August 3, 2022

Within forensic toxicology, PharmChek® has established itself as a trusted drug testing method with distinct and proven advantages over urine, saliva, or hair testing for a spectrum of drugs, including fentanyl.

Every day, our bodies excrete about 300 to 700 milliliters of insensible sweat (uncontrolled loss of water from the skin). PharmChem, the manufacturer and sole source provider of PharmChek®, engineered its sweat patch to absorb about 2 milliliters of insensible sweat each week. Any illegal substances of large molecular weight, such as marijuana, cocaine, opiates, amphetamine, methamphetamine, PCP, fentanyl, oxycodone, oxymorphone, hydrocodone, and hydromorphone, are trapped in the patch's absorbent pad and submitted to our laboratory for analysis by LC/MS/MS—the platinum standard in drug testing.

The Benefits of the PharmChek® Sweat Patch

Many proven benefits of the PharmChek® Sweat Patch contribute to its enhanced efficacy and reliability, which is why it has continued to lead the industry for more than thirty years.

Tamper Evident

The PharmChek® Sweat Patch is tamper-evident. Once removed from the skin, successfully re-attaching it is nearly impossible and is easily recognizable to a trained professional. Further, no amount of fluid consumption will hide the presence of drug compounds in absorbed sweat.

Continuous Monitoring

Unlike urine samples with a limited detection window, the PharmChek® Sweat Patch offers continuous drug monitoring—24 hours a day, seven days a week—during its seven to ten-day wear time (or up to 14 days for some wearers when paired with our optional PharmChek® Overlay). Any drug use during this window of wear time is capable of detection.

A Hygienic Alternative

The PharmChek® Sweat Patch takes only minutes to apply and remove by a trained observer and does not require the handling of urine for testing. The sweat patch is waterproof, so wearers can comfortably work out, swim, bathe, or shower during the wear time.

Other Notable Features

In addition to the reasons listed above, other notable arguments to consider the PharmChek® Sweat Patch include:

  • Variable application/removal dates
  • Cost-effective
  • Tests for parent drug and metabolite
  • Not susceptible to dilution
  • Gender-neutral
  • Proven in court

Addressing Negative Perceptions of the Sweat Patch

For as many benefits as the PharmChek® Sweat Patch reliably provides our customers and their clients, there are some negative perceptions involving the sweat patch that we are eager to address.

Risk of False Positives


Though not a widely held belief, some argue that sweat patch drug tests can yield false-positive readings.


Since 1990, courts have regularly relied on the Food and Drug Administration's (FDA) clearance of the PharmChek® Sweat Patch as an indication of its reliability.

Additionally, courts regularly cite dozens of peer-reviewed academic studies that support the accuracy and reliability of the PharmChek® Sweat Patch, and hundreds of courts have ruled the results are reliable and admissible.

According to retired Associate Justice of the United States Supreme Court Sandra Day O'Connor, the United States Court of Appeals for the Eighth Circuit recognized that "the used widely in the criminal justice system because of its perceived advantages over other forms of drug testing, e.g., its non-invasiveness, resistance to intentional adulteration, and ability to detect drug use over relatively long periods."

Finally, All PharmChek® Sweat Patches are tested at Clinical Reference Laboratory. Specimens that screen positive are automatically advanced to confirmation via LC/MS/MS, and results are reported promptly to the supervising authority via a secure, password-protected web portal or FAX.

Unlike urine testing, both parent drugs and their metabolites are stable and detectable in sweat, and both must be present (at or above the limit of detection) to be confirmed as positive.

Limits to Use


The sweat patch cannot be used on persons who have abrasions on the skin or who are excessively hairy, and in some cases, poor application and removal of the patch have hampered its effectiveness.


The ideal placement of the PharmChek® Sweat Patch is on the upper arm. If abrasions or too much hair is present in this location, the lower back or lower midriff are acceptable alternatives for application and wear.

In the rare case that an individual has too much hair to wear the patch in any of the recommended locations, they may not be a good candidate for sweat patch drug testing. However, after thirty years of testing and analysis of the PharmChek® Sweat Patch, we find that any ineffectiveness is almost always due to inadequate training or failure to adhere to training protocols.

We encourage anyone who has questions about proper wear, application, or removal of the PharmChek® Sweat Patch to contact their sales representative.

Get Started with PharmChek®

Contact us today to learn more about the PharmCheck® Drugs of Abuse Sweat Patch—the better, cleaner, and smarter option to detect drugs of abuse.