Taking a pregnancy test too early is the most common reason for a misleading result. Knowing how the tests work helps you choose the right day.
How pregnancy tests work
After a fertilised egg implants in the uterus, usually 6 to 12 days after ovulation, the developing placenta starts making a hormone called hCG. Its level roughly doubles every couple of days in early pregnancy. Home tests detect hCG in urine once it reaches a certain level.
The best time to test
- From the first day of a missed period. Most home tests are reliable from this day.
- 21 days after unprotected sex. If you do not know when your period is due, the NHS advises testing at least 21 days after unprotected sex.
- First thing in the morning. Early in pregnancy, morning urine has the highest concentration of hCG.
Can I test earlier?
Some sensitive tests claim to detect pregnancy a few days before a missed period. They can work, but a negative result this early is less reliable because hCG may not have risen enough yet. If you test early and get a negative result, test again on the day your period is due.
If your result is negative
If your period still has not started, wait a few days and test again. Irregular cycles can make it hard to know when your period is due. If tests stay negative and you still have no period, see your doctor.
If your result is positive
A positive result is very likely to be correct. Contact your doctor or midwife, keep taking folic acid, and work out your due date. False positives are rare, but can happen after a very early miscarriage or with fertility medicines that contain hCG.
Find your best test day with our When to Take a Pregnancy Test calculator.
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