Are You Pregnant? Pregnancy Tests When the Pregnancy Test Positive Line Shows up Later By Robin Elise Weiss, PhD, MPH Robin Elise Weiss, PhD, MPH LinkedIn Twitter Robin Elise Weiss, PhD, MPH is a professor, author, childbirth and postpartum educator, certified doula, and lactation counselor. Learn about our editorial process Updated on October 17, 2021 Medically reviewed Verywell Family articles are reviewed by board-certified physicians and family healthcare professionals. Medical Reviewers confirm the content is thorough and accurate, reflecting the latest evidence-based research. Content is reviewed before publication and upon substantial updates. Learn more. by Rachel Gurevich, RN Medically reviewed by Rachel Gurevich, RN Facebook LinkedIn Twitter Rachel Gurevich is a fertility advocate, author, and recipient of The Hope Award for Achievement, from Resolve: The National Infertility Association. She is a professional member of the Association of Health Care Journalists and has been writing about women’s health since 2001. Rachel uses her own experiences with infertility to write compassionate, practical, and supportive articles. Learn about our Medical Review Board Print Verywell / Michela Buttignol / Getty Images After getting a negative result on a home pregnancy test, it's fair to conclude that you're not pregnant. However, if 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. Evaporation Lines 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, the false-positive reading, in this case, is due to something called an evaporation line. Evaporation lines are not indicative of a true positive result. Evaporation lines happen when the urine that was on the test area starts to dry. The chemical composition of the urine sample changes due to evaporation. As a result, the test may start to display a positive line. After the allotted time has passed, you should discard the pregnancy test to avoid confusion. Faint Test Lines If you follow all of the instructions correctly, you may notice a thin, faint test line that appears within a few minutes. It can seem at first that the line is too faint to count, but after 10 minutes, it darkens. There are several possible explanations for this line: Chemical pregnancy: When implantation of a fertilized egg happens, hCG is produced, even though that egg may not be viable. Chemical pregnancies are the most common cause of early miscarriage. Without taking a pregnancy test, the miscarriage may easily be mistaken for a regular period. Lower sensitivity test: You might need a test with higher sensitivity levels so that you can get accurate results earlier in the pregnancy. Look for "early results" indicated on the test label. 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. Too much fluid: You can dilute your urine sample if you are urinating too frequently or drinking too many liquids—this is why first-morning urine samples are recommended for pregnancy testing. If you are still unsure about pregnancy test results, try waiting a day or two to take another test. Always use a sample from your first-morning urine (which is more likely to have higher concentrations of the pregnancy hormone, hCG). A Word From Verywell It can very stressful to see conflicting results on a pregnancy test, such as faint lines or evaporation lines. If you're unsure about your results, retest in a couple of days or talk to your doctor about a follow-up blood test for confirmation. Following the directions on your pregnancy test helps avoid the confusion or disappointment of a false positive. Was this page helpful? Thanks for your feedback! Get diet and wellness tips to help your kids stay healthy and happy. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit 3 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. Encyclopedia Britannica. Miscarriage. U.S. Food and Drug Administration. Guidance for over-the-counter (OTC) human chorionic gonadotropin (hCG) 510(k)s - Guidance for industry and FDA reviewers/staff. Cleveland Clinic. Pregnancy tests.