Drug Testing FAQ

Q: How do drugs get into hair?

A: As drugs circulate in the blood stream, they enter and nourish hair follicle cells. As cells grow, they trap the drug molecules within the hair cells and are eventually "sealed" in the keratinized hair shaft. Thus, the amount and time the drug(s) are in the blood stream is proportional to the amount of drug detected in the hair. THC stays in your blood for 2-3 days.

Q: How soon after use can a drug be detected in hair?

A: It takes approximately 5-10 days from the time of drug use for the affected hair to grow above the scalp.

Q: When THC metabolites are filtered into the hair do they create a ring around the hair follicle? Or does THC migrate along the shaft like cocaine does? The essential question being will cutting my hair short enough work?

A: Hair testing requires a sample of hair about the diameter of a pencil and 1-1/2 inches long. They can not be done with a single hair. So approximately 50 strands of hair from the scalp are sent to a testing lab where it is liquefied. The hair sample is dissolved in a series of solvents which extract the drug metabolites and then are analyzed via GC-MS. It can take several hours to days just to extract metabolites. The liquid is run through the most sensitive GC-MS machines available, and can detect as little as 1 ng/mL.

Q: How much hair do they need?

A: A standard screen with GC-MS confirmation requires 20 milligrams of hair or approximately 60 strands.

Q: Can tests be run on people with little or no hair?

A: Yes, hair can be collected from several locations on the head and combined to obtain the required amount of hair. In addition, body hair can be used as an alternative to head hair.

Q: Does body hair give the same type of results as head hair?

A: Yes, body hair can be used to test for the five standard drugs. Body hair growth rates are considerably more variable and slower than head hair. Most body hair is genetically controlled and replaced within one year. Therefore, it is difficult to accurately represent the time period of a standard screen with body hair.

Q: How does the testing lab establish its cut-off levels?

A: Cut-off levels are established by the minimum detection levels for GC-MS confirmation, which are given by NIDA.

Q: What is the cut off level for cannabis in a hair test?

A: Carboxy-THC 1 pg/mg (.001 ng/mL).

Q: How long does it take a lab to test a sample?

A: 4-5 business days.

Hair Growth Information

Per Day: 0.44 mm, 0.0173228 inches
10 Days: 4.4 mm, 0.173228 inches
20 Days: 8.8 mm, 0.346457 Inches
30 Days: 13.2 mm, 0.519685 Inches
40 Days: 17.6 mm, 0.692913 Inches
50 Days: 22.0 mm, 0.866142 Inches
60 Days: 26.4 mm, 1.03937 Inches

How Quickly Does Hair Grow?

On the eyebrows, the growing phase is only about 10 weeks, so eyebrow hairs never grow very long. Pubic and armpit hair growth rates are roughly similar, while leg hairs grow more slowly and are shorter. So these types of hairs are replaced about every 10 weeks. According to Health News, "Armpit hair grows at about .3mm per day." and that "healthy scalp hair grows an average of half an inch or one centimeter per month."

Comb Cutting Attachments

#1: 3 mm, 0.125 inches
#2: 6 mm, 0.250 inches
#3: 9 mm, 0.375 inches
#4: 12 mm, 0.500 inches
#5: 16 mm, 0.625 inches
#6: 20 mm, 0.750 inches
#7: 25 mm, 1.000 inches

Shampoo Information

Propylene glycol is the primary chemical in detox shampoos that removes carboxy-THC from hair. There was some misinformation in the original version of this FAQ. EDTA will not help you pass a drug test. It removes metal ions from hair, and has little or no effect on lipophilic organic molecules like cannabinoids.


Aloe Rid by Nexxus. Since so many people swear by this stuff, I thought I would put the complete ingredient list down. Only one EDTA is present.

Aloe Rid Treatment by Nexxus. Used with Aloe Rid Treatment to eliminate "chlorine green" and other pool or spa chemicals. Combats swimmer's hair and chemical build-up.

Shampoo Note

For every story of someone using a "home remedy" or so-called detox product and passing, there's another story of someone else doing basically the same thing and failing. The truth is, it's all a big crap shoot for people who have been regular users. The only guaranteed way to pass a hair is abstinence and time. Quit for about 90 days prior to being tested, and get one reasonably short hair cut per month to get rid of all the evidence. I think the consensus seems to be that "detox miracle products" don't work. Most people use the MacCuj0 method or a variation because it is cheep and has given good results to many people. Although not working for everyone. Using Nexxus Aloe Rid or Paul Mitchell Shampoo Three is an everyday treatment that relatively inexpensive and seems to aid in cleansing your hair of toxins. You have to wash your hair anyway so why not use one of the two or both.

Other Drug Hair Test Information

Drug test cutoff levels for the GC-MS hair follicle test