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What you should know about drug tests and false positives

On Behalf of | Jan 1, 2024 | Drug Crimes

Drug tests are not foolproof, and when a person receives a false-positive result, the presence of legal substances or human error could be the source.

People in Orlando, Florida, take drug tests for a variety of reasons. They may be ordered by an employer or a school, or they may be required as part of a substance abuse treatment program. When a person’s results indicate drug use, it does not necessarily prove guilt. Learning about the types of tests and how they may be affected by other substances can prevent a positive from having a negative result.

Types of tests

According to, blood provides the most accurate results, but a test using it is invasive and not common in non-health care settings. Saliva can indicate the presence of some drugs in the system, although it is not as sensitive to all controlled or illegal substances. A person’s breath is a good medium for measuring how much alcohol is present in the bloodstream. A sweat test involves wearing a patch to collect a sample.

Urine and hair samples provide the most convenient, comprehensive and accurate results. Although a hair test is not as likely to be contaminated during collection as urine, most drug testing is done with a urine sample. Cocaine, PCP, opiates, amphetamines and marijuana may be detected by this type of test, as well as anabolic steroids. However, a hair maintains a record of drug use as it grows, so the roots may show recent substance ingestion, and the substance may even be present on the shaft 90 days after the use.

Medications that can affect results

A variety of medications could cause a person’s results to show positive when there is no presence of illegal substances. For example, diet pills and cold or allergy medications may lead to a positive for amphetamines, while ibuprofen or sleep aids could result in an indication of barbiturates in the system.

WebMD reports that a person may test positive for amphetamines or benzodiazepines if he or she is taking some antidepressants. Prescription medications that may result in a false positive for opioid use include quinolone antibiotics.

Lab errors

False positives account for between 5 and 10 percent of all drug test results, and some of these are due to human error. According to, a single test should never be used as proof of the presence of an illegal substance, and a trustworthy facility will ensure that the sample provided undergoes a second test before any results are provided.

An attorney may be able to help someone who believes the results of a drug test are not accurate to avoid a criminal conviction and other penalties.