Evaporation Line On A Pregnancy Test: Positive or Negative?

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Evaporation line


There’s a great deal of confusion when determining the difference between a positive pregnancy test and an evaporation line. For instance, you may have thrown out your negative pregnancy test, only to fish it out later and be shocked by a second line on the test strip. The majority of times, in this case, it won’t be a true positive pregnancy test. Instead, it’s a harsh feature of pregnancy tests, known as an evaporation line.


Understanding Pregnancy Tests

You have the option of three (typical) different types of at-home pregnancy tests: mid-stream, dropper, and dip tests.

Mid-stream tests: The pregnancy test strip is held in your urine stream for several seconds. It takes a few minutes for an accurate result to appear.

Dropper tests: A dropper is used to extract fresh urine from a cup, that is then dumped inside testing well.

Dip Tests: For a dip test you would urinate in a cup, then dip the test strip into the test cup.

The most important step to use any pregnancy test is carefully reading the instructions. Because Instructions vary between tests, in some cases, pregnancy tests with similar packages have slightly different instructions for each test.

After the pregnancy test’s waiting period passes, you would look at the results window to examine whether the test result is positive or negative. A positive pregnancy test is usually shown as two lines, a plus sign, or a message like ‘yes’ or ‘pregnant’.

Pregnancy tests that show two lines will already have two indented lines where the ink pools: The first line is the control line, and the other one is for potentially positive pregnancy test results. While the ink travels into the result window, it can pool into one or two indents depending on the pregnancy result.


Distinguishing Evaporation (Evap) lines from a Positive Pregnancy Test

Evaporation (Evap) lines are faint lines that show up after a negative pregnancy test dries up, tricking a user into reading a false positive. This simple feature of pregnancy can be cruelly misleading. Pregnancy tests have a reaction time, which is usually around three to five minutes after they’re taken and when the test is still damp. When their time frame passes, the urine used in the pregnancy test begins to dry up.

When the pregnancy test ink makes its way across the test screen, your result is shown. While the ink makes its way across the screen, a small amount of ink can get stuck in the indent line. When the pregnancy test begins to dry, your urine evaporates. The ink that gets stuck gets pulled to the top and darkens. Thus, it tricks users into getting a false positive. That’s why the most important instruction for getting a true pregnancy result is to examine your pregnancy test during the allotted time. You can be sure you read the results in an accurate time-frame based on the package’s specific instructions.


Understanding HCG Levels

At-home pregnancy tests are widely used to detect pregnancy, but there are still risks of false negatives and false positives. A false negative can happen if you take a pregnancy test too early. Errors usually happen before a missed period or when your body’s Human Chorionic Gonadotropin (hCG) levels are too low.

False positives are not as common, yet they can still occur with a chemical pregnancy. This type of pregnancy occurs when a fertilized egg is implanted into the uterus, and then miscarry soon after.


Distinguish a Faint Positive Pregnancy Test from an Evap Line

Now you’ve learned how to spot a pregnancy test that’s a false positive. However, sometimes you may see a faint line during the exact time frame allotted by your pregnancy test.

  • Don’t take your pregnancy test too early. It’s recommended to take your pregnancy test 12-14 days after you ovulate. Repeat your test two days after, independent of the result you get. This is because hCG levels are still low. When hCG levels rise, a true positive pregnancy test will become darker.

    Finding out when you’re ovulating is difficult, and visiting a doctor on a consistent basis isn’t ideal for many. However, through a clinical trial conducted with many patients, the Mira Fertility tracker was found to be equivalent in performance to leading laboratory-grade readers, in terms of measuring your actual fertility hormone concentration at home.


  • Take a sensitive pregnancy test. hCG thresholds to display a positive pregnancy result vary depending on your pregnancy test kit. A downside of testing early is that you’re more likely to test for a chemical pregnancy. This type of early miscarriage is common, and many women have chemical pregnancies without even realizing it.


  • Refrain from over-hydrating yourself. Drinking large amounts of water and urinating frequently could possibly dilute your urine too much for an accurate reading. It’s recommended for women to limit fluid intake for at least a couple of hours to ensure an undiluted reading. Also, your first urine stream in the morning is much more concentrated than urine samples from a random time in the day.

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What if there is a Line with No Color

For a pregnancy dip test, a positive result will have two perpendicular (T-shaped) lines that are the same color. When there is a faint second line or one with no color at all, it’s highly likely that its an indent line.

Do you recall the previous discussion about indent lines and how pregnancy tests work? Indent lines may sometimes become barely visible, in a similar way that ink can mistakenly pool into the indent line. When the second line on your pregnancy test is gray/colorless, then it probably is an indent and not positive test.



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