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Passing A Drug Test

Drugs of different chemical structures leave (or are excreted) from the body by different routes after they have been absorbed and distributed.

In humans, the major route that drugs take to leave the body is through URINE. Drugs, once in the bloodstream, travel to the kidneys where they are absorbed and filtered and then the remaining or residual blood, water and substance travel to the bladder and then leave the body through urination.

Common questions regarding drug testing:
What is the difference between urine concentrations of substances and blood concentrations of substances?
What is the best way to test for Marijuana?

What about detecting drugs other than Marijuana using urine testing?

How do individuals attempt to hide or get rid of drugs (drug metabolites ) in the body?
How can someone successfully eliminate or clean the urine sample to avoid detection?
Can someone pass a drug test by diluting the sample?
Can someone pass a drug test by using diuretics?
How are drug tests contaminated to give false results?

Comparison of testing procedures
Length of detection period for illicit drugs

In-home drug testing kits are available through our online store.

Please note:

What is the difference between urine concentrations of substances and blood concentrations of substances?

The differences between urine concentrations and blood concentrations of substances are determined by:

1. the chemical structure of the drug
2. the pH (relative acidity) of the urine - which can vary chemically by disease conditions after administering certain drugs.
3. the absorption process by the kidneys which vary among
4. and the time that passes between formation of urine concentration stored in bladder and emptying of bladder.

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What is the Best way to test for Marijuana?

THC (delta 9--tetrahydrocannabinol) is the active ingredient found in Marijuana. THC is fat-soluble. When smoking marijuana, THC is distributed to various body organs, especially those with high amounts of fat tissues. Thus THC is metabolized (or processed through the body) quite slowly. Therefore THC can remain in the body, being slowly released into the urine for several days or weeks - depending on how much an individual smokes, how often, the percentage of THC in the marijuana and the rate the individual metabolizes. Individuals with large amounts of fat (or obese) will eliminate THC even slower.

Testing for THC: urine (urinalysis) - a positive result may indicate either recent use or use that occurred several weeks earlier. In addition, because of the slow rate of elimination as well as other factors, a positive urine test for marijuana may have no relationship with the presence of THC in the blood. Peak blood levels of THC occur about 10 minutes after starting to smoke. Within 2 hours blood levels generally fall to low levels but may be detectable for up to 12 hours.

Therefore urine testing may be the best way to detect whether or not someone has used marijuana within a 2-4 week period.

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What About Detecting Drugs other than Marijuana using urine testing?

Most other drugs of abuse including cocaine, heroin (opiate family), phencyclidine (angel dust), amphetamines (speed)…because of their rates of absorption and metabolism (processing them through the body); can be detected in urine samples up to 72 hours after use.

Alcohol is water-soluble so it passes through the body more rapidly than most other substances of abuse. Therefore using urine testing, blood testing, or breathalyzer to detect alcohol levels, needs to be performed within 24 hours of the start of drinking or else elimination of alcohol will cause a negative test result.

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How do individuals attempt to hide or get rid of drugs (drug metabolites ) in their body?

People have been known to attempt to hide the detection of their drug use, when asked to submit a sample for urine testing by:

  • diluting the sample (adding water or liquid)
  • masking the sample (using adulterants)
  • cleaning the sample (bleach)
  • substituting the sample (using someone else's urine)

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How can someone successfully eliminate or clean the urine sample to avoid detection?

Using marijuana as an example (because it has the longest time that it can be detected in a urine sample), marijuana (THC) is absorbed in the fatty tissue and is slowly released into the blood stream, so the only successful way to avoid detection is to reduce or eliminate the fatty cells through exercise. Thus, elimination of THC from a person's urine sample takes time-- as much as 30 days.

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Can Someone Pass a Drug Test by Diluting the Sample?

Flushing or saturating the body with water or other fluids will dilute drug metabolites to produce negative results on drug tests, depending on an individual's metabolism.

Two situations can occur however where the attempt at diluting a sample will be detected by drug testing administrators.

1. Although most drug tests (urinalysis) measure PH levels
in the urine - many laboratories also measure creatine levels. The creatine levels will show if the drug test has been diluted.

2a. Diluting a sample by drinking water will also produce a clear colored urine sample with virtually no yellow urine color. Most drug test administrators assume a clear colored sample is diluted.

2b. Some individuals add a B-vitamin to add the yellow color to the urine. That sometimes works in terms of adding color to the sample but creatine levels would ultimately prove dilution.

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Can Someone Pass a Drug Test by Using Diuretics?

Diuretics will cause an individual to urinate more often.
Diuretics frequently used include:

  • coffee
  • cranberry juice
  • beer
  • iced tea
  • herbal tea
  • sodas
  • Goldenseal (an over-the-counter herbal diuretic sold in liquid or pill form).

Other products sold commercially as drug testing adulterants are:

  • XXtra Clean
  • Root Clean
  • Ready Clean
  • Ready Clean Gel Caps
  • Ready Clean Thin
  • Ready Clean for Women
  • Constant Cleanse
  • Detoxify Zone
  • PRE Cleanse
  • Detoxify

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How are Drug Tests Contaminated to give False Results?

Here are the common ways accuracy is affected when drug tests (Urinalysis) are given:

1. Contamination of specimen or container.
2. Quality of Laboratory
3. Type of tests used
4. Carelessness of Collection
5. Technician error in testing.

Deliberate Sabotage of samples for drug testing occur by:

1. Placing chemical substances under fingernails
to release into sample
2. Puncturing specimen container with a pin, allowing urine to leak out slowly during transport to lab.
3. Adding soap from restroom dispensers to specimen.
4. Replacing clean urine with contaminated sample.
5. Scooping water from toilet to dilute sample.

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Comparison of Testing Procedures

Type of test Sensitivity to contamination Availability
On-site Test Cups (immediate results) Poor Commercially sold at pharmacies or on the internet
Toxicology Screen (TLC) (in laboratory) Poor Inexpensive, available in most labs
Chemical Analysis (G C-ms) Excellent

Expensive, available in some labs

Inmmunoassay (RIA, EIA) Good Moderate cost, available in many labs, easily automated

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Length of detection period for common illicit drugs

Drug Type Detection Period
Amphetamine Stimulant 2-4 days
Barbiturate Sedative 12 hours - 3 weeks
Cocaine Stimulant 2-4 days
Fentanyl Narcotic (opioid) less than 1 hour
Heroin/Morphine Narcotic (opioid) 2-4 days
Marijuana Hallucinogen 3 days to 1 month
Methadone Analgesic 2-4 days
PCP (Angel Dust) Anesthetic 1-30 days
Benzodiazepine Tranquilizer Up to 1 week

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Disclaimer: Statements made on this web site are for educational and informational purpose only and are not meant or intended as a substitute for medical advice. Information and statements have not been evaluated by the US Food and Drug Administration and are not intended to diagnose, treat or prevent any disease or medical condition.

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Brands et al… (Editors), Drugs and Drug Abuse: A Reference Text,
Addiction Research Foundation (Toronto, Canada) 1998.

Julien, Robert, A Primer of Drug Action, Worth Publishers (NY) 2002.

Kalant, Corrigall,, Hall, Smart, (Editors) , The Health Effects of Cannabis, Addiction Research Foundation (Toronto, Canada) 1999.

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