How Long Does Meth Stay in Your System?

person holding  a bag of crystal meth

Methamphetamine, commonly referred to as meth, can be prescribed for narcolepsy and attention-deficit hyperactivity disorder (ADHD). Even though meth is medically viable, the drug is highly addictive and harmful. Because of its poor reputation, most doctors would not prescribe methamphetamine for narcolepsy or ADHD — if someone is taking meth they’re likely doing so illegally.

People use meth because it gives them feel euphoric. The drug increases their energy levels while lowering appetite, which can lead to weight loss. Tolerance to meth builds quickly, so people will have to increase their dose to keep getting the same euphoric effects. When larger amounts of meth are consumed, the metabolites of the drug remain in a person’s body for longer periods.

So, how long does meth stay in your system? The answer depends on many factors. A single dose will leave the body in just two days, but taking meth more frequently can affect how long the drug remains in your system.

The purity of the meth also makes a difference. Crystal meth, a more purified and potent version of methamphetamine, triggers a longer-lasting high and stays in a person’s system longer than other forms of meth.

Duration of Effects of Meth

Meth causes peak effects within a few hours but takes a few days to leave the body completely.

Once meth causes the desired effects (euphoria, energy or low appetite) the drug stays in the bloodstream even after the desired effects wear off.

The effects of meth last about eight hours, regardless of how a person chooses to use the drug.

Methamphetamine Half-Life

A half-life is the amount of time it takes for the body to clear half of a drug out of the system. Meth’s half-life is 10 hours and is the same regardless of how it is taken.
For example, if a person takes 30 mg of methamphetamine at 8:00 AM, by 6:00 PM (10 hours later), half of the original amount (now 15 mg) will remain in the bloodstream. By 4:00 AM the next morning, 7.5 mg will remain in the bloodstream.

Meth Screening Detection Times

Meth detection times are quite long. Most meth drug screens can capture usage up to a week following meth’s last use. Meth drug tests can be conducted using a person’s blood, urine, saliva or hair. Each element has its own detection window.

Urine

Urine drug tests are the most common type of drug test because it is inexpensive. Meth is detectable in urine for 4-7 days after the last dose. Detection time may be higher for people who abused meth for months or years.

Blood

Meth shows up in the blood within hours after first use and can remain in the bloodstream for about 2 days. Meth blood tests are mostly commonly used by the police and in medical settings.

Saliva

Saliva testing involves collecting a sample by swabbing the mouth or tongue with an absorbent material. Meth use can be detected in saliva for 3 days after the latest use.

Hair

A meth hair test can detect meth use for up to 90 days in most tests, but more expensive tests can accurately detect meth use for up to 180 days.

When meth is in the bloodstream, it reaches the scalp and deposits into hair follicles. The hair then grows with traces of meth in it. Hair grows about 0.5 centimeters per month. Most tests take 1.5 cm of hair for testing.

Meth stays in the follicles only briefly until that portion of the follicle grows into the hair. However, meth stays in the hair until the hair is cut or falls out.

Factors Affecting How Long Meth Stays in Your System

There are several factors that affect how long meth is detectable in a person’s system. Common detection factors include:

  • Amount used: Using even a small amount once is enough to create a positive result on any drug test for at least two days. Using larger amounts will extend the detection time.
  • Age: Older people may break down meth slower than younger people do and therefore prolong detection time, but no studies have proven this as a fact.
  • Overall health: Health issues like heart, liver and kidney problems will increase the length of time meth remains in the body.

False Positives for Meth

False positives for meth are relatively common because the drug’s molecular structure is simple. When a drug test “looks” for meth, it may accidentally find a molecule with a similar shape, which can cause a false positive.

  • Meth false positive causes due to a medication can include:
  • Allergy medications (chlorpheniramine, brompheniramine, pheniramine)
  • Antidepressants (bupropion, trazodone, selegiline, fluoxetine, tricyclic antidepressants)
  • Decongestants (phenylephrine, ephedrine)
  • DMAA, an energy supplement
  • Phentermine, an appetite suppressor

When a drug test comes back positive, the person tested will be asked about any other medications they are taking to rule out a false positive.

The sample is then sent to another lab for a test called gas chromatography-mass spectrometry. This type of analysis can confirm the sample with almost 100% accuracy, so a false positive drug screen will then be verified.

How Meth is Broken Down in the Body

Meth is mostly broken down in the liver. The liver creates proteins that break down meth by attaching other molecules to it or by changing its shape.

The products of metabolism (metabolites) are removed from the body through the intestines (stool) or the kidneys (urine). A small amount evaporates through the skin as sweat.

If you or a loved one struggle with meth addiction, The Recovery Village Ridgefield can help. Call today to speak with a representative who can help you find the treatment best suited for your needs.

Cone, Edward; Huestis, Marilyn. “Interpretation of Oral Fluid Tests for Drugs of Abuse.” Annals of the New York Academy of Sciences, March 1, 2007. Accessed July 19, 2019.

Cruickshank, Christopher; Dyer, Kyle. “A Review of the Clinical Pharmacology of Methamphetamine.” Addiction, 2009. Accessed July 19, 2019.

Moeller, Karen; et al. “Urine Drug Screening: Practical Guide for Clinicians.” Mayo Clinic Proceedings, January 2008. Accessed July 19, 2019.

Psychemedics. “Hair Drug Testing Facts and FAQs.” Psychemedics, 2015. Accessed July 19, 2019.

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