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 (rare, but possible) to have a false positive for meth, and labs, MROs and employers need to make sure before determining a meth positive.
Positive for Meth – What You Can Do
If a donor truly believes it’s a false positive, s/he can ask for a d/l isomer test. Some labs and MROs do the d/l isomer test automatically.
The “d” form is a prescription stimulant and appetite suppressant. The “l” form is a metabolite of certain prescription medications. Both “d” and “l” forms test positive by both immunoassay and most confirmation assays.
There are also three weight loss drugs that can pop for methamphetamine. All require a prescription. See the 2024 MRO Manual.
Examples of trade names of drugs that may produce a positive result for methamphetamine and/or amphetamine (metabolite of methamphetamine) include
- Desoxyn®
- Eldepryl®
- Didrex®
The Vicks Defense
From the above-referenced MRO Manual: “donors reporting the use of nasal inhaler products is commonly referred to as
the “Vicks defense” even though Vicks products no longer contain l-metamfetamine (l- methamphetamine).”
If the donor were to claim that they had a methamphetamine positive because of something other than meth, 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.
D/L Isomer tests are not free. Our clients are charged a $99 fee for each D/L isomer test conducted.
Another Possible Explanation
It is increasingly common for street drugs to be laced with other drugs. Marijuana, cocaine, heroin and other drugs may contain meth, fentanyl and who knows what? See the DEA web site for many documented cases.
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.
We receive calls and messages regularly from meth users looking for an excuse for a positive meth test. Please do not be one of those people. If you use methamphetamine, get help.
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.
