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Understanding faint lines

What does a faint test line indicate?

If there is any hint of a colored line next to the T (as faint as it may be), it should be considered a negative result. See examples below.

What causes a faint T-line?

Simply answered, here are some possible reasons:

  • The test was not left in the urine sample long enough may cause a faint line. 
  • Chemical imbalances or dilution of the urine sample (ie. Too much water was drank before taking the test) may cause a faint line.
  • There is not enough THC in the system to trigger a positive result, however there still may be a small trace in the urine sample may cause a faint line.
  • Low detection level test may cause a faint T-line (ie. THC 20 ng/mL test, THC 15 ng/mL, COC 150 ng/mL).
  • The expiration date of the test has past, may cause a faint line.
  • Taking a medication that is chemically similar to the drug being screened may cause a faint line.

Can we explain further?

The most common cause for a faint T-line is that there is drug present in the sample, but not enough to trigger a positive result.

The image below shows the UTest THC 20 device with a control specimen that contains only 10 ng/mL of THC-COOH (THC metabolite). This is half the amount of drug needed to make the test turn positive, resulting in a negative result.

The THC15 and THC20 ütest+ devices represent the highest sensitivity for antibody-based THC drug screens, meaning a faint T-line would still indicate that the drug concentration is too low for a laboratory to call positive.

The best practice is to not over-interpret a faint T-line. A faint T-line with any hint of color should always be considered a negative result.

Other reasons:

  • Something in the urine other than the drug is causing a faint test line. Drug test scientists refer to this as “matrix interference.” It could be a urine sample that has a very low or high pH level, too much protein, high levels of sediment, a low specific gravity because of the donor over-hydrates or odd color due to medication. Given the inter-person variability and the biological nature of the antibodies used to make these tests, it is impossible to guarantee that every negative urine sample will yield dark test lines. As such, it is important to refer back to point #1 above and not over-interpret a faint line. A faint test line with any hint of color should always be considered a negative result.
  • The biological materials used to make the test are weaker than usual. Sometimes, the antibody or antigen used to make the drug tests will produce lighter lines on all specimens. While this is extremely rare, lighter test lines in completely negative specimens can result from a particular antibody lot. Excellent quality control management is conducted on UTest devices to ensure the best performance, so this phenomenon is extremely rare if almost nonexistent but the same adage applies: A faint test line with any hint of color should always be considered a negative result.
  • The test is expired. The biological materials used to make these drug screens have a well-defined shelf-life. The antibody activity will decrease or become non-effective after a fixed time, so the assigned expiration date is there to prevent customers from using a test after it has expired.


All orders processed by 10 am PT, Mon-Fri will be shipped out the same day unless otherwise notified.

Shipments are sent in discreet packaging.

PO Box addresses cannot be used for FedEx shipping options.

Domestic Shipments:

  • USPS 1st Class 1-5 days
    • $1.95 for orders less than $9
    • Free for orders more than $9
  • FedEx One Rate 2 Day Shipping (2 business days)
    • $4.75 for orders less than $19.95
    • Free for orders more than $19.95
  • FedEx Standard Overnight Shipping (1 business day)*
    • $19.95 for orders less than $79
    • Free for orders more than $79

* The only guaranteed shipment option is FedEx Standard Overnight. If an address provided does not allow for FedEx Standard Overnight, you will be contacted to choose a different shipping method. Please note, this option does not include Saturday delivery. For orders placed on a Thursday after 10 am PT, the delivery date will be the following Monday.

If an invalid address is entered by the customer and the shipment is unable to be delivered and is therefore returned to the Utest warehouse, a refund will be applied to the original form of payment minus the cost of the shipping.

Utest is not responsible for lost, stolen or delivered packages that were never received by the recipient.

To best assist with an issue regarding a USPS shipment, it is best to call the local post office (not the national hotline) or file a claim/request a lost mail search here.

To best assist with an issue regarding a FedEx shipment, the toll free customer service number is 800.463.3339 or to file a claim click here.

FedEx Canada:

  • FedEx Economy $16.95: 3-5 business days
  • FedEx Priority $22.95: 1-3 business days
    • Free for orders more than $79

*If FedEx Economy or Priority is not available with the given postal code provided after the order is placed, an email will be sent  with other available shipping options (shipping rates are subject to change and the price may be higher than the rates listed above).

ÜTest Drug Testing is not responsible for longer than average transit times going into Canada (ie. customs clearance delay) or any duties/taxes that may be collected upon arrival. If a different shipment method is preferred, contact customerservice@utestdrugtesting.com.

All Other International Shipments:

Contact customerservice@utestdrugtesting.com for rates and transit times.

Return Policy

We want our customers to be satisfied with their purchase.Returns may be accepted for the following reasons:

  • The wrong product was shipped
  • The product came in expired, proof of packaging with the expiration date; lot # must be provided
  • The results came up as “invalid” (no lines appeared next to the control or test lines)

Return requests must be made within 7 days of delivery by contacting customer service: customerservice@utestdrugtesting.com or 877.660.TEST (8378).

Tests that result in no line

What does a test line with no color (blanch) indicate?

If your test result looks like the image below, this generally indicates a positive result since there is no colored line present in the Test (T) region.

If this does happen please contact ütest+.

blanch results

Questions about the "C" line

The “C” line is darker than the “T” line. Is this normal?

Yes. The shade of the lines may very from test

The “C” line showed up at the same time as the “T” line. Did the test work properly?

Yes. As long as the “C” line is present, the test worked properly.

General Testing Questions

Should I take my drug test first thing in the morning?

The first urine sample of the day is always the most concentrated, but is not necessary to get accurate results.

Why do I have to take a urine test over saliva or blood?

It is cost effective, it can test for almost any drug, and has the flexibility of different cut off levels.

Does Ütest offer lab confirmation?

No, not at this time. Our tests are considered “pre-screening” devices, for further confirmation we recommend going into a lab.

What is the shelf life of the test I ordered?

All of our tests have an average shelf life of 12-18 months with exception of tests that are on sale.

There is no control line, what should I do?

In most cases, the test was not submerged into the urine sample long enough. Re-submerge the test into the urine sample and wait at least 10 seconds for the Control “C” line to appear. If it does not appear once again, the test is invalid. Contact our customer service for further help.

Why should I use an at home drug test?

Taking an at home drug test can help anyone before having to take a mandatory test to determine whether they will test negative or positive. Read our reasons for taking a drug test here.


Understanding Positive Results

Are your drug testing kits accurate?

Yes. We have an accuracy rate of 99%.

Does Ütest offer lab confirmation?

No, not at this time. Our tests are considered “pre-screening” devices, for further confirmation we recommend going into a lab.

I’ve been sober from THC for 30 days, how can I still be positive?

The timeframe of 30 days is just an average. THC drug can stay in the system for as little as 2 days and as long as 90+ days. This is due in part to THC being a fat soluble drug. It depends on how the body metabolizes the drug, how frequent the drug was used and how much was consumed. Click here, for more information.

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