Taking a home pregnancy test is straightforward: you either hold the test’s absorbent tip in your urine stream for 7 to 10 seconds or dip it into a collected sample for at least 10 seconds, then wait about 5 minutes for the result. The timing of when you test, how you prepare, and how you read the result all affect whether you get an accurate answer.
When to Take the Test
Home pregnancy tests detect a hormone called hCG, which your body starts producing after a fertilized egg implants in the uterus. At 3 weeks after your last menstrual period (roughly a week before your expected period), hCG levels can be as low as 5 mIU/mL. By week 4, when your period is due, levels range from 5 to 426 mIU/mL. That wide range is why testing too early often gives a false negative: your body may not have produced enough hormone yet for the test to pick up.
The most reliable time to test is the day of your missed period or later. If you get a negative result but still suspect you’re pregnant, wait a few days and test again. By week 5, hCG levels jump to 18 to 7,340 mIU/mL, making a positive result much harder to miss.
Why First Morning Urine Matters
Your first urine of the day is the most concentrated because your kidneys have been filtering all night without dilution from drinking water. That concentrated sample contains the highest amount of hCG, giving the test the best chance of detecting it. If you drink a lot of fluids before testing, you dilute the hormone and risk a false negative. This is especially important in early pregnancy, when hCG levels are still low. If you can’t test first thing in the morning, try to avoid heavy fluid intake for a couple of hours beforehand.
Step-by-Step Testing Process
Every test brand has slightly different instructions, but the basic process is the same. You have two options for collecting your sample:
- Midstream method: Remove the cap from the test stick, hold the absorbent tip directly in your urine stream for at least 7 to 10 seconds, then lay the test flat on a clean surface.
- Dip method: Urinate into a clean, dry cup. Dip the absorbent tip into the urine for at least 10 seconds, then remove and lay flat.
After collecting the sample, wait about 5 minutes for the test to process. Don’t peek early and don’t tilt or shake the test. Set a timer so you read the result in the correct window.
Reading the Results Correctly
On a traditional line test, one line (the control line) confirms the test is working. A second line, even a faint one, indicates a positive result, as long as it has color. That color may be pink or blue depending on the brand, but it should be visible and run the full width of the result window.
An evaporation line is a common source of confusion. It appears as a colorless, grayish, or shadowy streak in the result window after the urine dries. If the second line has no real color, doesn’t match the width of the control line, or doesn’t stretch from top to bottom of the window, it’s likely an evaporation line, not a positive.
To avoid this problem, read your result within the timeframe specified in the instructions. Waiting longer than 10 minutes allows urine to dry on the strip, which can leave that misleading mark. If you’re unsure whether a faint line is real, test again in two days. If you’re pregnant, rising hCG levels will produce a clearer line.
Not All Tests Have the Same Sensitivity
The biggest difference between brands is how much hCG they need to detect before showing a positive. A comparative study found that First Response Early Result had a sensitivity of 6.3 mIU/mL, detecting over 95% of pregnancies on the day of a missed period. Clearblue Easy Earliest Results required 25 mIU/mL, catching about 80% of pregnancies at the same point. Five other products needed 100 mIU/mL or more, detecting 16% or fewer of pregnancies that early.
If you’re testing before or on the day of your missed period, a more sensitive test makes a real difference. If you’re testing a week or more after your missed period, nearly any test will work because hCG levels have risen high enough for all of them to detect.
Digital Tests vs. Line Tests
Digital tests display the words “Pregnant” or “Not Pregnant” instead of lines, which eliminates the guesswork of reading faint lines or worrying about evaporation marks. Some digital tests can detect hCG at levels as low as 10 mIU/mL, while many traditional line tests require 25 mIU/mL. The underlying technology is the same: both measure hCG in your urine. The trade-off is that digital tests cost more and have a battery-powered display that can fade over time, so they’re not ideal if you want to keep the test as a keepsake.
What Can Cause a False Positive
False positives are uncommon, but certain medications can trigger one. Fertility drugs that contain hCG are the most direct cause, since they introduce the exact hormone the test is looking for. Some anti-seizure medications, certain antipsychotics, anti-nausea drugs, and even some antihistamines have also been associated with false positive results. Progestin-only birth control pills can occasionally cause one as well.
A very early miscarriage, sometimes called a chemical pregnancy, can also produce a true positive followed by a period arriving a few days later. In this case, the test correctly detected hCG from a pregnancy that didn’t continue.
What Can Cause a False Negative
False negatives are more common than false positives, and the usual reason is testing too early. If implantation happened later than average, your hCG levels may not have reached the test’s detection threshold yet. Other causes include diluted urine from heavy fluid intake, using a test that’s expired, or not holding the absorbent tip in the sample long enough.
If you get a negative but your period still doesn’t arrive, test again in two to three days. hCG roughly doubles every 48 hours in early pregnancy, so even a short wait can make the difference between a negative and a clear positive.
Accuracy Claims on the Box
Most pregnancy tests advertise “over 99% accurate,” but that number comes with context. The FDA caps accuracy claims at 99% and specifically prohibits language like “virtually 100% accurate” or “100% accurate.” That 99% figure typically applies when the test is used correctly on or after the day of a missed period. Test earlier than that, use diluted urine, or misread the result window, and real-world accuracy drops. The test itself is reliable; most errors come from timing and technique.