Does Taking Aspirin to Pass Drug Test Work in 2024?

Daniel Miller avatar
Daniel Miller, Ph.D, Drug Testing Specialist

Last updated on Jan 13, 2024

Aspirin has for long been touted as a remedy for passing a test. There are two sides to this. The good news is that it actually works.

Several scientific research pieces prove that taking aspirin to pass drug tests may interfere with the immunoassay signal, thereby leading to a false negative for THC. On the other hand, you are not always guaranteed to beat the test. It’s a fifty-fifty situation.

All in all, this article will explain how to pass a urine drug test using aspirin and scientific evidence.

How to Use Aspirin to Cheat a Urine Drug Test

Why Does Aspirin Cause False Negative Drug Test Results

There lacks concrete evidence of how aspirin helps in creating a false negative so far. However, forum buddies who’ve used this method successfully have all sorts of explanations.

The most general suggestion is that aspirin masks the drug metabolites in urine, thereby making them undetectable in tests.

Another suggestion is based on salicylic acid – the active ingredient in aspirin. This school of thought claims that when aspirin is ingested, the salicylic acid is absorbed into the bloodstream, where it burns off the THC metabolites floating in the blood.

This minimizes the amount released into the urine and is later diluted below the cut off level through dilution.

Still, others believe that aspirin directly affects the testing equipment, thereby faulting its performance. This leads to a forced negative.

Whichever claim is true, several research studies show that aspirin can help you skirt the test and skew the results to your favor.

Scientific Evidence

A 1994 research study published on National Institutes of Health wanted to investigate whether ingesting aspirin decreases signal in EMIT assays during a urine test for benzoylecgonine (metabolites released into the urine after ingestion of cocaine).

The researchers were driven to carry out this study after realizing that most of the urine samples sent to their labs for analysis around that time had abnormally lower rates of absorbance changes.

For clarity purposes, the absorption rate in urinalysis is used to determine the number of drugs absorbed into the body, specifically at the site of absorption. However, since it’s almost impossible to access the receptor sites where drugs are absorbed inside the body, researchers measure the drug metabolites’ concentration in body fluids, including urine and blood plasma.

In the Emit d.a.u method, the absorption rate is first determined by determining a cutoff concentration (also known as a low calibrator). During the test, if the observed signal goes beyond the cutoff signal, the urine sample is considered positive for the drugs tested.

On the other hand, if the signal is lower than the cutoff, it is considered negative for the tested drugs.

cuttoff levels

As I have mentioned, these researchers observed that several urine samples reproduced a negative bias. Upon further experiments, they realized that most of these samples had salicylate (components of aspirin) concentrations.

Thus, they wanted to determine whether the salicylate components were responsible for the negative bias.

To do this, the study involved 6 subjects (5 males and 1 female) with a history of taking cocaine. They were required to collect one urine sample each before ingesting 4 x 325mg aspirin tablets and then a sample every 2 hours up to 20 hours.

using aspirin to pass drug test absorbance chart

40 urine specimens were taken for analysis, and the results were plotted on a graph. According to the results, 20 of the samples showed a negative absorbance rate <-4mA/min. On the contrary, results from 100 subjects who didn’t take cocaine or salicylates had an absorbance rate of <-1.05mA/min, except 2 who had <-4Ma/min.

Effects of urine salicyl ate on other Emit assays.

Using seven additional Emit d.a.u. assays-amphetamines, barbiturates, opiates, benzodiazapines, phencycidine, propoxyphene, and tetrahydrocannabinol we measured four urine specimens with salicylate contents ranging from 0 to 100 mg/dL obtained from one of the volunteers who ingested aspirin.

Reduced signals (mA/miii) were observed in all cases, paralleling the increased salicylate concentrations in the urine specimens.


Proving that The Salicylate Compounds Caused the Negative Bias

The researchers went ahead and wanted to determine whether the salicylate compounds were responsible for the negative bias.

To do this, 6 other drug-free subjects ingested 4 x 325 mg aspirin pills and collected urine samples at intervals of 2 hours. The results were plotted in a graph of the delta absorption rate against time.

It was observed that the maximum salicylate concentration corresponded directly to the maximum negative absorption rate.

This is a clear indication the salicylate compounds might have caused the negative bias in the other tests.

Negative biases observed for other Emit d.a.u. assays after salicylate ingestion lead us to conclude that the ingestion of therapeutic doses of aspirin may cause false-negative results for drug screens in urines by this technology.

Frequently Asked Questions

When To Take Aspirin For A Drug Test?

Take two aspirins six hours before the drug test. Don’t take the two pills simultaneously, but give at least thirty minutes between each pill for safety and health purposes. Then take two more, two hours before the test. Drink as much water as possible, but don’t overdo it as much to damage your health. Urinate as many times as possible before the drug test.

How Well Does Aspirin Hide THC On A Drug Test?

It has been scientifically proven that aspirin can make a urine test somewhat more susceptible to a false negative. However, this is limited only to EMIT tests or Enzyme Multiplied Immunoassay Technique.

How Aspirin Effect Drug Test For Alcohol?

Aspiring contains chemical compounds that can mask contaminants such as alcohol found within the urine. As a result, there is a pretty good chance of having a false negative drug test.

Will adding salicylic acid directly into the urine samples with cocaine have similar effects?

The researchers also wanted to determine whether adding aspirin directly into the urine sample would yield similar results. To do this, they added salicylic acid to urine samples from 4 individuals: 1 without benzoylecgonine (BE) and 3 with BE.

Interestingly, adding salicylic acid directly into the urine sample did not yield the same results. The researchers noted that the salicylic acid must be physiologically metabolized to produce a negative bias.

Will taking aspirin to pass drug test have similar effects when used on other EMIT assays?

To determine whether salicylic acid would have similar effects on other Emit assays, urine samples were taken from subjects who had used opiates, amphetamines, benzodiazepines, phencyclidine, barbiturates, propoxyphene, and tetrahydrocannabinol (THC).

Reduced signals were detected in each sample. Therefore, it was concluded that taking an aspirin a few hours to the test may decrease the signal on these EMIT technologies.

How much aspirin do you need to take to pass a drug test?

According to the researchers, the subjects tolerated the four 325 mg pills of aspirin. Notably, according to the graphs, the subjects took a different time to reach the salicylate concentrations’ peak. This means that individuals require varying amounts of salicylic acid and time to reduce the signal.

The researchers also add that medical texts show that daily doses of up to 10 (325 mg) pills of aspirin are prescribed for patients suffering from rheumatoid arthritis.

Unfortunately, there isn’t a way of determining exactly how many tablets one would need to take to falsify a test.

Do People Pass Urine Tests Using Aspirin Today?

Well, scouring a few internet forums, you’ll come across lots of people who have passed the test with flying colors using this method. However, there are still others who fail miserably.

It’s over a decade since it became evident that aspirin can be used to falsify a test. Needless to say, there have been a lot of changes in EMIT technology, and it’s now possible to detect salicylic acid in urine.

Even worse, most labs will still detect the drug metabolites regardless of the presence of aspirin ingredients in the urine or not.


Aspirin has the potential to help you beat a test. But there’s also a high risk of failing. If you are desperate to pass the test, then the best idea would be to combine this ‘magic pill’ with the dilution method.

The dilution method is the easiest and surest way to beat a urine drug test. The best part of this method is that it can be used as a same-day solution and won’t cost you much.

However, as we have indicated in another article on how to pass a urine test using water, this method has some technicalities and requires expertise. Among other things, you’ll want to consider your Lean Body Mass besides keeping a close eye on your urine’s Specific gravity and creatinine levels.

100% Success Rate for Passing Drug Tests!

Clear Choice Sub-Solution is the perfect solution for passing a drug test. It contains a clean synthetic urine that is biocide free and completely undetectable.

It also comes with their patented heat activator formula that raises the urine’s temperature to normal body temperature within seconds, so you don’t need to worry about having to heat it up yourself.

Furthermore, the standard size container makes it easy to conceal, and it is unisex, so it can be used by both male and female users.

The information on this website about detox products and synthetic urines is for educational purposes only. We do not endorse or condone their illegal use. Always consider the laws in your area and the potential legal consequences. Consult with a healthcare professional before using any products. Your responsibility and well-being are paramount.