Home pregnancy tests detect a hormone called hCG in your urine, and most are about 99% accurate when used on or after the first day of a missed period. The process takes about five minutes from start to finish. Getting a reliable result comes down to timing the test correctly, following a few simple steps, and knowing how to read the result window.
When to Take the Test
After a fertilized egg attaches to the uterine lining (usually 6 to 12 days after ovulation), your body starts producing hCG almost immediately. But the initial amount is tiny. Levels double every 48 to 72 hours in a healthy pregnancy, which means it takes several days before there’s enough hCG in your urine for a test to pick it up.
For the most reliable result, wait until the first day of your missed period. Testing earlier is possible with certain brands, but accuracy drops the earlier you test. Not all home tests are equally sensitive. In lab comparisons, First Response Early Result detected hCG at concentrations as low as 6.3 mIU/mL, while most other brands required 100 mIU/mL or more. That’s a huge gap. If you want to test before your missed period, choosing a test specifically labeled “early result” matters.
Time of day also makes a difference, especially if you’re testing early. First-morning urine is the most concentrated, so it contains the highest levels of hCG. Drinking a lot of water before testing can dilute your urine enough to cause a false negative. If you can’t test in the morning, try to wait at least two hours after drinking fluids so your urine has time to concentrate again.
Step-by-Step Instructions
Home pregnancy tests come in two basic formats: midstream sticks and dip strips. Both work the same way chemically. The difference is just how you get urine onto the test.
Midstream method: Remove the cap from the absorbent tip and hold it directly in your urine stream for 7 to 10 seconds. It takes that long to absorb enough of a sample. Then lay the test flat on a clean surface and wait.
Dip method: Collect urine in a clean, dry cup. Dip the absorbent end of the test strip into the urine for at least 10 seconds, then remove it and lay it flat.
With either method, wait the full time specified in your test’s instructions before reading the result. Most tests need about five minutes. Reading it too early can give you an incomplete result, while reading it too late introduces a different problem (more on that below).
How to Read the Results
Most tests display results as lines in a small window. One line (the control line) appears automatically to confirm the test is working. A second line means the test detected hCG, which is a positive result. Some digital tests skip the lines entirely and display “Pregnant” or “Not Pregnant” on a screen.
A faint second line still counts as a positive. This usually just means your hCG levels are still relatively low, which is common in very early pregnancy. What matters is that the line has visible color matching the control line, even if it’s lighter or slightly blurred.
Evaporation Lines vs. Faint Positives
This is the most common source of confusion. If you read the test after the recommended window (typically past 10 minutes), the drying urine can leave a faint streak that looks like a second line. These evaporation lines are usually colorless: gray, white, or shadowy rather than pink or blue. A true positive will have color. If you see a faint colorless mark and you checked the test late, it’s likely an evaporation line and not a real result. Take another test and read it within the correct time window.
What Can Cause Wrong Results
False Negatives
A false negative (the test says you’re not pregnant when you are) is more common than a false positive. The usual reasons:
- Testing too early. There isn’t enough hCG in your system yet. Waiting a few days and retesting often solves this.
- Diluted urine. Drinking a lot of water before testing lowers the concentration of hCG. Use first-morning urine for the best accuracy.
- Using a low-sensitivity test. Standard-sensitivity tests need hCG levels around 100 mIU/mL to show a positive, while early-detection tests can pick up levels as low as 6 mIU/mL. In the first days after a missed period, that difference can be the gap between a positive and a negative.
In rare cases, extremely high hCG levels (far into a pregnancy) can actually overwhelm a home test and produce a false negative. This is called the hook effect, and it happens when the hormone concentration is so high that it saturates the test’s antibodies. This is uncommon and really only relevant if you’re testing well into a pregnancy for some reason.
False Positives
A false positive (the test says pregnant when you’re not) is rare, but certain medications can cause one. Fertility treatments that contain hCG are the most common culprit, since the test is literally detecting the injected hormone. Some antipsychotic medications, certain anti-seizure drugs, anti-nausea medications, and even some progestin-only birth control pills have also been associated with false positives.
A very early pregnancy loss (sometimes called a chemical pregnancy) can also produce a positive result followed by a period. In this case the test was technically correct at the time you took it.
Blood Tests as an Alternative
If you need earlier or more precise results, a blood test from a lab can detect pregnancy as early as six to eight days after conception, well before a missed period. Unlike home urine tests, which only tell you whether hCG is present or absent, a blood test measures the exact amount of hCG in your system. This makes it useful for confirming a pregnancy, tracking how levels are progressing, or clarifying an ambiguous home test result.
For most people in a straightforward situation, a home urine test taken on the day of a missed period with first-morning urine is accurate and sufficient. If you get a negative result but your period still doesn’t come, wait two to three days and test again. The rapid doubling of hCG in early pregnancy means a few days can make the difference between a negative and a clear positive.