Blood Drug Testing

Home drug test kit had a really light line for negative?

I took a home drug test for THC last night and it came back negative but the negative line was really,really faint but it was still there. Why was the line so faint?

Public Comments

1. There could be a few reasons why this may occur. Let’s talk about how a drug test works and what are the differences between an instant home drug test and a lab based drug test. First of all urine drug tests do not test for the drug specifically, but rather they test for the metabolite of the drug. Meaning it tests for what the drug turned into after it was consumed by an individual. An instant drug test or screen for THC (Marijuana) tests at a level of 50 ng/ml. Meaning anything over 50 ng/ml will come back positive and anything below that will be negative. A lab based test will also screen at 50 ng/ml, but and here’s the kicker if the test shows questionable or if it’s positive the lab will do a confirmation test called GC/SM and this test is 100% accurate. It’s so accurate that it will test at a level of 15 ng/ml. Now back to your home drug test kit. A faint line is counted as a line and it's a negative result. Now with that being said, if a line is so faint that one can barley see it then it’s questionable. When a line is so faint that you can barley see it one must say that you’re hovering at the cut off level and if you took a lab based test you would probably fail. You need to take another test to see if it’s still really faint. Also be aware that urine samples taken during different times off the day will have different concentrations of the drug metabolite. i.e a morning urine sample would have a much higher concentration the a sample taken in then afternoon. Also check out this website they have a resource page and a blog that discusses this in more detail.