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62 Harris St, Harris Park NSW 2150

PO Box 9017 Harris Park NSW 2150

02 8001 2535 | info@dasa.net.au

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Can food or drink produce a non-negative drug test?

Onsite tests are screening devices so they will detect any substances that are chemically like the target drugs. For this reason, results from onsite devices are always called non-negative, rather than positive.  A confirmation sample is then analysed by a laboratory to determine exactly what is in it. The laboratory analysis is specific and accurate. Some foods and drinks, such as hemp seeds, poppy seeds, kombucha and protein bars may trigger a non-negative result in the onsite device. That's why we ask workers undergoing a drug and alcohol test to not eat or drink anything for at least 10 to 15 minutes prior.


Hemp seeds are a popular addition to many people’s diets as they contain protein, vitamins and fatty acids. Hemp is derived from the cannabis plant, but hemp seeds purchased in Australia contain no or very low levels of THC (the psychoactive component of marijuana) and so a non-negative result is unlikely. However, hemp seeds purchased from overseas may contain higher levels of THC and so the risk of a non-negative result is increased. Generally, a lot of hemp seeds will need to be eaten to return a non-negative result. However, regardless of the source of THC a result above the target cutoffs of the onsite device suggests impairment. 


Poppy seeds can produce a non-negative result for opioids, specifically morphine and codeine. However, an analysis of the confirmation sample by the laboratory will show that the concentrations are very low. Opioids taken as medications or as a drug of abuse will normally have a concentration 40 times higher than what will be seen with a slice or two of poppy seed cake or bread.


Kombucha is a fermented drink made from brewed tea and contains a very low level of alcohol (so low that it is not considered an alcoholic drink). A positive alcohol test is possible, especially for workplaces with a BrAC of 0.0%. By waiting 10-20 minutes before retesting for confirmation will allow this low-level alcohol to be metabolised.


Some high protein bars may return a non-negative result for amphetamine or methamphetamine. This is probably due to the breakdown of the amino acids into substances that are similar to the chemical structure of amphetamine stimulants. Once again, the laboratory analysis should be able to determine if drugs of abuse have been taken.


Our Scientific Director, John De Mellow, is happy to answer any questions you may have regarding onsite drug testing. Contact us on 02 8001 2535.