What Is a Hair Follicle Drug Test?

Q: What Is a Hair Follicle Drug Test?

Hair follicle testing detects drug use for up to 90 days. Cannot detect use from the last 5-7 days. Each 0.5 inch of hair = 30 days of history.

Hair testing analyzes drug metabolites deposited in the hair shaft as it grows.

Detection Window

Up to 90 days
Cannot detect last 5–7 days
0.5 inch = 30 days of history

Detects

THC, cocaine, amphetamines, opiates, PCP

Advantages

Longer window than urine
Harder to adulterate
Non-invasive

Disadvantages

Cannot detect recent use
More expensive
Hair treatments may affect results

Source: SAMHSA, NIDA, Mayo Clinic.

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