Drug testing consists of evaluating a biological sample — such as hair, urine, saliva, among others — to determine if a person has been under drug use.

If you have been required to take a drug test, you may be having plenty of doubts. In this article, we will try to clarify 3 of the most common drug testing FAQs.

1. What types of laboratory tests are used for drug screenings?

Drug screening methods vary in accuracy and time-lapse detection.The tests used for drug screening are:


This is the most common method for drug screening used in employment testing policies.

There are two types of urine drug testing:

  • Automated Immunoassay (IA). It provides quick results and it is less expensive than a GC-MS test. However, results are not always accurate, since they can show false positives or false negatives. Tests results take around 24 to 48 hours.
  • Gas chromatography-mass spectrometry (GC-MS). This test is usually done to confirm the results from an automated immunoassay test. It provides accurate drug test results since it can detect specific drugs or medicines.


Unlike urine drug screenings, blood tests can detect recent drug use — minutes of hours after intake. 

A blood test is commonly required by employers when an employee has been in a work accident. However, to order a drug screening, employers must have reasonable suspicion that the employee has been under drug use. 


This drug test can collect the biological sample (saliva) in a quick and non-invasive manner. The test detects leftover drug residues that are in the mouth, particularly in the mucous membranes contaminated by the drug. In some cases, it can detect recent drug use (within hours up to 2 days of drug intake).

To prepare for this test, you will need to avoid food or beverages for 10 to 30 minutes before the test.


Hair screening has one of the longest windows of detection for drug users — drug clues could last up to 90 days on hair samples. However, this test cannot detect drugs right after consumption.

During the test, a healthcare worker will cut from 100 to 200 hairs from either your head or body parts. Results may be ready within the following 24 hours.


There are two ways to test sweat for drug use:

  1. A healthcare worker collects a sweat sample within the first 24 hours after drug use.
  2. The subject will use a sweat patch for the next 7 to 14 days, allowing the sweat to accumulate in the patch. The patch is later removed by a healthcare professional.

This is one of the most affordable tests. However, it is not as easy to find in clinics as other drug tests.

2. How long can drugs stay in my system? 

Even if you are no longer feeling the main effects of drugs, it takes time to eliminate them from our bodies. The detection time could vary depending on:

  • How often the drug is consumed
  • Body mass
  • Hydration levels
  • Type of drug and route of administration

3. What can cause a false positive in a drug test? 

Before taking a drug test, it is important to tell your healthcare provider if you are currently taking counter medications, vitamins, or supplements; otherwise, it could affect the accuracy of your results.

Other factors that could affect your results are the use or consumption of:

  • Mouthwash
  • Poppy seeds
  • Frequently passive smoke inhalation
  • Antidepressants (Sertraline)
  • Antibiotics

We hope this clarified your doubts regarding drug testing. For further information, please reach out to Soteria Screening Laboratories. Our staff will provide further details about drug screenings or other lab procedures you may be interested in. We are here for you!









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