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Last updated: Nov 01, 2021
6 min read

When to take a pregnancy test

Urine pregnancy tests need a certain level of hCG hormone before they can detect pregnancy. How accurate your results are depends on how many days past your missed period you are. If you test too early, you might get a false negative result.

Disclaimer

If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

The wait to take a pregnancy test often feels like an exercise in patience. If you test too early, the only thing you might end up testing is your nerves. It’s best to wait until after you miss your period to take a pregnancy test, but if you can’t wait that long, some early pregnancy tests might offer answers a few days sooner. 

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Understanding your fertile days

A normal menstrual cycle ranges from 24 to 38 days long (Fraser, 2007). Day one of your cycle starts on your first day of menstrual bleeding. Ovulation, when the ovary releases an egg, typically happens around the midpoint of your cycle—day 14 in a 28-day cycle (Thiyagarajan, 2021). 

An egg can only survive for up to 24 hours after being released from the ovaries, which means fertilization must happen within that window (Oliver, 2021). However, that doesn’t mean that pregnancy only occurs if you have sexual intercourse on that day.

Sperm typically live for three days on average but can survive for up to five days. Therefore, the window for getting pregnant starts five days before ovulation (ASRM, 2017). 

After fertilization occurs, the egg begins traveling down the tube and into the uterus. Once in the uterus, the fertilized egg attaches to the uterine wall. Implantation typically occurs between 6–12 days after ovulation, with most eggs implanting between days 8–10.

After the egg implants, it starts to produce human chorionic gonadotropin (hCG), the hormone detected by pregnancy tests, almost immediately. Some sensitive pregnancy tests can detect pregnancy at this point, but the majority likely cannot.  

When to take a pregnancy test

As tough as waiting is, the longer you wait to test, the more accurate your results will be. It is possible to get a positive result before your missed period if your hCG levels are high enough. But if you test too early, you run the risk of getting a false negative because you may not have a detectable amount of hCG in your urine (Betz, 2021). 

However, hCG levels vary from person to person, and some people have low hCG levels that can avoid detection until the week after a missed period (Butler, 2001). Reading the label on your pregnancy can help you determine when to take that particular pregnancy test and how accurate it’ll be.

If you are doing fertility treatments, such as in-vitro fertilization, you may have blood drawn at your doctor’s office earlier than you would test your urine at home. It’s best to test your urine when you first wake up and before you drink any water since this is when your urine is most concentrated. Drinking fluids can dilute your urine, making it difficult for pregnancy tests to detect hCG (Betz, 2021). 

Always read the directions on how to take your urine tests. Some tests will ask you to dip the stick in urine, while others will ask you to hold the test in your urine stream. The test’s instructions will also tell you how long the test needs to be in urine and how long you should wait before reading the test results. 

How pregnancy tests work

At-home pregnancy tests work by detecting the pregnancy hormone human chorionic gonadotropin (hCG) in your urine. You can buy pregnancy tests over-the-counter at your local pharmacy. Your healthcare provider can also test for pregnancy by checking the level of hCG in your blood. A stark difference between urine pregnancy tests and blood pregnancy tests is that the former can’t identify the amount of hCG in your body; only blood tests can do that (Betz, 2021). 

Aside from detecting how much hCG your body is producing, blood tests are also more sensitive and can detect lower levels of hCG than urine tests can. The most sensitive urine pregnancy test can detect 6.3 mIU/mL of hCG, making it possible to detect pregnancy shortly after implantation (Cole, 2005). 

A study of urine pregnancy test results found that the most sensitive urine pregnancy tests can detect 95% of pregnancies by the day of your missed period. Other less sensitive pregnancy tests could only detect 16% to 80% of pregnancies on the day of a missed period, depending on their level of hCG sensitivity (Cole, 2005). 

False positives and false negatives

It’s possible to get a false positive pregnancy test (meaning the test is positive, but you’re not pregnant), although that’s rare. Your body produces small amounts of hCG even when you aren’t pregnant, but these levels are not detectable through urine pregnancy tests. The level of hCG found in your blood rises as you age, with levels up to 14 mIU/mL being normal in women over the age of 55. Certain cancers and tumors can also cause high hCG levels (Betz, 2021). 

False negatives (you’re pregnant, but the test says you’re not) are more common due to the range of early hCG levels and sensitivities of urine pregnancy tests. The hCG level in your blood and urine doubles within 48 hours during a healthy pregnancy, so you shouldn’t assume you aren’t pregnant if you get a negative result early on. 

You can continue testing every other day in conjunction with doubling hCG levels. You can also get a negative test if the test is expired or was exposed to liquids, so it’s important to check the expiration date of your tests before using them (Betz, 2021; Cole, 2009). 

When to see a doctor 

Once you get a positive urine test, your doctor may want you to come into the office to confirm the pregnancy with a blood test. If you are six weeks pregnant or more, your healthcare provider can perform a sonogram to confirm the viability of your pregnancy. 

You’ll continue to see your healthcare provider throughout your pregnancy for prenatal care. If you get a positive pregnancy test and start bleeding, see your doctor. In some cases, bleeding may indicate a miscarriage, but not always (Dugas, 2021). It’s important to follow up with your healthcare provider over any concerns you may have. 

If your period is typically regular but is now more than a week late and pregnancy tests are still negative, schedule an appointment with your healthcare provider. Your provider can double-check your urine tests with a blood pregnancy test and perform other blood tests to rule out conditions that can cause fluctuations in your menstrual cycle (Holesh, 2021). 

Waiting can be challenging, but if you want reliable results waiting, unfortunately, is often necessary. If you can’t wait or feel early pregnancy symptoms like sore breasts or fatigue, it doesn’t hurt to take a test. But if you test before your missed period, remember there’s a chance it could be a false negative. So test again if you don’t get your period.

References

  1. American Society for Reproductive Medicine. (2017). Optimizing natural fertility: a committee opinion. Fertility and Sterility, 107(1), 52-58. doi: 10.1016/j.fertnstert.2016.09.029. Retrieved from https://pubmed.ncbi.nlm.nih.gov/28228319/ 
  2. Betz, D., & Fane, K. (2021). Human Chorionic Gonadotropin. [Updated Aug 11, 2021]. In: StatPearls [Internet]. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK532950/ 
  3. Butler, S. A., Khanlian, S. A., & Cole, L. A. (2001). Detection of early pregnancy forms of human chorionic gonadotropin by home pregnancy test devices. Clinical Chemistry, 47(12), 2131-2136. doi: 10.1093/clinchem/47.12.2131. Retrieved from https://pubmed.ncbi.nlm.nih.gov/11719477/ 
  4. Cole, L. A., Sutton-Riley, J. M., Khanlian, S. A., Borkovskaya, M., Rayburn, B. B., & Rayburn, W. F. (2005). Sensitivity of over-the-counter pregnancy tests: comparison of utility and marketing messages. Journal of the American Pharmacists Association, 45(5), 608-615. doi: 10.1331/1544345055001391. https://www.sciencedirect.com/science/article/abs/pii/S1544319115316307 
  5. Cole, L. (2009). New discoveries on the biology and detection of human chorionic gonadotropin. Reproductive Biology and Endocrinology, 7(2009), 1-37. doi: 10.1186/1477-7827-7-8. Retrieved from 
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5139804/ 
  6. Dugas, C., & Slane, V. H. (2021). Miscarriage. [Updated Jun 29, 2021]. In: StatPearls [Internet]. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK532992/ 
  7. Dunson, D. B., Baird, D. D., Wilcox, A. J., & Weinberg, C. R. (1999). Day-specific probabilities of clinical pregnancy based on two studies with imperfect measures of ovulation. Human Reproduction, 14(7), 1835-1839. doi: 10.1093/humrep/14.7.1835 Retrieved from https://academic.oup.com/humrep/article/14/7/1835/2913179#66880285 
  8. Fraser, I. S., Critchley, H. O. D., Munro, M. G., & Broder, M. (2007). Can we achieve international agreement on terminologies and definitions used to describe abnormalities of menstrual bleeding?. Human Reproduction, 22(3), 635-643. doi: 10.1093/humrep/del478. Retrieved from https://pubmed.ncbi.nlm.nih.gov/17204526/ 
  9. Holesh, J. E., Bass, A. N., & Lord, M. (2021). Physiology, ovulation. [Updated May 9, 2021]. In: StatPearls [Internet]. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK441996/ 
  10. Johnson, S. R., Miro, F., Barrett, S., & Ellis, J. E. (2009). Levels of urinary human chorionic gonadotrophin (hCG) following conception and variability of menstrual cycle length in a cohort of women attempting to conceive. Current Medical Research and Opinion, 25(3), 741-748. doi: 10.1185/03007990902743935 Retrieved from https://www.tandfonline.com/doi/abs/10.1185/03007990902743935
  11. Oliver R, Basit H. (2021). Embryology, Fertilization. [Updated May 8, 2021]. In: StatPearls [Internet]. Retrieved from  https://www.ncbi.nlm.nih.gov/books/NBK542186/ 
  12. Thiyagarajan, D. K., Basit, H., & Jeanmonod, R. (2021). Physiology, menstrual cycle. [Updated Sep 18, 2021]. In: StatPearls [Internet]. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK500020/ 
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