Australia Drug Testing


By Australia Drug Testing / November 10, 2023

By Australia Drug Testing / November 10, 2023

Can diluted urine give a false negative drug test?

Diluted Urine Drug Test - Australian Drug Testing

When there is excess water in the urine, it becomes diluted urine. This means it is in a low concentration, and the test may not be able to determine the presence of drugs.

Typically, you conduct a urine drug test to detect prescription and illicit drugs in the urine. During this process, you would examine the urine for certain substances or their metabolites, which the body produces after digesting the drugs.

However, neither too much nor too little water should be present in the urine. Otherwise, the drug test result may come out as diluted or invalid.

If you have a workplace drug testing program, you might wonder what causes diluted urine. The different causes of urine dilution are covered in this article, along with tips on how to obtain valid results.

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How to Detect Diluted Urine Drug Test?

A diluted specimen is a urine sample with more water than a typical specimen. Employees who are trying to cheat the drug test may submit diluted urine as their sample. However, dilution can sometimes occur by mistake or caused by an existing health condition.

Normal urine is often darker in colour than diluted urine colour. Additionally, by using measurements known as validity checks, collectors can establish whether the urine is diluted. Urine creatinine and specific gravity are among these tests.

Urine Creatinine Test

The main indicator of dilution is the amount of creatinine in the urine sample; therefore, you can’t consider the sample as urine if there is no creatinine present. Creatinine concentrations in normal samples typically range from 20 to 350 milligrams per deciliter. You define a dilute as 20 milligrams or less per deciliter.

Specific Gravity Test

You can determine a urine’s concentration by its specific gravity. It contrasts the number of drugs in the urine with the water content.

The specific gravity of typical urine ranges from 1.002 to 1.030. The specific gravity of diluted urine ranges from 1.001 to 1.003.

PH Test

Determining specific urinary properties, such as a pH test to find the presence of acidic or alkaline adulterants in urine, is one of the best methods to test for adulteration or dilution. The pH range under normal conditions should be 4.0 to 9.0. Values outside of this range can be a sign that the employee tampered with the sample.

Temperature Test

A temperature strip is also effective in checking the validity of a urine sample. For example, suppose a urine sample’s temperature is higher or lower than the acceptable range of 32 °C to 38 °C. In that case, there is a possibility that the participant may have tampered with, diluted, or substituted the sample.

Why Is Diluted Urine in Drug Tests a Problem?

A diluted drug test result might be ambiguous, making it challenging to ascertain whether the person is a drug user.

Positive and negative specimens are the two different categories.

A major issue with diluted urine in a drug test is that you may not be able to tell if an employee is using drugs, which could result in an incident that could potentially harm coworkers, clients, and the entire business.

A diluted urine test makes it difficult to tell whether a worker is consuming drugs. You may readminister the test if the result comes out as diluted urine. But this should be done in accordance with your workplace drug policy.

What Can Dilute Urine and Why?

Numerous factors can cause urine to become diluted. It’s not always because somebody is attempting to cheat the test by consuming excessive water. Instead, it might occur by mistake. Here are a few potential reasons why the test may indicate a diluted urine sample.

1. The Fluids That You Drink

Many individuals understand how essential it is to drink enough water. Therefore, it is typical for people to drink a lot of water regularly. They might have diluted urine if they consistently drink a lot of fluid.

2. Preparation of Urine Sample

There is a diuretic effect on some pharmaceutical drugs. They enhance urine output, which causes urine to become diluted and diluted urine colour. Tea and coffee are examples of beverages that are diuretics.

3. Diluted Urine From Taking Diuretics

By producing urine, the kidneys rid the body of waste. However, the kidneys may leak too much water into the urine if they aren’t functioning correctly.

4. Diluted Urine From Kidney Problems

Numerous factors can cause urine to become diluted. It’s not always because somebody is attempting to cheat the test by consuming excessive water. Instead, it might occur by mistake. Here are a few potential reasons why the test may indicate a diluted urine sample.

What Can Dilute Urine and Why?

You can establish the following rules as a urine drug test guide to avoid diluted urine:

    • Ask staff to consume fewer fluids before the procedure. If they drink lots of water before the test, the sample may come out as diluted.
    • Before providing a sample, ask them to abstain from diuretics like coffee and tea.
    • Collect the sample first thing in the morning because that’s the best time to obtain concentrated urine.
    • Take the urine sample before they start working if their employment demands them to drink frequently.
    • Randomly schedule urine drug tests to prevent employees from preparing to contaminate their samples.
    • Keep employees from bringing their personal items into the testing area since they might try to smuggle water in to dilute their sample.

What to Do When a Test Comes Back As Invalid?

First, a positive dilution drug test result indicates that the individual may have intentionally or accidentally altered the sample, and the test needs to be retaken.

If the test is invalid, it does not necessarily indicate that there were drugs in the urine sample. It simply means that either the specific gravity, creatinine concentration, temperature, or acidity of the sample was outside the accepted normal range for actual urine. An invalid test could indicate an underlying health condition, or that the sample was tampered with or substituted. 

Your drug testing policy should clearly state how you would deal with an invalid test. For example, would you demand a retest from the employee immediately or ask them to return in the next 24 hours? 


A urine drug test result may come out as invalid in cases of diluted urine. It doesn’t necessarily imply that the employee is attempting to cheat the test. To maintain their health or make sure they can pass enough urine, some people may drink a lot of water before the test. Specific drugs and kidney issues can also bring about diluted urine. 

To prevent urine dilution, limit water and diuretic intake before administering the test. You can also collect urine before work or in the early morning to obtain highly concentrated samples for the best results.