Public advisory

Limitations of test strips to check illegal drugs for dangerous substances

Last updated


Test kits designed to detect illegal drugs
Health products - Product safety
What to do

Treat all illegal drugs as though they are potentially contaminated with unknown dangerous substances.

Affected products

Illegal drugs


With the growing availability of test strips on store shelves and online, Health Canada is reminding Canadians of the potential limitations of test strips to detect xylazine, fentanyl and other dangerous substances in illegal drugs.

There are some test strips on the market designed to detect xylazine, fentanyl and some of its analogs (i.e. similar chemicals, such as carfentanil) in an individual's urine sample to determine whether they have taken the drug. Health Canada evaluates these to confirm their safety, quality and effectiveness and has authorized them for this specific use only.

Others are used to detect xylazine, fentanyl and some of its analogs in substances that are, for example, seized by law enforcement. Testing strips for xylazine or fentanyl may also be sold directly to consumers. They are sold as consumer products and Health Canada does not review them for evidence of effectiveness as we do for medical devices.

No test is 100 per cent effective at detecting all potentially dangerous substances in illegal drugs. A false negative could result in a fatal overdose. Treat all illegal drugs as though they are potentially contaminated with unknown and dangerous substances.

What you should do

Use every precaution, even if you or your friends use fentanyl or xylazine test strips:

  • Never consume alone.
  • Consider consuming a smaller dose: start low and go slow.
  • Don't mix opioids with alcohol or other drugs.
  • Go to a supervised consumption site if your community has one.
  • Carrynaloxone, which can temporarily reverse an opioid overdose. Make sure that you, and the people with you, know how to administer it.
  • Call 9-1-1 or your local emergency help line if you think someone is having a drug overdose.
  • Get your opioid overdose wallet card and carry it with you. Know what to do.

Limitations of test strips for illegal drugs

Test strips, whether they are a medical device or not, can provide false negatives. A false negative result means that the test strip did not detect a targeted drug even though the drug was present in the sample. This could lead to a false sense of security, resulting in overdose or death.

There are many reasons test strips may not detect all drugs present:

  • The test strips may only be able to detect certain substances, such as xylazine or fentanyl, and not other toxic substances that might be present, like carfentanil.
  • Illegal drugs can be mixed unevenly with other substances, so the portion tested may not contain the same amount of the drug as that which is to be consumed.
  • Other substances mixed in the sample could interfere with the accuracy of the test.
  • The sample size tested may be too limited to detect a specific substance.

Health Canada is working with companies of authorized products to include warnings on the packages of test strips that detect the presence of xylazine, fentanyl and/orits analogs to better inform consumers about the risks of unreliable results when using the test strips to check the illegal drugs they plan to consume.

For more information:

Additional information

Original published date:
Alert / recall type
Public advisory
Health products - Drugs
Published by
Health Canada
General public
Identification number
Media and public enquiries

Media Enquiries

Health Canada


Public Enquiries


1-866 225-0709

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