Adulterants, false positive or false negative results. Are drug tests accurate?

What adulterants drug testing centers test?

Adulterants are substances that detect any substitution or tampering of urine. Drug Testing Centers check specimen validity by testing urine temperature, color, smell, creatinine, nitrite, pH, specific gravity and other oxidizing agents. The temperature is tested within 4 minutes after urine collection. Smell and color are checked too. Creatinine, pH, specific gravity, nitrite, and oxidizing agents are included in the cup and any result outside the normal range is retested. 


Creatinine is a chemical waste product produced by muscle metabolism. If you run a marathon or exercise excessively right before your drug testing, your creatinine will be out of normal range. Diuretics or excessive liquid drinking also cause low creatine in urine and a sign that you have been detoxing.

pH levels show acidity and alkalinity in urine. Any result outside 4.0 - 9.0 range means adulteration has occurred.

Specific gravity measures the donor/employee state of hydration and dehydration. Values out of range indicated diluted urine.

Nitrite testing is usually done to test the nitrate-reducing bacteria that causes urinary tract infection. If positive it could cause a false positive result.

Oxidants strips test for bleach and hydrogen peroxide substances.

Glutaraldehyde detects the consumption of detox products on the market that falsely claims to detox your body faster. Normal urine does not contain glutaraldehyde and a positive result means your urine was altered.

Marijuana Drug Test

What are false positive and false negative results?

False positive and false negative results are erroneous results, and re-testing is requested. If med techs suspect that your result is not accurate or tampered, your urine will be sent to advanced testing where drugs can be detected at lower concentrations and more specific than the screening cup.

All drug testing cups are tested with positive and negative controls to ensure validity, test specificity, and accuracy. False positive and false negative results are always investigated further with advanced testing.

False positive- your result is positive instead of negative due to other substances or conditions that altered the test results.

False negative- your result is negative instead of positive due to other substances or conditions that altered the test results.

False positive or negative test results may occur when the cassette is contaminated, expired, or wrong specimen and/or procedure is used.

When testing with our product, medicines or other types of drugs at 100ng/mL concentration cannot cause a false positive or false negative result (See package insert).

What can change my test result?

  • Diluted urine or adding adulterants cause inaccurate results
  • Expired cassette: check expiration before testing
  • Medicine for pain such as ibuprofen, hemp products, or other prescription drugs may cause a false positive result. Always read the manufacturer’s package insert - Non-crossing compounds. There you will find a list of substances or drugs that may interact at certain concentrations with your actual drug testing
  • Old urine; test immediately after opening the pouch
  • Storage temperature: THC cassettes should be stored between 36-86°F (2-30°C)

It is important to bring the specimen and cassette at room temperature before testing. 

When testing home drug testing kit at home make sure you follow the product insert instructions and do not take Ibuprofen, or hemp seeds products that are well known to give you a false positive THC result.


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