Blood concentrations for methamphetamine use as a prescribed medication are typically in the range of .02-.05 mg/L for a person taking methamphetamine prescribed for attention deficit disorder, weight loss or narcolepsy.  Drug abuse with methamphetamine yields blood levels as low as .01 mg/L and 2.5 mg/L.  Levels above 3.0 mg/L have been documented and are associated with significant risk of toxicity. Some laboratories report drug concentrations using different units such as micrograms and milliliters. Online search engines offer converters that will automatically convert units and allow for direct comparisons of levels.

As the liver attempts to clear the body of methamphetamine, 5-7% of the drug is metabolized to create the metabolite amphetamine. As a result, screening tests positive for methamphetamine can also be positive for amphetamine. Although it is possible that a methamphetamine user also used amphetamine prior to the test, the vast majority of the times, the presence of amphetamine is a simply by-product of the parent drug methamphetamine.

Amphetamine levels are lower than methamphetamine and appear later, with peak levels twelve hours following methamphetamine use. The presence of amphetamine is a marker that some time has elapsed since methamphetamine use started. Methamphetamine users can repeat drug use several times in a day and may binge over a period of days or weeks. Multiple doses of methamphetamine interfere with interpreting  amphetamine levels to estimate timing of methamphetamine use. In order to avoid a false positive test for methamphetamine as a result of prescribed stimulant medications, some employers specify that a screening test be positive for amphetamine in addition to methamphetamine.


This month’s criminal topic is the Methamphetamine Toxicology. Topics covered are:

  • What will trigger a drug screen (6/2/16)
  • Screening for Meth (6/9/16)
  • Blood Toxicology (6/16/16)
  • Detecting Meth (6/23/16)

Note: To see all posts in this topic, click here.

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