Drug testing is widely used by employers, healthcare professionals, legal authorities, and rehabilitation programs to identify recent drug use. These tests screen for both prescription medications and illicit substances, depending on the reason for the test and the required sensitivity.

Whether you take prescription drugs or you engage in illicit substance abuse, you may wonder how long each drug is detectable in a test. The answer isn’t simple, though – it depends on the amount used, individual health factors, and the test.

What Are Drug Tests Used For?

Drug screenings are used for many purposes, from verifying the drug-free status of a potential new hire as part of a pre-employment check to drug screenings after on-the-job accidents to evaluating compliance with substance use treatment programs or law enforcement procedures.

Many drug tests screen for commonly used substances like marijuana, opioids, cocaine, and amphetamines, as well as classes of drugs.[1] The type of test can affect the detection window. Some drugs can be detected for a few hours after they’re used, while others can stick around for weeks or even months and may be detectable.

Common Drug Testing Methods

Drug tests analyze a biological sample, like urine, saliva, blood, hair, or sweat, to detect the use of drugs. Specifically, these tests look for drug metabolites, or the byproducts.

Urine testing is often used in workplace settings, such as pre-employment screening or post-accident testing, because it’s non-invasive, inexpensive, and provides quick results. Saliva testing is also convenient and can identify recent drug use. Blood testing is used primarily for medical or law enforcement testing, but it’s highly reliable.

Hair testing offers a long detection window, typically lasting up to 90 days, and is difficult to tamper with because samples are collected near the scalp and analyzed in a laboratory.[2] However, hair testing isn’t used as often because it’s expensive and has a longer detection window, which limits its usefulness in identifying recent drug use.

How Long Do Drugs Show On Drug Tests?

The effects of a drug can wear off quickly, but it takes much longer for the drug to leave your system. For example, stimulants like meth and cocaine have rapid, intense euphoria that fades quickly, while hallucinogens can have prolonged effects. In either case, the residual traces of the drug can linger long after the high goes away.

The detection windows can vary by test type and substance:[3]

• Urine can detect drug use from a few hours to a week after use
• Saliva can detect drug use from about one hour to 36 hours after use
• Blood can detect drug use for a few hours to a few days
• Hair can detect drug use for up to 90 days

Several factors can affect drug detection windows, including:

• The type of drug and dosage
• The frequency and duration of use
• Metabolic rate and overall health
• Body mass and hydration levels
• Age and sex
• Drug interactions and tolerance levels

What Is a Drug Half-Life?

The half-life of a drug refers to the time it takes for half of the substance to be eliminated from the body. A drug’s half-life helps determine how long its effects may last and how long it will remain detectable.

For example, a drug with a half-life of 12 hours will be eliminated by 50% approximately 12 hours after the last dose.[4] After 24 hours, about 25% remains, then after 48 hours, about 12.5% remains. Each 12-hour period reduces the current concentration by half until it’s eliminated.

Drugs with longer half-lives, such as certain benzodiazepines like diazepam, linger in the body longer than those with shorter half-lives, like alprazolam.

How Long Drugs Stay In Your System by Substance

Here are the estimated detection windows for common drugs based on urine, saliva, and hair tests. Keep in mind that these are general windows – different factors can affect how long a drug is detectable:[5]

• Alcohol: 10-12 hours in urine, up to 24 hours in saliva
• Amphetamines: 2-4 days in urine, up to 48 hours in saliva
• Benzodiazepines: Up to 7 days in urine, 90 days in hair
• Barbiturates: Up to 7 days in urine, 90 days in hair
• Cocaine: 1-8 days in urine, 1-36 hours in saliva
• Marijuana (THC): 1-30 days in urine, up to 24 hours in saliva
• Methamphetamine: 2-5 days in urine, up to 48 hours in saliva
• Heroin: 2-3 days in urine, up to 36 hours in saliva
• Morphine: 2-5 days in urine, up to 36 hours in saliva

Can I Clear Drugs from My System?

Pharmacy shelves and online retailers are stocked with at-home remedies or detox kits to help you “beat” a drug test or clear your body of drugs in a fraction of the time. If it sounds too good to be true, it is. These products are unreliable, untested, and possibly unsafe. Most detox products aren’t approved or regulated, so their effectiveness and safety have not been proven.

At best, you could end up feeling ill with a failed or flagged test. At worst, you could have severe and even life-threatening consequences.[6] If the detox kit doesn’t cause complications, abruptly stopping drug use to pass a drug test can. Some drugs, such as alcohol or benzodiazepines, can have life-threatening withdrawal symptoms.[7]

How to Detox from Drugs Safely

Chronic use of a drug can lead to physical dependence. Your body has adapted to the drug; it needs it to function, and if you stop, unpleasant withdrawal symptoms occur as your body readjusts. Withdrawal symptoms can range from uncomfortable or painful, like withdrawal from opioids or marijuana, to dangerous or possibly fatal, like withdrawal from benzos or alcohol.[8]

If you’re worried about a drug test, resist the urge to quit cold turkey. You’re not only making it much harder on yourself, but you can have serious complications. Medical detox provides support from healthcare professionals to monitor your symptoms, provide medication and management, and ensure you go through withdrawal safely.

Withdrawal isn’t just a problem if you’re addicted. You can develop physical dependence on habit-forming drugs even when taken as prescribed over a prolonged period. Depending on the drug, you may need a taper schedule to detox safely.

If you are addicted, detox is just the first step. You need to address the underlying causes of addiction and compulsive drug-seeking behavior with a comprehensive addiction treatment program. Otherwise, you may go through withdrawal only to relapse and start the cycle over again.

Concerned About a Drug Test?

If you have an upcoming drug test and you’re worried about your drug use, the safest and most effective way to prepare isn’t with at-home detox kits. You need professional help with medical detox and support to create a plan for ongoing recovery.