When my patients are trying to conceive, I hear the same story: I took a home pregnancy test every day for a week just to make sure. This happens both when the test is negative and positive.
What if you could save that time and anxiety and make your home pregnancy test a “one and done” situation?
I encourage my patients to do that – to save doubt, decrease anxiety, and don’t forget – to save money. With home pregnancy tests as expensive as $10 a pop, the money part can certainly add up.
What is a home pregnancy test and how does it work?
Home urine pregnancy tests (or UPTs, as we call them) are checking for the pregnancy hormone beta HCG –this is the beta subunit of the hormone human chorionic gonadotropin. Sometimes this hormone is abbreviated “beta”, or “HCG”, or written as “bHCG”, as I will refer to it. When we’re talking about pregnancy tests, they mean the same thing.
bHCG is secreted in the blood by a developing pregnancy after implantation occurs. Implantation can occur as early as 6 days after ovulation, is most commonly 8-10 days, but can be up to 12 days after ovulation. From there, we expect the bHCG levels to increase. A general rule of thumb is hormone levels increase 2X every 2 days.
bHCG can be detected in both the urine and blood. In studies, the urine level is about 20% of the blood level. This means the blood draws can tell earlier if implantation has occurred. However, the cost and utility of knowing this early is limited. Most doctors use blood bHCG levels when an ectopic pregnancy is suspected – we monitor the bHCG level every 48 hours to make sure it is rising as expected for early pregnancy. If it’s not, an ectopic pregnancy needs to be considered. (Too much to cover in this article, but I don’t want to leave you hanging: ectopic pregnancies are pregnancies that implant outside the uterus. They can be very dangerous and will never develop into a normal pregnancy. Thankfully this only happens 2% of the time. If you have pain and bleeding – both of which can also be common in normal early pregnancies – your doctor may recommend you have blood tests to check the bHCG levels. Ultrasound isn’t great at detecting ectopics this early in pregnancy).
But back to home pregnancy tests and the question for this article:
How can I make a home pregnancy test the most accurate? So I only have to take 1 to get the right answer?
When is the optimal time to take a home pregnancy test for you? It depends. Did implantation occur 6 days after ovulation, or 12? Or somewhere in between? It’s impossible to know. Is your bHCG doubling every 48 days, or is it slower than that but still normal? Impossible to know!
With this many variables that are impossible to know, we intentionally lump everyone into this one recommendation: if your period does not come on the day expected, time to check a home UPT. If your cycle length is variable, such as every 28-30 days, assume your cycle is long and check on day 31.
I know (and remember clearly) the urge to take a test before the date of missed period because of the anticipation of “what if I’m pregnant?!!”. But truth be told, the sooner you take the test, the more likely you’ll get a false negative and be in the group of spending $50+ for the sake of not following my advice. Which home UPT are you using?
2. Different home UPTs have different accuracy!
One study – one of my favorites of all time (here’s my blog entry about this study in particular) – compared First Response to Clear Blue to EPT and found First Response was the clear winner for most accurate detection.
Also surprisingly important: the ease of following instructions and interpreting the test. Not following instructions for the specific test can make the results unreliable. Sometimes it’s hard to get the right amount of urine. Waiting too long to check the results can cause false results too. Interpreting the lines can be harder that you think! People try to make how dark the line is mean something, and that’s not how we determine levels of bHCG.
I like the digital yes/no, positive / negative best. Straightforward answer, little room for interpretation. Even the happy or unhappy faces bother me because guess what? Not everyone has a smiling face when they find out they are pregnant.
3. Follow instructions!
Repeating myself here but read and follow instructions of the test you are using. Follow those, not what you’ve seen on TV.
4. Concentration of urine matters!
Take the test with the first pee of the morning. That is typically the most concentrated urine of the day. If urine is dilute, the amount of bHCG in the urine will also be dilute – potentially enough to make the test negative when it should be positive.
5. Consider body weight
bHCG levels tend to be lower in early pregnancy for females that are obese. If your BMI is 30+, consider waiting a few more days.
6. Repetition is not always helpful
Repeating a home UPT is helpful in one situation: you have a negative test and your period still does not come. Repeating the test 3-4 days later may give you a different answer. In this case, the first negative test was a false negative because your bHCG was not high enough. Waiting increased the bHCG level enough to finally be detected.
Repeating a home UPT when you have a positive result is not helpful. You are pregnant. A repeat test a few days later doesn’t tell you that you “are more pregnant” or “still pregnant”. Call your doctor and make an appointment. Unfortunately miscarriages do happen, but checking a home UPT does not tell you if you’ve had a miscarriage or not. See your doctor in this situation.
I am a board certified OBGYN at Cedars Sinai in Los Angeles.
I am co-founder of Female Health Education, a platform offering digital courses, striving to empower females through health education.
My passion is promoting and demystifying health information to the public. My blog, Dr. Sara Twogood’s LadyParts Blog, provides comprehensive information about fertility, pregnancy, and gynecology topics. I am on the medical board for the period tracker app Flo; contribute as a medical expert for pregnancy app and website The Bump; and serve on the Byrdie Beauty and Wellness Review Board (Byrdie.com). I have been featured as an expert for the podcasts The Dream and Her body, Her Story and quoted in numerous online and print publications.
I am honored to be named “Top Doctor” in Los Angeles magazine for years.