How Long Methamphetamine Stays in Your System

Determining exactly how long meth is detectable in the body depends on many variables, many having to do with a person's unique physical characteristics. Furthermore, the type of test used matters. Methamphetamine—also known as Desoxyn, meth, crank, crystal, glass, ice, and speed—can be detected for a shorter period of time with some tests, but can be visible for up to three months in other tests.

Methamphetamine is metabolized by a liver enzyme and is excreted by the kidneys in urine. It is metabolized to amphetamine, p-OH-amphetamine, and norephedrine.

When taken orally, concentrations of methamphetamine peak in the bloodstream between 2.6 and 3.6 hours, and the amphetamine metabolite peaks at 12 hours. If meth is taken intravenously, the elimination half-life is a little longer—about 12.2 hours.

Various testing methods have different estimated ranges of times, or detection windows, during which meth can be picked up after a user has taken the drug.

The timetable for detecting meth in the human body is also dependent upon each individual's metabolism, body mass, age, hydration level, physical activity, health conditions, and other factors.

The effects of methamphetamine begin rapidly after intravenous use or when it is smoked. The main ones last from four to eight hours, with residual effects lasting up to 12 hours. Therefore, amphetamine is detectable in drug tests long after the user feels back to normal.

The effects of methamphetamine are also much different at prescribed therapeutic doses than those dosages usually used by meth abusers. Doses of 10 to 30 milligrams can improve reaction time, relieve fatigue, improve cognitive function testing, increase subjective feelings of alertness, increase time estimation, and increase euphoria.

However, larger dosages of meth can cause agitation, inattention, restlessness, inability to focus attention on divided attention tasks, motor excitation, increased reaction time, time distortion, depressed reflexes, poor balance and coordination, and inability to follow directions.

According to the National Highway Traffic Safety Administration, drivers who are under the influence of methamphetamine display a wide variety of behaviors including, "speeding, lane travel, erratic driving, accidents, nervousness, rapid and non-stop speech, unintelligible speech, disorientation, agitation, staggering and awkward movements, irrational or violent behavior, and unconsciousness."

In the 101 cases reviewed by NHTSA in which meth was the only drug detected, impairment was attributed to "distraction, disorientation, motor excitation, hyperactive reflexes, general cognitive impairment, or withdrawal, fatigue, and hypersomnolence."

Drugged Driving Laws

Many states have passed zero tolerance laws for driving while under the influence of methamphetamine. In those states, if a blood test shows any amount of meth at all, you can be charged with driving under the influence.

Because methamphetamine remains in the system long after the effects of the drug wear off, you might feel like you are OK to drive, but can still run the risk of being charged with drugged driving if any meth shows up in a blood or urine test.

Some meth users think that doing methamphetamine can reverse some of the impairment effects of alcohol. That's because meth may restore alcohol-induced impairment in simple repetitive tasks of short duration. However, NHTSA research has uncovered no restoration of alcohol-induced deficits of balance and steadiness.

The combination can also increase the risk of alcohol poisoning since users do not realize how much they’ve had to drink. In addition, heart rate is raised more than using meth alone, increasing the risk of future heart disease with long-term use.

Aside from the importance of being aware of how long meth remains in your body for the above safety reasons, know that if you take more of the drug while some is still in your system, you increase the risk of becoming dependent on this already highly addictive substance.

Meth carries with it a host of short- and long-term consequences and, if you use, quitting is advised. Seek the help of a medical professional who can help guide you through the treatment and withdrawal process—and beyond. If you don't have one, connect with a local social services agency or call the Center for Substance Abuse Treatment (CSAT) at 800-662-HELP.