How does methamphetamine get out of the body? The average half-life of methamphetamine is about 12 hours. This means it takes about 12 hours for half the amount of meth snorted, swallowed, smoked, or injected to be processed and excreted through the body's natural exits, such as through sweating, urinating, or moving the bowels.2, 9
The main way that meth exits the body is through renal excretion, also known as urination. The pH of the user's urine will determine how quickly the meth exits the body. The pH is a measure of the acidity or alkalinity of the urine, or any solution, for that matter, where two or more substances are mixed together. The more acidic the urine, the faster meth will exit the body. Acidic urine can speed up the exit process to seven hours instead of 12. Basic (alkaline) urine can slow down meth's excretion by increasing its half-life to 30 hours.2, 9
Some illegal meth users drink vinegar or cranberry juice, both of which are very acidic, to try to cleanse themselves of methamphetamines before a drug test. However, even low doses of meth produce a positive urine test for about 24 hours after taking the drug. High-dose users can test positive for meth for two to four days after their last use.2, 9
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