Home pregnancy tests are more reliable than people give them credit for. Boxes love to quote "over 99% accurate", and that holds, but only if you test at the right time and follow the directions. Most "wrong" results trace back to timing, not a dud test.
What that 99% figure actually means
The famous 99% almost always means detecting a pregnancy from the day your period is due. Go earlier and accuracy slides, simply because there may not be enough hCG yet to register. Picking the right day with the pregnancy test timing calculator is the easiest way to get a result you can believe.
Why false negatives happen
A false negative, where the test says no but you are actually pregnant, is the more common slip-up. The usual reasons:
- Testing too early, before hCG has had time to climb.
- Watered-down urine after drinking a lot. First-morning urine is the most concentrated.
- Reading the result late, outside the window the instructions give you.
Negative test but no period? Give it 2 to 3 days and try again.
Why false positives are rarer
A false positive is much less common. It can crop up after a recent miscarriage or chemical pregnancy, when leftover hCG is still in your system, with certain fertility drugs that contain hCG, or from reading an "evaporation line" once the test has dried out. By and large, a clear positive is the real thing.
Confirming it
Treat a positive home test as your cue to call your provider, who can run a blood test and book an early scan to date the pregnancy. From there, the due date calculator and the conception date calculator help you lay out the timeline.
Digital tests, line tests, and that faint second line
Most home tests come in two styles. Line tests show one or two lines, and even a faint second line usually counts as positive, since any visible line means hCG was picked up. Early on that line can be very pale because hCG is still low, so it tends to darken if you re-test a couple of days later. Digital tests skip the squinting and simply read "pregnant" or "not pregnant", though they often need a little more hCG to flip to that word, which can make them slightly less sensitive for very early testing. Whichever you use, reading the result inside the time window on the instructions matters, because marks that show up later can mislead you.
What to do after a positive result
A positive at home is your cue to contact your doctor or midwife rather than the finish line. They can confirm the result, talk through your dates, and usually arrange an early ultrasound to check the pregnancy is in the uterus and to set your due date. In the meantime, if you are not already, start a prenatal vitamin with folic acid and mention any medications you take. A faint or uncertain result is worth re-testing in a couple of days before you read too much into it either way.