Methamphetamine is available in two forms: “d” and “l.” They have the same chemical formula and similar chemical properties and a drug test cannot tell the difference. MOST positive drug test results  for meth are indeed positive for methamphetamine. Most donors who have a positive test result for meth will deny it, even if they use it. However, it is possible to have a false positive for meth, and there are ways to prove it wrong.

False Positive for Meth – What You Should Do

If a donor truly believes it’s a false positive, s/he can ask for a d/l isomer test.

The “d” form is a prescription stimulant and appetite suppressant. The “l” form is available over-the-counter as the active ingredient of a specific Vick’s inhaler and is a metabolite of certain prescription medications. Both “d” and “l” forms test positive by both immunoassay and most confirmation assays.

If the donor were to claim that they had a methamphetamine positive because they used a Vicks inhaler, then the MRO would order a d/l isomer separation to determine if the drug present in the specimen is at least 80% l-methamphetamine.  If the specimen contains more than 20% d-methamphetamine, then the donor is to be considered positive for illicit methamphetamine use.

The l-form of methamphetamine  is available OTC in the Vicks and other generic nasal inhalers and the d/l isomer test can tell the difference.

D-Methamphetamine abuse is widespread. Meth labs appear nationwide in primarily rural settings, though we have had plenty of positives in urban and suburban areas.

Meth (also called meth, crystal, chalk, and ice) may be administered orally in capsules or tablets, snorted, or smoked. Methamphetamine is an extremely addictive stimulant drug that is chemically similar to amphetamine.

Further Reading about Drug Tests: