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What is a Pregnancy Test Evaporation Line?

Table of Contents

What is a Pregnancy Test Evaporation Line

Table of Contents

Introduction: Pregnancy Test Evaporation Line

Heard about the dreadful confusion of an evaporation line and a positive pregnancy test evaporation line ?  You understand what we’re talking about if you’ve ever thrown away a negative pregnancy test only to dig it out later and be stunned by the second line. Most of the time, it’s an evap line, simply a scare rather than a true positive.

How can you be certain that the second line is a real positive? Let’s first study how a  pregnancy test  works to learn, why evap lines develop and how to read the pregnancy test evaporation line results right.

So, How Do Pregnancy Tests Work?

A fertilized egg has to implant itself in the uterine lining to start a pregnancy. Only an ectopic pregnancy is an exception where the embryo attaches outside of the womb’s inner lining.

Human chorionic gonadotropin (hCG) is a hormone that the body begins to generate during implantation. During the first trimester, the body’s hCG levels rapidly rise in the first trimester by at least 49% per 24 hours. hCG levels decrease at the end of the first trimester. Home pregnancy tests (HPT) detect these levels and give you a result, positive or negative.

HPTs come in three different types: mid-stream tests, dropper tests, and dip tests.

  • Mid-stream tests: These are placed in the urine stream for a short amount of time before being removed. Wait for a few minutes to get the results.
  • Dip tests: This involves peeing into a cup, followed by dipping the test—typically a strip—into the cup.
  • Dropper tests: In these tests, urine is injected into the testing tube using a dropper filled with freshly collected pee from a cup.

Instructions for different tests differ, and sometimes a single set of tests has many unique types with different instructions for each. To avoid wasting your pee, be sure to read them completely. When the waiting period is over, you may check the results pane to see if the test was successful or unsuccessful. Positive results are shown by a plus sign, two lines, or a direct statement like “yes” or “pregnant.”

The tests that provide results on two lines include two “indent” lines that are hidden where the ink pools—one for the control line and one for a positive result. The ink gathers in one or both of these indents as it moves across the result window.

How Much hCG Can Be Detected in a Positive Pregnancy Test?

The average concentration of hCG in urine 9 days after ovulation, or about 5 days before a missed period, is 0.93 milli-international units per milliliter (mIU/ml), according to 2014 research.  When hCG levels reach 25 mIU/ml or above, which happens after ovulation or on around day 11, most early-result pregnancy tests can confirm a pregnancy.

The average hCG level at day 14 is 137 mIU/ml. However, for some, they can be as low as 45 mIU/ml.

False positives are less common than false negatives. For a high chance of getting a positive result, make sure you give some time for the hCG levels in your body to rise. Always take a second test to confirm.

What is an Evap Line on Pregnancy Test?

A faint streak, known as a pregnancy test evaporation line, emerges where the positive lines on a pregnancy test ought to be.  Pregnancy Test Evaporation lines are not thin lines; they are colorless streaks that frequently surface if a person waits past the recommended time before reading the test result. An Pregnancy test evaporation line may also appear if the test becomes moist.

Pregnancy is not indicated by an evaporation line. An evaporation line indicates a negative result or that the test was administered too early in the pregnancy for a positive result. To know more about faint lines during early pregnancy tests, click here.

How is an Evap Line Different From a Positive Pregnancy Test?

After a negative test has dried, a thin line known as an evap line (evaporation line) will show up. The tests will still be damp when they are read for 3 to 5 minutes after being taken. The pee in the test dries after this amount of time has passed.

The result is shown as the ink moves over the screen. Sometimes, a small amount of ink will unintentionally get stuck in the indent line as it advances across the screen. This captured ink is drawn to the surface and darkens as the test dries and the urine evaporates.

Therefore, the key rule is to never read a pregnancy test after the specified period. Only the time covered by the instructions guarantees the accuracy of the results.

A Final Word on Evaporation Line on Pregnancy Tests

When a woman first wakes up, their urine usually has the greatest hCG levels. The likelihood of receiving a quick positive answer might be increased by taking the test first thing in the morning. So how can you be certain that a pregnancy test result is accurate?

  • Avoid testing too soon. Your hCG levels will be lowest if you test early. Test once again in a day or two to see if you have a real squinter. A true positive test will get darker as hCG levels rise.
  • Try a more accurate test. Different hCG thresholds must be met by various test kinds and brands for a positive result to be displayed.
  • Remember that one drawback of early testing is that you are more likely to discover a chemical pregnancy. These very early miscarriages are rather typical and they usually do not indicate any sort of underlying fertility issue.
  • Avoid overhydration. Your urine may be too diluted for an accurate result if you have been consuming a lot of fluids and/or urinating often. So refrain from drinking anything for two to three hours.

Pregnancy tests can be nerve-wracking but they needn’t be if you follow the correct guidelines of whichever brand you are using. Test at least twice before confirming and going to a doctor. Happy pregnancy (or not)!

FAQs: Pregnancy Test Evaporation Line?

1. How do you tell if it's an evap line or positive?

It might be stressful to wait for pregnancy test results. The test is probably positive if the result displays any colored line, no matter how faint. If the outcomes reveal a thin, colorless line, this could be an evaporation line.

2. What is an evap line?

Every pregnancy test has a chance of producing evaporation lines. As the urine dries, a line known as an evaporation line appears in the pregnancy test results window. It can leave a thin, invisible line. If you are unfamiliar with evaporation lines, you can mistakenly believe that you are pregnant if you see this line.

3. How soon does an evap line show up?

After 10 minutes, a mark known as an evaporation line will form. Test again the next day for the best results in determining whether you are pregnant. True positives will show up in two to ten minutes, whereas urine will take some time to dry and produce streaks.

4. Is an evap line thick or thin?

Additionally, an evaporation line is typically narrower than a control line. The vertical evaporation line is significantly thinner and has an uneven thickness whereas the horizontal line has one thickness.

5. Does the evaporation line get darker?

This captured ink is drawn to the surface and darkens as the test dries and the pee evaporates. The most important guideline is therefore to never read a pregnancy test after the specified period to receive a true positive result. Only the time covered by the instructions guarantees the accuracy of the results.


On behalf of the editorial team at Parenthoodbliss, we follow strict reporting guidelines and only use credible sources, along with peer-reviewed studies, academic research institutions, and highly respected health organizations. To learn about how we maintain content accurate and up-to-date by reading our medical review and editorial policy.

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