How Long Drugs Can Be Detected in Your System

drug urine test

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More employers are requiring pre-employment drug tests and developing random drug-testing policies, and the abuse of prescription drugs is reaching epidemic levels in the U.S., prompting a corresponding hike in drugged-driving incidents. The length of time drugs stay in the system has drawn more attention from employers and employees.

In addition, the window of time that drugs can be detected in chemical testing can be critical information for both law enforcement and defendants in court proceedings. But the size and shape of this window can vary significantly from person to person and drug to drug.

Variables in How the Body Metabolizes a Drug

An exact timetable for how long drugs remain detectable in urine, blood, and saliva tests is almost impossible to determine. There are many factors that can affect how an individual's body processes or metabolizes drugs.

Drug detection times can be affected by a person's metabolic rate, which can vary widely. Metabolic rates, in turn, can be affected by age and certain health conditions. The higher the metabolic rate, the shorter the time a drug can be detected in the body.

Hydration and Body Mass

Hydration levels, body mass, and physical activity affect how long drugs will be detectable. Drug detection times can be much longer for people with increased fatty tissues, because some drugs, or their metabolites, tend to accumulate in those tissues.

Drug Tolerance

If someone has built up a tolerance to a drug, it tends to metabolize more quickly. This means the length of time it can be detected in their system can become very short.

Frequency and Amount of Use

Another key factor in drug detection time is the amount and frequency of the drug's use. One-time use of a drug might be detectable for only a short period of time, whereas heavy or long-time use of drugs can be detected for extended periods. Very frequent drug use can cause concentrations in the system that can be detected for lengthy periods after last use.

Acidity of Urine

Even the acid-base balance in urine can affect detection times in urine tests. The more acidic the urine, the shorter the detection time.

Pros and Cons of Hair Testing

Hair follicle drug tests are less likely to be affected by the above factors—and also less likely to be tampered with. These tests can detect drug use for up to 90 days.

The disadvantage of using hair tests is that drugs will not show up in the hair for seven to 10 days. Also, hair tests are currently more expensive than the standard urine, blood and saliva tests in both collection and processing costs.

Why Drug Detection Timetables Are Inconsistent

Because there are so many different factors affecting the time that drugs can be visible in chemical tests, researchers have not been able to nail down an exact timetable for the detection of individual drugs using standard testing. The best they have been able to do is develop a range of time, or detection window, during which drugs might be detected.

Detection Timetables Are Estimates

While drug detection timetables can help you better understand how long drugs might be detectable in your system, it is important to remember that these numbers are estimates. Exact timelines depend on your body mass, hydration, usage, and the type of drug testing used.

These detection timetables of commonly used and abused prescription and illicit drugs were developed from sources with a vested interest in their accuracy. They include the American Association for Clinical Chemistry, the professionals that do the actual testing; companies who sell drug testing kits to employers and law enforcement; and even companies who sell products aimed at helping people beat drug tests.

A Word From Verywell

Many different factors affect how long drugs can be detected in your system. If you are concerned about a test that you will be having, it's best to look up the particular drug or medication that you are taking for more specific information about timetables of detection.

2 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. McHugh RK, Nielsen S, Weiss RD. Prescription drug abuse: From epidemiology to public policy. J Subst Abuse Treat. 2015;48(1):1-7. doi:10.1016/j.jsat.2014.08.004

  2. US Substance Abuse and Mental Health Services Administration. Treatment improvement protocol series. Appendix B. Urine collection and testing procedures and alternative methods for monitoring drug use.

Additional Reading

By Buddy T
Buddy T is an anonymous writer and founding member of the Online Al-Anon Outreach Committee with decades of experience writing about alcoholism.