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What is a False Negative on a Drug Test?

False Negative Drug Test Result

Most people are familiar with false positives on drug tests, but are unaware of false negatives. What is a false negative on a drug test, what can you do to prevent them and what should you do if you identify one?

What is a False Negative Drug Test?

A false negative is any time that under normal circumstances a drug test would be positive for an individual but for some reason results are negative. An example would be a patient that is prescribed Oxycodone that takes his medication consistently as prescribed, but has a negative drug test during his doctor visit.

In most cases this is caused by the patient either purposefully or accidentally altering their urine sample. The most common false negative drug test is due to water loading.

False Negatives From Water Loading & Adulteration

Water loading is the process where a person drinks an excessive amount of water prior to giving a sample. Urine that is clear with no yellow tint is usually indicative of water loading. You will need to perform separate adulterant tests for Creatinine, pH and protein levels to prove that a test has been diluted by a subject ingesting excessive amounts of water.


urine color drug test chart
This chart shows how shades of urine relate to dehydration. When analyzing drug test samples, some color is preferable because urine that is completely clear cannot be distinguished from water without further testing.


Without adulteration testing pure water will show negative on a drug test assay because the tests are only meant to detect the presence of a certain drug or metabolite in a substance, not to detect if the substance is a valid sample. Subjects can simply add water to their urine, but to fool a witness they will ingest an excessive amount of water to dilute the urine that comes from their own body.

There are several products available that claim to help users pass urine drug screens. These products range from nothing more than fortified tea that dilutes your urine to products that claim to seal in fat cells for several hours. Many of these products will speed up the timeframe which a person can pass a urine screen even if it’s for no more reason than they’ve diluted their urine.

Improper Drug Test Selection

A mistake made by organizations conducting drug tests is improper test selection. Every organization will have their own considerations when choosing a testing device, but some drug tests will not detect every illicit substance that people assume.

Semi-Synthetic Opiates

Many times a doctor prescribes their patient oxycodone or another semi-synthetic opiate, but uses a 5 panel drug test that only has a test for opiates. The doctor has seen positive tests for opiates from his patients that are prescribed oxycodone, but his new patient tests negative. One study found that oxycodone was detected in 12% of opiate immunoassay tests, and many other synthetic or semi-synthetic opiates also require a special test for accurate results. 


Most assays for benzodiazepines detect their presence in the urine by testing for nordiazepam and oxazepam, the main metabolites of most benzodiazepines. Agents that follow a different metabolic pathway, such as triazolam, alprazolam, clonazepam, and lorazepam, have poor cross-reactivity with the assay due to the absence of these metabolites and thus frequently produce false-negative results. Some doctors prescribe diazepam, oxazepam, and temazepam instead to reduce lab confirmations.

False Negatives From Very High Cutoff Levels

If your drug tests have high cutoff levels it is more likely for a user that has recently ingested drugs to produce a negative result.

The National Institute of Drug Abuse and the Substance Abuse and Mental Health Services Administration publish recommended cutoff levels for drug testing which most companies follow. Dozens of other federal agencies publish their own standard cutoffs (everyone from the Department of Transportation to the Nuclear Regulatory Commission) that are usually based off federal recommendations.

Even though the federal government publishes their own guidelines laboratories and manufacturers can create products that use whatever cutoff level they deem appropriate and the federal guidelines do change from time to time.

For example opiates and morphine have two widely used cutoff levels since the early 2000s because so many people were failing employment tests because the popularity of poppy seed muffins. The recommendation soared from 300ng/ml to 2000 ng/ml. The majority of tests will use this recommendation to stay compliant with as many federal regulations as possible, but the high sensitivity tests are still available.


Poppy Seed Muffin
Poppy seed muffins caused so many false positives in the 1990s that the NIDA introduced a new cutoff level for Opiates.


In practice there is no right answer. Some regions may have popular restaurants that sell poppy seed muffins, and some industries may have a high percentage of clients that anticipate testing and use gray-hat adulteration methods to get their levels under the cutoff.

Human Error

We advertise our drug tests as being 99% accurate, but in any situation that involves a human there is a possibility of introducing human error. A technician could mislabel tags, forget to confirm the temperauture on a sample or give a patient an opportunity to switch out a sample altogether.

Human error is even more likely in a laboratory where a technician has to prepare an assay, control variables, process and record information and interpret results. Never count out human error entirely and implement procedures that can help reduce the likelihood of human error.

Faulty Device

Since the consequences of a failed drug test can be so severe t here is a great deal of work and investment that goes into quality control for drug test devices. Still there are always some faulty tests or batches of tests that slip through.

If you have several tests in a row give unexpected results you should consider that the tests may be faulty. It’s very cheap and easy to use a 2nd drug test if a subject says that their results aren’t accurate.

Our drug test cups are designed to alert the user when there is a problem with the device itself. The control line can alert you to tampering, a faulty test and some forms of improper collection.


invalid drug test result
Any test that does not show a control line is invalid and can indicate anything from a faulty test to tampering.


Keep in mind that a 12 panel drug test is actually 12 individual tests; most of the time a faulty device means only one of the strips is faulty. A certain percentage of faulty tests is expected in this industry, which is why we offer a 100% satisfaction guarantee that covers any faulty devices and any additional tests you use to troubleshoot a possible faulty test.

Other Anomolies

There are times when all of the devices are functioning properly, everyone did everything they were supposed to do and a sample is valid in every way and still there is a false negative drug test result.

The Hook Effect

One rare cause which has been addressed by manufacturers in recent years is the “hook effect” where there is so much of a drug present in the urine that there are no more binding sites left on the antibody. This can cause a lower apparent level which can lead to a negative result if it’s below the cutoff level.

Drug Degradation

One benefit of using a drug test cup is that the receptacle is also the test. There is no lapse in time between collection and testing. In a busy medical office technicians may become distracted or intentionally multi task when working on test results.

When shipping to a lab it could be even more time between collection and testing. The time in transit and any time that the shipment sits in the lab without proper refrigeration is more time for the sample to naturally degrade.

Most metabolites are stable for the short periods common in drug testing, but others are not stable especially when subjected to temperature changes or extremely high temperatures.

One example is 6-monoacetylmorphine (6-MAM), a metabolite of heroin. In the body heroin is metabolized to 6-MAM, which then metabolizes to morphine.  6-MAM lacks stability, is subject to in vitro hydrolysis and also continues to metabolize into morphine even after the urine leaves the body. One study showed that within 7 days at room temperature a urine sample that was positive for 6-MAM had hydrolyzed completely into morphine.

Limiting False Negatives on Drug Tests

Understanding that a false negative is a possibility and the likely causes is the first step in stopping them. Collecting and storing data can be an important part of investigating unexpected or suspicious results.

With enough knowledge and proper analysis many drug test results that are contradictory to expectations can be reconciled and explained. Here are some other tactics you can use to limit the likelihood of false negatives in your drug testing program.

  • Institute procedures and policies to combat water loading and adulteration
  • Use a 12 panel drug test to cover many of the synthetic and semi-synthetic opiates
  • Understand the cutoff levels and detection times for the tests you use
  • Institute policies and procedures that decrease the likelihood of human error
  • Report faulty tests to the manufacturer or retailer



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What is a False Positive on a Drug Test?

False Positive drug test

When people fail drug tests they often claim that it was faulty or there is some mistake. In most cases this is a ruse and the individual is dirty, but false positives on drug tests are real and many innocent patients have failed a drug test only to be vindicated later on by a confirmation. So what exactly is a false positive on a drug test and when is it just another attempt at subverting drug test results?

What is a False Positive on a Drug Test?

A false positive is a drug test result that is not accurate due to another substance mimicking the target metabolite.

The majority of false positives are caused by medications, foods, and supplements that are well known to cause false readings on a drug test.

Some people have gotten a false positive from second hand marijuana smoke. The most common false positives are for benzodiazepines, amphetamine, methamphetamine, marijuana and opiates.

A presentation given at the American Psychiatric Association’s annual meeting in 2010 by a researcher at the VA Medical Center in Black Hills South Dakota, Dwight Smith,  5 to 10 percent of all drug tests result in false positives and 10 to 15 percent result in false negatives.

My anecdotal research at a healthcare facility where I tested hundreds of patients each month did not support these high numbers, but we did experience a 1 to 3 percent occurrence of false positives.


CBD products come in many varieties, some have had all traces of THC removed entirely and some have not.


Most studies show that second hand smoke from marijuana and crack cocaine do not cause false positives but there have been anecdotal cases. The growing popularity of CBD products and confusion about which products contain trace amounts of THC have cause some false positives.

Many drugs have multiple identified metabolites and different immunoassays and equipment use different technologies to bind antibodies. The regeants in multi-drug test cups are generally the most stable and prominent metabolites of each drug.

Some substances will cause a false positive on a specific test under specific circumstances, but will show as negative when retested for different metabolites or using different equipment.

Legitimate false positives are rare unless a patient is prescribed a drug that is well known for causing false positives.

What Should testing Programs Do About False Positives?

Always acquire a thorough list of all the patient’s prescription, over the counter and herbal medications prior to testing. Interview the patient to find out if they drink energy drinks or eat any products that are known to cause a false positive.

Discuss adherence to medications and instruct them about how much water to ingest prior to testing to keep from diluting a sample.

A good practice is to ask an individual that just failed a drug test if they are positive for the substance. Encourage an honest answer and let them know that lying about it will only damage their desired outcome. Many people will admit to a mistake.

Always send contested drug test results to a lab for confirmation. Let the individual know that their sample will be sent to a lab that can confirm exactly what substance triggered the positive result.


Lab Drug Testing Instrument
This Gas Chromatography / Mass Spectrometry instrument combines the two techniques to give the most accurate analysis of a urine sample. By Polimerek – Own work, CC BY-SA 4.0,


When you receive the results back schedule a consultation with the individual and give them another chance to admit to their drug use before revealing the lab results.

Many courts have started programs where criminals that are alcoholic are given home incarceration on non-violent charges if they install a phone that has a breathalyzer built in. Probationers and prisoners that sign up for these programs agree that even if a positive reading comes from using mouth wash that is doesn’t matter and they will be violated as an offence.

A lot of our customers send all positive tests to a lab for confirmation, but also make decisions for care and treatment based on the results of the instant drug test.

Always instruct your clients that false positives are treated as a failed test until a lab returns the confirmation results and it is their responsibility to educate themselves about substances that could possibly affect their test results.

Things That Can Cause a False Positive on a Drug Test

One study found adulteration from household cleaning products H202 and Joy detergent caused false positives for benzodiazepines and sodium bicarbonate caused extremely high pH levels.

One study found that gentle baby soaps Johnson &Johnson, CVS Nighttime Baby Bath, Aveeno Soothing Relief Creamy Wash, and J&J Bedtime Bath caused false positives for THC for infants being tested due to their mother’s suspected drug use.

Since drug testing is used so frequently in so many applications many organizations conduct studies about false positives. Still there are so many substances humans ingest and interact with that we couldn’t possibly identify them all.

Below is a list of medications and other substances that are known to cause false positives in urine drug screens. Some will often cause an inaccurate result while others almost never do.

Once a possible cross contamination is identified use multiple confirmation methods and research the history of that medication in causing false positives. Most of these medications were identified through scientific research, but a few are from anecdotal observations at medical facilities.

Marijuana (THC) False Positives

In a study conducted to find if second-hand marijuana smoke would cause a false positive 3 non-smokers were exposed to 8 marijuana smokers who smoked 32 joints in total in a 10×10×8-ft enclosed room. No samples from the nonsmokers exceeded the federal mandated threshold. However marijuana has increased in potency since this study.

The metabolite of THC is metabolite 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH). Even though excessive intake of several substances have caused a false positive for THC, the only drug that is likely to cause a false positive is Efavirenz (Sustiva). Other known false positives are very unlikely.

  • Ibuprofen (Study)
  • Hemp Seeds
  • Efavirenz (EFV, Sustiva)
  • Ibuprofen
  • Naproxen
  • Niflumic Acid
  • PPIs (Omeprazole)

Cocaine False Positives

In a study to find if being exposed freebase crack cocaine vapors would cause a false positive, 6 volunteers in an 8×8×7-ft enclosed room were exposed to 200 mg freebase cocaine vapor; none of their urine samples exceeded the federal threshold.

Individuals that work in a jobs such as law enforcement and medicine that handle cocaine are at risk for testing positive. Cocaine can be absorbed through the skin.

A study of crime lab technicians showed 33% of subjects tested positive after analyzing solid dosage forms of cocaine. Levels in two criminologists working with large amounts of cocaine in a small room were measured up to 278 ng/mL when wearing a face mask and gloves and up to 1,570 ng/mL when wearing gloves only.


Half Kilo Cocaine
Crime labs sometimes process vast amounts of cocaine. Samples are taken from several locations of a brick to confirm the composition and purity of the evidence.


In a study of physicians administering cocaine to a patients, one physician in the group not wearing gloves had a positive test with 53 ng/mL of the cocaine metabolite in his test eight hours following exposure. Results were negative in the group wearing gloves. Another physician in this study was asked to handle cocaine for two minutes and wait 15 minutes before hand washing every two hours. This physician had a positive test of 245 ng/mL 18 hours after exposure.

Many public surfaces have been shown to be contaminated with cocaine. An analysis of 234 banknotes from 18 different US cities found that 90% contained traces of cocaine. 85% of bills in Canada had traces of cocaine and 80% of bills from Brazil. They contained up to 2,350 micrograms.

Scientific studies have found no evidence that Lidocaine or norlidocaine can cause a false positive on standard cocaine tests, but there is anecdotal evidence it is possible.

  • Coca Tea

Opiates False Positives

In 1998, the federal government increased the threshold defining a positive screen for urine morphine and codeine from 300 to 2000 ng/mL to reduce spurious reports of opiate-positive tests from poppy seed consumption.

Synthetic and semi-synthetic opiates are sometimes detected in an opiate drug test, but sometimes are not. One study found that oxycodone was detected in 12% of opiate immunoassay tests.

Given this inconsistency separate tests have been developed for semi-synthetic opiates oxycodone, hydromorphone, oxymorphone, levorphanol, buprenorphine and synthetic opiates fentanyl, methadone, propoxyphene, meperidine, tramadol, pentazocine. The most common pharmaceutical opiates are included in some multi panel tests while others must be performed separate.


Poppy Seed Muffin
Poppy seed muffins caused so many false positives in the 1990s that the NIDA introduced a new cutoff level for Opiates.


  • Poppy Seeds
  • Codeine
  • Dextromethorphan (Robitussin, Delsym)
  • Dihydrocodeine
  • Diphenhydramine (Benadryl, Advil PM)
  • Levofloxacine
  • Ofloxacine
  • Naloxone
  • Pentazocine
  • Quetiapine
  • Rifampicin
  • Doxylamine
  • Fluoroquinolone

Methadone False Positives

  • Tapentadol
  • Verapamil
  • Cyamemazine
  • Creatinine
  • Doxylamine
  • Quetiapine (Seroquel)
  • Thioridazine
  • Diphenhydramine
  • Clomipramine
  • Chlorpromazine
  • Levomepromazine

Buprenorphine False Positives

  • Codeine
  • dihydrocodeine
  • Amisulpride and sulpiride

Benzodiazepines False Positives

  • Oxaprozin (Study)
  • Sertraline (Zoloft)
  • Efavirenz (EFV, Sustiva)

Amphetamine False Positives

  • Pseudoephedrine (Sudafed)
  • Phentermine (Adipex)
  • Dimethylamylamine (DMAA)
  • labetalol
  • Bupropion (Wellbuturin)
  • Chlorpromazine
  • Metformin (Glucophage)
  • Ofloxacin
  • Promethazine
  • Trazodone
  • Fluoxetine (Prozac)
  • Methylphenidate (Ritalin)
  • Vicks Inhaler

Methamphetamine False Positives

  • levomethamphetamine
  • Metformin (Glucophage)
  • Fluoxetine (Prozac)
  • Labetalol
  • Methylphenidate (Ritalin)
  • Vicks Inhaler

Tricyclic Antidepressants (TCA) False Positives

Tricyclic Antidepressants replaced PCP on many multi drug screens because so many TCAs cause a false positive for other drugs. Having the TCA strip on your multi-panel drug test can help identify cross-reactions with other drugs.

  • Seroquel (quetiapine fumarate)
  • Trileptal (oxcarbazepine)
  • Benadryl (diphenhydramine)
  • Flexeril (cyclobenzaprine)
  • Thioridazine
  • Thorazine (chlorpromazine)

Barbiturate False Positives

  • Ibuprofen
  • Naproxen

PCP False Positives

  • Venlafaxine
  • Tramadol
  • Dextromethorphan (Robitussin, Delsym)
  • Doxylamine

LSD False Positives

  • Ambroxol
  • Ergonovine
  • Lysergol
  • Amitriptyline (Amitril)
  • Diltiazem (Cardizem)
  • Fluoxetine (Prozac)
  • Labetalol
  • Methylphenidate (Ritalin)


Additional Sources:

False-Positive Interferences of Common Urine Drug Screen Immunoassays: A Review
Alec Saitman, Hyung-Doo Park, Robert L. Fitzgerald
Journal of Analytical Toxicology, Volume 38, Issue 7, September 2014, Pages 387–396

Analysis of the cocaine metabolite in the urine of patients and physicians during clinical use
Bruns AD, Zieske LA, Jacobs AJ.
Otolaryngol Head Neck Surg. 1994; 111: 722-6

Occupational exposure to cocaine involving crime lab personnel
16. Le SD, Taylor RW, Vidal D, Lovas JJ, Ting E. .
Journal of Forensic Science. 1992; 37(4): 959-68.


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Can Drug Tests Detect Gender?

Can a Drug Test Detect Gender

We’ve all heard the stories of a man bringing his wife’s urine to cheat on a drug test and when he asks the doctor about his results the doctor responds “well you’re clean on drugs, but did you know you were pregnant?”. Can drug tests detect gender, or is this an urban legend that is an entertainment trope?

Can drug tests detect gender?

This is actually a complicated question with many aspects. In the simplest terms a drug test itself cannot detect gender. A drug test only tests for the presence of specific metabolites associated with a specific drug.

However urine tests are widely available that detect hCG (human chorionic gonadotropin), a hormone that is produced by the placenta of pregnant women. Many of our clients have a need for testing women for pregnancy because the type of treatment and care changes for a patient that is pregnant. It is relatively cheap to add an hCG strip to testing.


hCG Pregnancy Test
A pregnancy test detects levels of hCG in a woman’s urine. The placenta starts to release hCG as early as 14 days after fertilization.


In cases where drug tests are sent to the lab a gas chromatography and mass spectrometry instrument breaks down the sample into all its components. For confirmations a lab technician will focus on the analyte associated with the positive test strip, but all of the compounds are identified. A high level of hCG would be recognized fairly quickly.

So it is true that drug testing would identify pregnancy in cases when providers test for pregnancy or samples are sent to a lab. The assays found in drug test cups and used in laboratory immunoassay tests do not detect hCG though.

What Are the Differences in Men and Women’s Urine

In the rare case a lab technician or medical review officer suspects a subject has used a urine sample from someone of the opposite sex the sample can be put through additional analysis to support their suspicions. Even though a drug test itself cannot determine gender, other tests can indicate gender.

The biggest differences in each sex’s urine are trace hormones, but there are indicators that may cause a lab technician to become suspicious and investigate further.


  • Women’s urine can contain hCG (the analyte used to detect pregnancies).
  • Women’s urine can be contaminated by blood during menstruation.


  • Men process alcohol differently. Higher concentrations of dehydrogenaze are present after consuming alcohol.
  • Men have higher muscle mass which can increase creatinine levels.
  • Male samples can contain traces of sperm or pre ejaculate, however females can too for 8-12 hours after sex.

Foreign matter such as blood and semen are good indicators of gender, but are far from definite because men can have blood in their urine and women can have male semen in their urine after sex.

The easiest hormone to identify a person’s gender in urine is testosterone. Men produce less testosterone as they age, but will always excrete significantly more testosterone in their urine. Marijuana has been shown to suppress the production and secretion of testosterone and other androgens.  A study conducted by the Worcester Foundation for Experimental biology found that men excrete 28-250 μg of testosterone in their urine, while women excrete 2.4-8μg.

Testosterone Levels in Urine

Sex / AgeAVG Testosterone Levels
Male 18-28171 μg (range 65–250)
Male 30-3589 μg (range 45–150)
Male 42-5581 μg (range 28–159)
Female 23-376 μg (range 2.4–8)


Can Drug Blood & Hair Drug Tests Detect Gender?

It is almost impossible to adulterate or substitute hair or blood samples during a drug test because a subject has to physically present themselves to have samples taken. A technician will confirm the identity of the subject at the time of sample donation. Any anomalies that indicated a different gender would be investigated as a health issue instead of possible tampering.

However, the same hormones that are present in urine are present in a person’s blood, and DNA from human hair can be used to determine a person’s gender.

Hair samples can give an indication of gender simply by the length and treatment when examined under a microscope, but nuclear or mitochondrial DNA would be needed to determine gender with a hair sample definitely.

Considerations When Testing Different Genders

Even though the basic mechanisms of how a drug test works is the same whether you are testing a male or female, there are some differences you may want to account for. For example women process alcohol slower than men. It would be easier for a female to have some drinks at night and still have alcohol passing through their system the next morning.

Another consideration is that women have a much higher body fat percentage than men. A healthy middle aged male has a body fat percentage of 20% while a healthy female of the same age has a body fat percentage of 30%. Drugs or metabolites that bind to fatty tissues can be detected longer in an individual with a higher body fat content.


GenderBody TypeBF % Age 20-39BF % Age 40-59BF % Age 60-79


This doesn’t mean that a woman that you should alter results for females, but there are many instances when this knowledge is useful. For example after a failed drug test you can expect women to have a slightly longer detection time for drugs that have an affinity for fatty tissue. It can help with scheduling retests, confirming patient statements, and advising clients about detection times.

Will You Get Caught if You Use Urine From the Opposite Sex to Cheat a Drug Test?

Using urine from the opposite sex to pass a drug test will go unnoticed in the vast majority of drug screens because assays only detect the metabolite they are designed for. A male using a pregnant female’s urine would increase the likelihood of being caught because of the hCG content.

However, you are much more likely to be caught  substituting urine by a witness during screening, a cold temperature strip, suspicion from staff, or a number of other discrepancies that are present when you substitute someone else’s urine for a sample.











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Home Drug Test vs. Lab Drug Test: What’s the Difference?

home drug test vs. lab drug test

What is the difference between a home drug test vs. a lab drug test? A lot of customers assume that when a they go to a physical location to take a drug test that it’s more accurate. That’s not always the case, but there are some differences between a home drug test vs. lab drug test.

Home Drug Test vs. Lab Drug Test

Many organizations use home drug testing kits that are CLIA waived because lab costs are so high and so any employee can administer the test. They are relatively accurate and give results within a couple minutes. Usually positive tests are then sealed and sent to a lab for confirmation. Laboratories charge by the drug so it is much cheaper to confirm the presence of 1 drug than it is to test for 12 drugs using complex laboratory equipment.

Other organizations that run a lot of drug tests and have a high rate of failure send all their tests to a lab. Some facilities will even build their own lab.  Usually the cost of lab testing is subsidized in some way (either the customer pays for it or insurance pays part of the cost). Medicare and most insurances will only pay for 1 type of drug test per visit so they will not pay for a standard 12 panel cup test and a confirmation.

Home Drug Testing

Drug Testing you do at home will generally use a cup or cassette with different strips for each drug. The strip contains reagents which is the scientific term for compounds that react to metabolites produced by the drug in your body.

When you perform a drug test with a cup like our 12 Panel drug test at home you are testing for a chemical reaction between the reagent on your strips and a known quantity of metabolites in the subject urine. It’s almost like a small science lab in your house!

The biggest difference between a test that is sold to the public is whether or not it is CLIA waived.

CLIA waived means that the FDA has determined that the test is simple and accurate enough to be performed by an untrained person with a simple set of printed instructions.

Drug tests that you can use at home are considered qualitative and presumptive, meaning that they cannot tell you exactly how much drugs are present in the sample and that a positive result means that the donor likely used drugs recently.

Lab Drug Testing

Drug testing at a lab can be accomplished a number of different ways. In some cases a lab may used the same type of reagents that are used in home drug tests to do testing. They may or may not use CLIA waived tests because their technicians are likely certified in forensic drug test analysis.

Usually it is assumed that if someone sends a sample to be tested at a lab that they will at the very minimum use a presumptive drug testing method that is interpreted with the use of an instrument. This usually means they are using a drug test much like ours that is inserted into a machine that reads the results. This step takes out human error and subjectivity.

The primary reason to send a sample to a lab is to get a confirmation that uses imunoassay, mass spectrometry or chromatography. Some of these instrument chemistry analyzers are capable of detailing the quantity of metabolite in the sample. You can make deductions with this information (such as the subject is a light user or the subject had not used that day).


Immunoassay is basically the same method used by a home drug test. A reagent that binds to the analyte is mixed with the sample and the contents are measured. A home drug test has the reagents configured in a manner that is easy to use and it’s calibrated to variables determined at the time of manufacture.

An immunoassay run in a lab can be much more detailed. The sample can have its components separated to make the reagents bind to the analytes easier. The reagents can be added multiple times to make sure nothing is missed. Each test is calibrated at the time of testing to a control solution to account for variables.


A typical Immunoassay test.


In the home drug test the reagent uses a control and detection line as a signal. In a lab performed immunoassay the signal can be a number of things. The most common is linking a chemical that changes color when the reaction takes place. Other more accurate tests use radio isotopes that can be measured precisely with additional instrumentation.


Chromatography & Mass Spectrometry

With mass spectrometry a sample is bombarded with electrons which separate the sample into ionized fragments. The components sometimes separate, but even if they do not they can still be measured by an instrument capable of detecting charged particles. The instrument cycles through an intensity spectrum which correlates to mass; the results are recorded on a graph and correlated to known masses of molecules that are being detected.

Chromatography makes use of a fluid to separate a substance into its components. Various constituents travel through the liquid at different speeds causing them to separate. This is called the mobile phase of chromatography. A structure or chemical is used to stop the component particles in a stationary position. Chromatography got its name from the different colors created by the constituent particles of plants.


Lab Drug Testing Instrument
This Gas Chromatography / Mass Spectrometry instrument combines the two techniques to give the most accurate analysis of a urine sample. By Polimerek – Own work, CC BY-SA 4.0,



The most definitive laboratory test for drug testing uses a combination of gas chromatography with mass spectrometry to first separate and then accurately measure the metabolites present in a sample. By combining gas chromatography with mass spectrometry a lab technician can get a definitive measurement on the quantity of metabolites in a sample. While this testing is more accurate, it’s also very costly especially if testing for multiple drugs. Most confirmations a lab will only test for drugs that were indicated positive by presumptive testing.

Which is Better?

The bottom line is that testing done with experienced technicians using expensive equipment in a controlled laboratory is more accurate. You just need to make sure than when you pay hundreds of dollars for complex testing using expensive tools that that’s the kind of testing you’re getting.

The accuracy of a CLIA waived test cup is so good though that the added cost isn’t justified in most cases. When it comes to a home drug test vs. a lab drug test, in most cases a home drug test is the right tool for the job. Laboratory drug tests are always available though if you need a confirmation, need the presence of drugs quantified or need the most accurate option. The cost of most drug tests is so little that they make a great option for a transport container, so even if you opt to have all drug tests sent to a lab you could have an immediate presumptive result with a drug test cup.

For most uses a home drug test is the best option considering price, accuracy, purpose and immediacy.