Pregnancy test: definition and meaning
A pregnancy test detects human chorionic gonadotropin (hCG), a hormone made after a fertilized egg implants in the uterus. Home tests check urine; blood tests at a clinic can detect smaller amounts and measure exact levels. Most home tests are reliable from the first day of a missed period, about 14 days after ovulation.
Types of test
| Type | Detects | When |
|---|---|---|
| Home urine test | hCG above a threshold, often 10 to 25 mIU/ml | From the day your period is due |
| Early-result urine test | Lower hCG levels | A few days before a missed period, less reliable |
| Qualitative blood test | Yes or no | About 7 to 12 days after ovulation |
| Quantitative blood test | Exact hCG level | Used to track early pregnancy |
Getting an accurate result
- Wait until your period is late if you can. Testing too early is the most common cause of a false negative.
- Use first-morning urine if testing early, when hCG is most concentrated.
- Read the result within the time on the instructions; lines that appear later don't count.
- Any line, even faint, within the time limit usually means positive.
A negative test with a late period? Wait a few days and test again. See late period, negative test and use our pregnancy test calculator to find your earliest reliable day. Learn more in hCG and implantation.
The wait
The days before testing, often called the two-week wait, can be stressful whether you're hoping for a positive or a negative. PMS and early pregnancy symptoms overlap, so it's normal to feel uncertain until you test.
Frequently asked questions
Can a pregnancy test be wrong?
False negatives are common when testing early. False positives are rare, but can happen after a recent pregnancy loss, with some fertility medicines, or with a chemical pregnancy.
How soon after sex can I take a pregnancy test?
Not for at least 2 weeks. Implantation and the rise in hCG take time, so 3 weeks after sex is more reliable.
Sources
This page is for information only and isn’t medical advice. If something worries you, please talk to a doctor.
Keep reading
When to take a pregnancy test: find your most accurate dayWhen to take a pregnancy test: enter your last period and cycle length to see the earliest testing day and the day a result is most reliable.When should you take a pregnancy test?How soon can you take a pregnancy test? Most work from the first day of a missed period. When early tests work, best time of day, and when to test again.Human chorionic gonadotropin (hCG): definitionhCG is the hormone made after implantation that pregnancy tests detect. How fast it rises, what beta hCG numbers mean, and when a test can turn positive.
Implantation: definition and meaningImplantation is when a fertilized egg attaches to the lining of the uterus, usually 6 to 10 days after ovulation. What happens, timing and signs.Late period but a negative pregnancy test?Late period but a negative pregnancy test? You may have tested early or ovulated late. Other common causes, when to retest, and when to see a doctor.