How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Lani, BSN, RN Your Own Question
Lani, BSN, RN
Lani, BSN, RN, Nurse
Category: Health
Satisfied Customers: 4741
Experience:  A Registered Nurse for 19 years.
Type Your Health Question Here...
Lani, BSN, RN is online now
A new question is answered every 9 seconds

Can an infrequent user of marijuana pass a hair drug test.

Resolved Question:

Can an infrequent user of marijuana pass a hair drug test. Our son failed 2 urine tests, but passed the hair test. How is this and what test should we go by. We think he has smoked marijuana maybe twice in the last 6 weeks.
Submitted: 9 years ago.
Category: Health
Expert:  Lani, BSN, RN replied 9 years ago.

Hello myswiftly,

Based on some studies, it proved that hair drug testing significantly detects drug usage more than the urine test. It only takes approximately 4-5 days from the time of drug use for the affected hair to grow above the scalp, thus hair test done after few days of usage will usually show up positive for the drug use. Hair test is usually very sensitive and can be even used to identify the deter mine low (occasional), medium (weekend, daily) or high (constant) usage. However, for the detection of marijuana it is said to be less sensitive than the other drugs in identifying low level drug users

In the case of your son, it is quite strange to have been tested positive in urine and did not show up in the hair test. There could be possibly a significantly low levels of marijuana metabolites present in the hair not enough to yield positive result. A Gas Chromatography Mass Spectrometry (GC/MS) should be done to verify his marijuana usage.

Lani, BSN, RN and 4 other Health Specialists are ready to help you