not like the alcohol system. There is no scale that shows whether you are safe to drive.
The Securetec DrugWipe® 3 S code S304G.91 is the roadside saliva testing device used by police to detect recent drug use. It collects a small saliva sample on a test pad and gives a rapid result. It is designed to identify selected drugs, including THC, through an immunoassay that reacts to specific substances present in oral fluid.
The Securetec DrugWipe® 3 S code S304G.91 detects oral THC at a positive screening threshold of 15 ng / mL. A result above this level triggers a second saliva test at the roadside. If both tests are positive, you must stop driving for 12 hours. Laboratory confirmation is required after the roadside process.
Carrying your prescription does not change the roadside process. Medical defences are only submitted online after an infringement notice is issued. Police do not apply medical defences at the roadside. Two positive saliva tests mean an automatic 12 hour driving ban, whether you hold a prescription or not. Carrying your prescription will not prevent the 12 hour stand-down.
The CannaCard is not a legal document, so it will not change the roadside testing process or prevent a 12 hour stand down if you return two positive saliva tests. Medical defences are only submitted online after an infringement notice is issued.
That said, many patients like carrying their CannaCard because it helps them stay calm and gives a sense of peace of mind. It is a simple way to show you are a legitimate patient, even though it does not hold legal status.
The Roadside drug tests do not detect alcohol. Police use a separate breath testing device for alcohol. Police have authority to run both tests during the same stop, and they will likely often use them together.
Yes, if you are using a legally prescribed medicinal cannabis product that contains THC, then you may test positive on a roadside saliva test.
THC can stay in your saliva for 4 to 12 hours, sometimes longer, and saliva testing detects presence, not impairment. Even with a legal medicinal cannabis prescription, you may still face penalties if your result is above the legal limit. You must not drive if you feel impaired at any time, regardless of when you last took your medication.
If you are stopped at the roadside, you may be asked to complete a saliva swab test. If the first test is positive, a second saliva test will be done straight away. If both tests are positive, you will be immediately required to stop driving for 12 hours while a laboratory confirmation is carried out.
If the lab results shows levels above the legal threshold, penalties can include a $200 infringement notice and 50 demerit points. If you refuse the saliva test or appear impaired, police may request a blood test instead..
If you receive an infringement and you are prescribed medicinal cannabis and follow your doctor’s instructions, you can present a medical defence to avoid a fine and demerit points.
A medical defence does not apply during the roadside process; a positive saliva test requires you to stop driving immediately for 12 hours. A medical defence can be used later through the online process to dispute an infringement.
We can help you with this:
Being a medical patient still matters. The roadside process is the same for everyone, but what happens afterward is very different. If you follow your doctor’s instructions, you have access to a medical defence that non-patients do not have. This defence is submitted after an infringement is issued, and it gives you a pathway to avoid fines and demerit points.
Remember, if you test positive twice and do not have a valid medical defence, you risk losing your driver licence.
We hear your frustration. The roadside rules feel unfair, and many patients are reacting the same way. The important part is that being a medical patient does protect you, just not at the exact moment you are tested.
The saliva test process is the same for everyone, but the outcome afterward is not. Once an infringement is issued, only prescribed patients have the ability to use a medical defence to avoid fines and demerit points. That protection does not exist if you go back to the black market.
Staying with the clinic means you get legal cover, clinical support, and clear documentation that proves your use is legitimate. It also keeps your treatment safer, consistent, and properly guided by a doctor. Going back to an illegal source removes all of that and puts you at greater legal and safety risk.
If you ever need help with medical defence letters, prescription proof, or support after a test, we are here to back you.
We understand why you feel worried. The law is based on detection, not actual impairment, and that creates a real problem for people who use their medication responsibly (and as prescribed) at night and need to drive the next day.
Many patients are in your situation. You need your treatment, and you also need to keep your licence to work. The current testing system does not reflect the way medicinal cannabis is prescribed or used, and it can put patients in an unfair position.
The best support we can give is helping you manage the timing of your medication, keeping your prescription up to date, and making sure you have the right documentation if you ever need a medical defence. If you use THC only at night and follow your doctor’s guidance, you are doing everything right, even if the law feels out of step with real life.
You do not need to face this alone. We are here to help you find the safest approach for your work, your treatment, and your legal protection.
Patients are doing everything right, using their medication responsibly, and still facing a system that doesn’t reflect real impairment. Your frustration is valid.
We’re not sitting on the sidelines. We made a formal submission to the Transport and Infrastructure Select Committee before this law was passed, and we continue to raise concerns with police and politicians so they understand how this law affects real patients who rely on prescribed treatment.
On the patient side, our focus is making sure you’re protected as strongly as possible under the current framework. That includes medical defence support, prescription documentation, clinical letters, and step by step help if you ever face an infringement. We stay in touch with policymakers so your experiences are heard, and we push for clearer guidance and fairer rules.
This situation is not ideal, and we share your concerns. While the law stands as it is, we’re here to support you with practical tools and strong advocacy, and we’ll keep pushing for better, safer, and more sensible policy for medical users.
If you want to explore the new roadside drug testing rules in more detail or access tools that can help you stay informed, these resources are a good place to start:
If you’d like to understand your own risk before driving, you can order an at-home saliva test to check for the presence of THC
Whilst not a legal document, carry proof of your legal prescription with a CannaCard for added peace of mind.
If you require formal letters, documentation, or guidance on a medical defence, our team can support you.
Our team can give tailored advice to minimise risk and keep you within the law.
Speak to One of Our TeamNavigating drug testing as a patient can be stressful. We’re here to make sure you don’t do it alone. Reach out anytime, we’ve got your back.
Ngā mihi,
The Cannabis Clinic Team
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