Why Did a Second Line Appear Later on My Pregnancy Test?

Photo illustration of a positive pregnancy test

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Taking a pregnancy test can sometimes be confusing. You might be wondering how reliable your result is or you may be confused about how to read your test. Understanding how these tests work is key to interpreting what shows up after you pee on that stick.

When you take a home pregnancy test, you're looking at the testing window to see whether there are two lines or just one. The first line is the control line. If that's all you see, your result is negative. But two lines in the testing window mean that you are pregnant.

Home pregnancy tests measure a hormone called human chorionic gonadotropin (hCG) in your urine. Your body starts producing hCG after a fertilized egg implants itself in your uterus, about six to ten days after ovulation. And since you only produce hCG during pregnancy, even the faintest suggestion of a second line indicates that you have conceived.

To take the test, direct your urine stream over the test stick or collect your urine in a sterile container and dip the stick into it for about 20 seconds. Check the test again in about three minutes to see whether one or two lines appear.

These results are only valid for 10 minutes after your test though. If you get a negative result and you happen to glance back at the test later in the day, you may be surprised to see that a positive line has magically appeared. There are a few reasons why this can happen. However, in most cases, the originally reading of the test, "not pregnant," is typically the correct one.

Knowing You're Pregnant

You can say for sure that you are pregnant if you see a positive result within 3 to 10 minutes of taking the test. Remember that it doesn't matter how faint that line is, because your body only produces hCG pregnancy hormone while you are pregnant.

Sometimes you'll see a faint line if you test on the earlier side and the hCG is still building up in your system. A line that gets progressively fainter over days of testing may indicate that you are miscarrying, so reach out to your provider if this happens.

A positive pregnancy test can almost always be considered reliable. However, this many not be true if you are taking certain fertility drugs. Drugs used to trigger ovulation may contain hCG. Until these medications clear from your system, you could get a positive result when you are not pregnant.

What Happens If a Positive Lines Appears Later?

The instructions on most pregnancy tests will advise you to read the results within a certain window of time. This usually ranges between a couple of minutes up until 10 minutes later. If you see a positive result beyond this time frame, you may be left second-guessing the results.

However, always remember that a pregnancy test result is only accurate within 10 minutes. After the that, it's best to throw the test away to avoid confusion.

Evaporation Lines

If urine splashes onto the test window, it can dry, leaving streaks. If one of these streaks appears right around the spot that you are looking for your positive, it can look like a second line.

The easiest way to differentiate between a positive test result and evaporation line is to check your test within the allotted time. A true positive will appear within two to 10 minutes, while urine won't dry and form streaks until some time later.

What If My Positive Line Is Faint?

If you follow all of the instructions correctly, you may notice a thin, faint test line that appears within a few minutes.

There are several possible explanations for this line's faintness. You may have taken the test too early in your cycle. If you test earlier than 10 to 12 days past ovulation, the hCG hormone may not be high enough to produce more than a very faint line. The best time to test is after your period is late, or 2 weeks after you ovulated.

Your urine might also be diluted, skewing the test's results. You can dilute your urine sample if you are drinking too many liquids—this is why first-morning urine samples are recommended for pregnancy testing.

Some pregnancy tests have lower sensitivity levels, so they'll show fainter lines earlier on. Although it's not necessary, you can try retesting with a different type of test if you want to see a darker line. Look for "early results" indicated on the test label.

If your positive result is appearing lighter each day, this could mean that you are having an early miscarriage. Remember though that many factors can impact how light or dark your positive line is, such as using different test brands, drinking different amounts of fluids, or testing at different times of the day. Reach out to your healthcare provider if you have an concerns about your pregnancy.

False Negative Results

While it's nearly impossible to get a false positive pregnancy result, false negatives can definitely happen. Even if you're pregnant, your hCG levels may still be too low to be detectable in your urine. This is more common if you test before your period is due, but it can also happen right around the time of your missed period.

Many of the same factors that cause a faint line can also cause a false negative, such as diluted urine or lower sensitivity tests. If you still haven't gotten your period, wait a few days and test again. HCG builds rapidly in your system, so you may see a positive soon after seeing a false negative. Always use a sample from your first-morning urine (which is more likely to have higher concentrations of hCG.

Next Steps

If you get a positive pregnancy test, contact your healthcare provider or search for an OB/GYN in your area. They will likely ask you to come in some time around seven weeks past the first day of your last period. At this visit, you provider will do an ultrasound to confirm pregnancy.

If your test is negative, wait for your period to come. If you want to get pregnant, you can start trying again shortly thereafter.

If you take a pregnancy test and you're really not sure what it's telling you, you can always test again the next day. Sometimes this is the best way to get rid of any stress surrounding a confusing test result. Consider saving your urine in its container until you get your results, so you can reuse it for a new test.

A Word From Verywell

Bringing a new baby into the world is a big deal and will impact decisions you make in the near future. It's not surprising if conflicting or confusing pregnancy test results leave your feeling stressed or anxious. Remember this--you can generally count on a positive result to be accurate, but you can't be totally sure about a negative result until you get your period.

To avoid any confusion caused by evaporation lines, read your test after three minutes and throw a negative result away once 10 minutes have passed. If you do see any changes, only assume that your test was accurate during the 10 minute window.

If you get a positive test, contact your healthcare provider. They will have you come in for an ultrasound or blood test to confirm your pregnancy.

6 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  3. Järvelä, Ilkka Y., et al. “Improved Pregnancy Rate with Administration of HCG after Intrauterine Insemination: A Pilot Study.Reproductive Biology and Endocrinology, vol. 8, no. 1, Dec. 2010, p. 18. DOI.org (Crossref), https://doi.org/10.1186/1477-7827-8-18. doi: 10.1186/1477-7827-8-18.

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By Robin Elise Weiss, PhD, MPH
Robin Elise Weiss, PhD, MPH is a professor, author, childbirth and postpartum educator, certified doula, and lactation counselor.