The drug test strip on the right-hand side has a very faint T line
We recently received this question below via e-mail about interpreting faint lines on urine drug test strips.
Hi was wondering if you could help. I recently purchased some single-use cocaine tests strips. One test I did came out with the positive line straight away, then a very faint negative line appeared. When I read the info on the leaflet it said that faint lines should be read as negative so I’m now confused. I was sure it was positive as it was so clear and the other line was so faint. Can you help, please?
How to interpret a faint line
In this question, it is not specified at what time the test was read. It is possible for the test to appear to be a positive result initially ( i.e. no line which then turns negative within the test time (T line visible ) If the test line appears within the specified time in the instructions it is a negative result even if it is very faint. If you are unsure you can always send us a photo of the result and we will be able to advise further.
Read UK Drug Testing FAQ section for advice on reading faint lines on drug tests
Drug test kit with both C & T lines visible on each test membrane. You will note that some lines are fainter than others.
We received this question earlier by e-mail and it is something that can cause confusion.
The C line or control line on a drug test kit is usually very strong and dark however the T line (test line ) may vary considerably in colour and darkness from test to test and also on different drug test membranes, within the same drug testing kit. This is quite common and is of no significance when interpreting the result of the test.
As long as the T line is clearly visible within the specified time then the result is a negative result i.e. no drug detected. The T line does not need to be as dark as the control line and in fact often is not. On the multi panel urine drug test kit above, you can see that the intensity of the T line varies on the different strips although the control line remains fairly consistent.
We are also often asked can any conclusion be drawn if the T line is faint and does this mean there might be low levels of drugs present. The answer to this is no. The faintness of the T line is not of any significance and is still a negative i.e. clear or pass result.