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Everything You Need to Know About Instant Drug Tests

Published on: August 25, 2017

Written by: Confirm BioSciences.

Instant Drug Test Kits: How Do They Work?

Hardly anybody truly bothers to understand how a drug test is done, except perhaps those who are trying to pass one. The common preconception involving how drug test is performed usually involves submitting blood, urine, saliva or hair samples to a drug testing laboratory and then waiting a few days for the results.

More recently, instant drug tests have started to become widely used throughout the world. These tend to look like cups, dipsticks, test tubes or oversized cotton buds. If they’re cheaper than lab tests, does it mean they’re less reliable? Let’s start out with a few basic questions.

What are Drug Metabolites?

Anything and everything that we digest will become chemically altered or metabolized. For drugs in particular, the process of metabolism results in substances (metabolites) that are either similar or different to the original drug as far as toxicity or therapeutic activity is concerned. Drug metabolism primarily happens in the liver. It is where inactive drugs are metabolized or converted into their active form (and vice versa). In a drug test, samples are analyzed for the presence of a parent drug and/or its metabolites.

Learn More About Drug Metabolites

How are Drugs Eliminated From the Body?

Eventually, the drug and/or its metabolites are eliminated mostly via urine (kidneys) and in the bile (from the liver). Other forms of elimination (in smaller amounts) happen through saliva, breast milk, sweat or even in exhaled air (especially for inhaled anesthetic drugs). Some drug metabolites traveling around in the bloodstream get deposited into the hair follicles and are eliminated from the body as the hair shaft grows out of the scalp.

When you take drugs, how soon do they show up in a drug test?

Marijuana Molecular Formula

This section explains when drugs become detectable through a variety of drug test methods while using different sample types. We will use marijuana (cannabis) consumption as an example.


The most psychoactive cannabis molecule in its raw or purest state is delta 9-tetrahydrocannabinol (Δ9-THC). It is Δ9-THC that is present in the body shortly after smoking marijuana. This is true for most other drugs – it is the parent drug that is found in saliva, not its metabolites. For this reason, saliva tests that identify Δ9-THC at a cut-off level of 25ng/ml within minutes up to 6-24 hours from smoking pot tend to be the most effective tests.


Upon inhalation, Δ9-THC is absorbed thru the lungs and is detectable in plasma within seconds, reaching peak concentrations within 3-10 minutes. Inside the body, the Δ9-THC molecule is metabolized into a secondary active metabolite called 11-Hydroxy-Δ9-tetrahydrocannabinol (11-OH-THC). Further metabolism converts 11-OH-THC into the inactive form 11-nor-9-carboxy-Δ9-tetrahydrocannnabinol (THCCOOH). 11-OH-THC and THCCOOH reach peak levels in the blood within 15 minutes and 81 minutes respectively.


Urine Cup Leakage

The secondary active metabolite 11-OH-THC is later excreted mostly thru the bile. The inactive metabolite THCCOOH on the other hand gets eliminated from the body primarily in the urine. After smoking around 27mg of Δ9-THC, peak urine concentrations of 11-OH-THC and THCCOOH were observed within 3 hours and 4 hours respectively.


A 2015 study at the Institute of Forensic Medicine in Freiburg, Germany showed that after giving participants a daily dose of THC or THCA (non-psychoactive), the amount of THC metabolites in their hair after a 30-day period constituted what researchers consider to be scientifically irrelevant. Furthermore, older hair samples from the participants tested positive for THC.

They concluded that:

1) For THC metabolites to reach a significant level in hair via the bloodstream, users would have to consume extremely high amounts of THC.

2) Heavy users will consequently contaminate not only their own hair but (via external sources like second hand smoke) also through hand-to-hand contact, sebum and sweat.

While this study somehow debunks the current practice of testing hair for THC for occasional users, it further establishes hair testing as the most ideal method for establishing a history of heavy cannabis use. A 1.5 inch sample of hair cut close to the scalp will provide (approximately) a 90-day history.

Analytical Techniques for Detection and Analysis of Cannabinoids

Immunoassays – are chemical tests that detect the presence of and quantify specific analytes in samples of body fluid like blood or urine by using purified antigens and antibodies as reagents. Immune cells (B-lymphocytes) produce a protein (immunoglobulin) called an antibody when they are stimulated by an antigen, resulting in the formation of antigen-antibody complexes. It is these complexes that immunoassays detect and measure via an indicator reaction. Immunoassays can either be quantitative (measures the signal produced by the indicator reaction) or qualitative (negative or positive).

Some immunoassays can be as simple as mixing the sample with the reagents and making a physical measurement. They are called homogenous immunoassays. This is the principle behind many instant drug testing kits. Immunoassays provide a quick and efficient way to identify drugs and/or their metabolites, and are best suited as screening tests.

Many immunoassays make use of a “calibrator” or a solution that actually contains a specific analyte of interest. The signal strengths of the assay/ sample reaction and the assay/calibrator reaction are compared with each other.

Some of the more widely used immunoassays for detecting cannabinoids include:

Fluorescence Polarization

It is important to note that immunoassays are typically designed for specific drug classes, and substances that have similar chemical structures will likely “cross-react” and will result to a false positive. For this reason, non-immunoassay methods are usually recommended as confirmatory tests for immunoassay positives.

See Also: What is a False Positive Drug Test Result?

Chromatography – is a technique for the separation of a mixture, typically done in a lab environment. The mobile phase is a fluid in which the mixture is dissolved. It carries the mixture through a stationary phase where each component of the mixture gets separated from the others by virtue of the differences in the speed by which they travel. The mobile phase may be a liquid, gas or supercritical-fluid. An example of a stationary phase is a thin layer of silica.

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Some of the more widely used chromatography techniques for detecting cannabinoids include:

Thin Layer Chromatography (TLC)
High Performance Thin Layer Chromatography (HPTLC)
Gas Chromatography-Mass Spectrometry (GC-MS)
High Performance Liquid Chromatography-Mass Spectrometry (HPLC- MS)

While instant drug test kits are designed for drug screening purposes and use immunoassays, there are those that actually provide sample splitting so that in the event of a positive result, the rest of the same sample may simply be forwarded to the labs for confirmatory testing using various chromatography techniques.

In other words, these instant drug test kits are the product of years of technological research. In this instance, cheaper does not mean less reliable. Just remember to do your own research before buying one, and aim to buy the more trusted names within the industry.