Employers often use urine drug tests to screen for drug use in the workplace. However, diluted urine samples can sometimes lead to ambiguous or false negative results. In this blog post, we’ll explore what diluted urine is, how it can impact drug test results, common causes, and tips for preventing diluted samples.
What Is Diluted Urine?
Diluted urine is a urine sample that contains more water than normal. The concentration of typical urine ranges from 1.002 to 1.030 in specific gravity, while diluted urine will have a specific gravity of 1.001 to 1.003. Along with this, the creatinine level, which is an indicator of concentration, is also lowered in diluted samples to less than 20 mg/dL from a normal range of 20-350 mg/dL. The increased water content thus makes it hard to detect traces of drugs.
The Science Behind Urine Concentration
You might wonder how your body manages to concentrate urine in the first place. It’s a fascinating process that happens in your kidneys. These bean-shaped organs are nature’s filtration experts, working tirelessly to balance the fluids in your body.
Here’s how it works: As blood flows through your kidneys, tiny structures called nephrons filter out waste and excess water. The loop of Henle, a U-shaped tube in each nephron, creates a concentration gradient that allows water to be reabsorbed or excreted as needed. When you’re dehydrated, your body releases antidiuretic hormone (ADH), which tells the kidneys to conserve water, resulting in more concentrated urine.
Understanding this process helps explain why diluted urine can be a red flag in drug tests. When you flood your system with fluids, you’re essentially overwhelming your kidneys’ ability to concentrate urine, potentially masking the presence of drugs or their metabolites.
Diluted Urine Specimens and Their Effect on the Outcome of a Drug Test
Excess water content in diluted urine samples can result in:
- False negatives – The drugs become too diluted to be detected by the test even if the employee uses drugs. This thus makes it possible for abusers of drugs to go undetected.
- Ambiguous results – The test identifies traces of drugs but below the threshold to produce a clear positive result. Therefore, the outcome might not clearly indicate presence of drug use.
- Invalid results – The concentration of urine is too low for the sample to be carried out and, hence, should be retaken.
Common Causes of Diluted Urine
Several factors can cause an employee to present a diluted urine specimen either knowingly or unknowingly:
- Inadequate concentration – Excessive intake of water prior to the test dilutes the urine.
- Diuretic substances – The use of various medications and other products that increase the output of urination. Some very common examples would be caffeine, herbal teas and blood pressure medications.
- Kidney malfunction – Kidney disorders can hinder these organs’ ability to concentrate urine properly.
- Attempts to cheat drug test – Some employees will purposely drink too much fluid or use diuretics in a bunk attempt to pass a drug test while using drugs.
Prevention of Diluted Urine Specimen
As an employer, you can do the following to prevent such instances where you can avoid receiving a diluted urine specimen:
- Do not allow access to volumes of water prior to testing
- Test earlier in the morning, prior to the employee having a chance to drink large volumes of fluid
- Inform employees about dilution and its effects on the results
- Randomisation of test scheduling to prevent manipulation
- Identify and process diluted specimens following the guidelines
- Retest any diluted samples for validity
Diluted urine specimens can compromise the validity of workplace drug testing. However, when employers understand what can cause dilution and implement policies that help prevent it, they can increase their chances of getting a valid drug test result back. With the right policies in place, diluted urine doesn’t mean false negatives.
Photo by Anthony Cunningham for Zoom Testing
Zoom Testing is a leading UK drug testing company and a supplier of Drug Test Kits.
