Understanding drug test cut-off levels and detection times can be confusing, especially if you are new to drug screening. This guide explains how cut-off levels work, what ng/mL means, and how detection times can vary between urine and saliva drug tests.
This information is provided for educational purposes only and is intended to help users better understand drug screening results.
What Does ng/mL Mean in Drug Testing?
ng/mL stands for nanograms per millilitre. In drug testing, this measurement refers to the minimum concentration of a substance that must be present in a sample for the test to return a positive screening result.
Each drug test uses a defined cut-off level. If the substance concentration is below this threshold, the result will show as negative. If it meets or exceeds the cut-off level, the result will show as positive.
What Are Cut-Off Levels?
Cut-off levels are screening thresholds used to standardise drug testing results. They are not designed to measure exact drug quantities or determine impairment.
Cut-off levels help reduce false positives caused by trace exposure, medication cross-reactivity, or environmental contamination. These thresholds are widely used in home testing, workplace screening, and professional environments.
Urine vs Saliva Cut-Off Levels
Urine and saliva drug tests use different cut-off levels because they detect substances differently.
Urine testing typically has higher cut-off thresholds and a longer detection window, making it suitable for historical screening.
Saliva testing uses lower cut-off thresholds and detects more recent substance use, often within hours or days.
Both methods are widely used for initial screening purposes.
Typical Screening Cut-Off Levels (Example)
Below are examples of commonly used screening cut-off levels. These values are provided for educational reference and may vary depending on the test manufacturer and intended use.
• Cannabis (THC): 50 ng/mL (urine), 20 ng/mL (saliva)
• Cocaine: 300 ng/mL (urine), 20 ng/mL (saliva)
• Opiates: 2000 ng/mL (urine), 10 ng/mL (saliva)
• Amphetamines: 1000 ng/mL (urine), 50 ng/mL (saliva)
• Methamphetamine: 1000 ng/mL (urine), 25 ng/mL (saliva)
• Benzodiazepines: 300 ng/mL (urine), 20 ng/mL (saliva)
• Methadone: 300 ng/mL (urine)
• MDMA: 500 ng/mL (urine)
