Drug Test FAQ’s

Drug Test FAQ’s. Answers to questions about drug test. Learn how to use the drug test and read the test results.

Frequently asked questions about drug test answered here.

What if I have additional questions?

Contact customer service:

  • Customer Service Toll Free 1-866-323-7336
  • Email questions to customerservice@usscreeningsource.com

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C or Control  Line on a drug test

A procedural control is included in the test. A red line appearing in the control region (C) is considered an internal procedural control. It confirms sufficient specimen volume, adequate membrane wicking and correct procedural technique.

T or Test Line on a drug test

NEGATIVE:* A colored line appears in the Control region (C) and a colored line appears in the Test region (Drug/T) next to a specific drug tested. This negative result means that the drug concentrations in the urine sample are below the designated cut-off levels for a particular drug tested.

*NOTE: The shade of the colored line(s) in the Test region may vary. The result should be considered negative whenever there is even a faint colored line.

POSITIVE: A colored line appears in the Control region (C) and NO line appears in the Test region (Drug/T) next to the name of a specific drug tested. The positive result means that the drug
concentration in the urine sample is greater than the designated cut-off for a specific drug.

INVALID: No line appears in the Control region (C). Insufficient specimen volume or incorrect
procedural techniques are the most likely reasons for control line failure. Read the directions again and repeat the test with a new test cup. If the result is still invalid, contact your manufacturer.

Faint Line on a Drug Test is still a negative result.

NEGATIVE:* Two lines appear. One red line should be in the control region (C), and another apparent red or pink line adjacent should be in the test region (T). This negative result indicates that the drug concentration is below the detectable level.

*NOTE: The shade of red in the test line region (T) will vary, but it should be considered negative
whenever there is even a faint or broken pink line.

How do the drug test need to be stored? Do they need to be refrigerated?

All drug test devices can be stored at room temperature up to the date of expiration printed on the individual foil pouch. They cannot be stored in extreme heat or cold and must remain sealed in the foil pouch until use. Refer to the drug test kit package insert for complete storage instructions.

What is the importance of checking the urine temperature strip on the drug test?

Under normal situations fresh urine will display a temperature between 90 and 100 degrees Fahrenheit on the temperature strip, if read within 4 minutes of the collection. If the temperature strip does not register, the specimen should be immediately re-checked.  To do this, collect a new specimen using a new cup (or strip). Specimens with a temperature out of range may indicate a substituted or adulterated sample.

Do instant test results hold up in court?

Instant drug tests provide only a preliminary analytical test result. A more specific alternate chemical method must be used in order to obtain a confirmed analytical result. The preferred confirmatory method is referred to as gas chromatography (mass spectrometry) or (GC/MS) . Any result taken to court must be confirmed by an SAMHSA certified Lab. We can provide lab confirmation through a SAMHSA certified Lab and MRO services. Please contact customer service for information.


  • New Account/Customer Services 1-866-323-7336
  • Email questions to customerservice@usscreeningsource.com

What is the shelf life of the drug test kits?

The on-site screening devices have a shelf life of up to 24 months from the date of manufacture. The expiration date is indicated on each individual foil pouch and can be used up until that date. Do not use products past the expiration date. Expired products should be discarded.

How do I know if the drug test is working properly?

A control line will be present if the test is working properly. If a control line does not appear, repeat the test with a new device. Insufficient specimen volume or incorrect procedural techniques are most likely the reasons for control line failure. Review the procedure and repeat the test using a new device. If further assistance is required, please contact US Screening Source toll-free 1-866-323-7336


 How do I use the drug test kits?

We offer FREE online Training.  Once you’ve completed the device training, take a quiz to test your knowledge of a specific device. If you pass, you’ll receive a Product Training Certificate. Your certificate can be printed from your computer

What is specimen adulteration?

Adulteration is the tampering of a urine specimen with the intention of altering the test results. Users of illicit drugs have attempted to defeat drug tests by adding adulterants to the sample after collection as a way to invalidate the testing procedure. Adding household chemicals such as detergents, bleach, and soaps or diluting samples by drinking large quantities of liquid are some of the creative ploys that abusers use to mask positive samples. One of the best ways to test for adulteration is to look for certain characteristics such as pH, oxidization, specific gravity, color and temperature. Many techniques have been devised for this purpose, including:

  • Eating or drinking substances that the donor believes will chemically alter drug test results.
  • Adding substances (salt, vinegar, bleach, detergent, Drano, Visine, etc.) directly to the urine sample to chemically alter test results.
  • Diluting the urine sample.  This can be done by drinking large amounts of liquid or taking a diuretic to increase urination.  Drug users may also add water directly to the specimen to lower the concentration of the drug so that it becomes undetectable by the test.
  • Substituting the donor’s specimen with someone else’s drug-free urine.
  • Color – A clear color may indicate that the sample has been watered down. Unadulterated, normal urine should be pale to dark yellow or amber in color. The sample is not be considered positive by color alone, but should be suspect for closer examination.
  • Temperature – The temperature of a urine specimen should be between 91 and 98 degrees when checked within 4 minutes of collection. Urine submitted at body temperature will exceed 90.50 degrees Fahrenheit. A specimen that fails below that range us suspect.

Drug Test Adulteration Information

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