How long are drugs in one’s system?

Drugs have certain “detection windows”—the amount of time after ingestion during which evidence of their use can be detected by a drug test. Though it might not be wise to publicize detection windows and invite employees who may use drugs to push their limits, when implementing drug testing, it is important to understand them. For instance, alcohol is absorbed and eliminated more quickly than other drugs. This is why post-accident testing procedures often require testing for alcohol to occur within two hours. Other drugs are eliminated from the system at different rates and thus detectable for different periods of time, often long after the drug's effect has worn off. The following are estimates of the length of time that certain drugs are detectable:

Alcohol – 1 oz. for 1.5 hours

Amphetamines – 48 hours

Barbiturates – 2-10 days

Benzodiazepines – 2-3 weeks

Cocaine – 2-10 days

Heroin Metabolite – less than 1 day

Morphine – 2-3 days

LSD – 8 hours

Marijuana – casual use, 3-4 days; chronic use, several weeks

Methamphetamine – 2-3 days

Methadone – 2-3 days

Phencyclidine (PCP) – 1 week