When is a pregnancy test accurate?
Too early and it will not show
What the test measures
It measures a hormone called hCG. Your body starts making it once a fertilised egg settles into the wall of the uterus.
That hormone nearly doubles every three days. One day really does make a difference — what was invisible yesterday can show today.
When it is accurate
Taken a week or two after a missed period, urine tests are 97–99% accurate. Earlier than that, a real pregnancy can still read negative.
A blood test at a clinic can pick it up before a period is even late, but urine tests are cheaper, faster and accurate enough, so they are the usual choice.
Four things that keep it accurate
Always look for the control mark. It has to appear whatever the result. If it is missing, the test failed and you need another one.
One line, but no period
It may be a false negative — pregnant, but the test says no. This happens when you test too early.
Take another one a week later. If both are negative and your period still has not come, that is the moment to call your doctor.
Two lines
Congratulations. See a doctor as soon as you can. They will confirm it and start the care you need from there.
If you are taking fertility medication, it can cause a false positive. Be sure to mention it.
One more thing worth knowing
Sometimes two lines are followed by bleeding that looks like a period. About 10 in every 100 known pregnancies end in early loss.
And about half of early losses happen because the number of chromosomes was not right — the embryo could not have developed.
It is not something you did wrong. If you have bleeding, do not wait it out — call your ob-gyn.
Logging it in LunaCat
Log › Pregnancy test › Positive / Negative
Saved with the date, so your next appointment can start with when you tested and what it said.
If you got two lines and a doctor confirmed it, switch Settings › Current situation to «Pregnant». LunaCat pauses cycle predictions and the screens change to match.
This article is for reference. Decisions about your body belong with your doctor.
Use your first morning urine — hCG is most concentrated then
Do not drink a lot right before — it dilutes the sample
Check the expiry date
Use a timer — guessing the minutes changes the result
Sources
- Pregnancy Test — MedlinePlus (NIH)
- Early Pregnancy Loss — ACOG