Pregnancy Test Faint Lines and Evaporation Lines

The Two Big Pregnancy Test Questions:
1) How Early Can I Test for Pregnancy?
2) What Does a Faint Line Mean on a Pregnancy Test?

> Back to Pregnancy Testing [1]

How Early Can I Test for Pregnancy?

One question women frequently ask when trying to conceive is: How long do I have to wait before I can take a pregnancy test [2]? Though hCG is produced at different rates in different women, there are general timelines for deciding when to test. However, when testing on the early side, do not rely on one test for conclusive results - especially a negative result: the hCG threshold for displaying a positive result on a home pregnancy test may not yet have been reached.

Early Detection Pregnancy Tests

When a woman becomes pregnant, the amount of hCG in her system should be around 25 mIU at 10 dpo (days past ovulation), 50 mIU at 12 dpo, 100 mIU at around two weeks dpo (these are averages that may deviate among different women). Test sensitivity equates with early-detection - and the lower the number, the sooner a test can detect pregnancy. At 20 MIU test sensitivity, you can begin testing at 7-10 days post ovulation, though the earlier you begin testing, the higher chance you have of getting a false negative. Early-Pregnancy-Tests.com [3] carries early-detection pregnancy tests [2] capable of detecting just 20 miu/ml hcg.

Here, implantation of the fertilized egg needs to take place before hCG is produced by the developing placenta, and that generally occurs at 6-10 dpo. If you decide to test early, make sure you perform a few follow-up tests every other day using first morning urine. Your hCG levels should rise exponentially, doubling every 2 days - which means that the follow up tests should eventually detect pregnancy if you are, in fact, pregnant.

For earliest detection of pregnancy, use first morning urine, as this urine sample contains the most concentrated amount of hCG. If using first morning urine is not feasible, avoiding urination for several hours before using a pregnancy test [2].

A faint color band in the test area of a pregnancy test indicates, in most circumstances, a positive result for pregnancy.

However, a faint line appearing after the designated reaction time of the test may be an "evaporation line".

What Does a Faint Line Mean on a Pregnancy Test?

On a pregnancy test [2], a faint test line - or color band - is usually indicative of a positive result, as long as it's read within the time frame - or reaction time of the test (usually at 5-10 minutes). If you perform the pregnancy test properly and read results within the recommended time frame, then a faint or weak color band in the test area is very likely a positive pregnancy test.

Evaporation Lines

Evaporation lines, however, can confound results if tests are not interpreted within the clinically recommended time frame. An evaporation line develops when the urine on the test area begins to dry, leaving a faint, usually colorless line. Evaporation lines appear to show up (or not show up) as a result of the composition of the particular urine specimen - and they may appear on any test regardless of brand.

Explanations for Faint Positives

Testing Too Early: If you test too soon, hCG may not be at a sufficient level for test detection. See the section above on determining when to take a pregnancy test.
Low Test Sensitivity: Different tests detect hCG at different levels, from 20MIU to 100MIU or more. 20 MIU tests [2] will display a faint line when when hCG levels are at 20 MIU, while less sensitive tests will display a negative result. At 50 MIU levels, a 20 MIU test will show a stronger color band while a 50 MIU test will show a very faint band.
Dilution of Urine Specimen: Urine specimens may be diluted due to frequent urination or consumption of liquids. First morning urine is recommended for pregnancy testing as it contains the most concentrated presence of hCG.
Chemical pregnancy: Sometimes an early pregnancy is detected - followed by negative test results. A chemical pregnancy means implantation takes place (hCG is produced for a short time) followed by a miscarriage (generally, before any other pregnancy symptoms are detected).
Evaporation Lines: Always read your test results within the test reaction time (usually 5 minutes) as evaporation lines can develop as the urine dries on the test area. Evaporation lines appear to show up (or not show up) as a result of the composition of the particular urine specimen - and they may appear on any test regardless of brand.

Remember, a pregnancy test does not function like "light switch" - and just turn on: different hCG levels will produce different gradients of color bands (from very light, faint lines early in pregnancy to dark, rich color lines later on as hCG develops).