Have questions about using an at-home pregnancy test? We’ve got all your answers.
By Halle Tecco
How does a pregnancy test work?
Pregnancy tests detect a hormone called human Chorionic Gonadotropin (hCG), which can be detected in urine or blood after an embryo implants itself into your uterine wall. hCG is the first detectable sign of pregnancy, and home tests (like the Natalist Pregnancy Test) are an easy and reliable way to determine if you’re pregnant.
How early can I take a pregnancy test?
You can use the Natalist Pregnancy Test starting five days before you expect your period to start. For the most accurate results (over 99%), test three days before your expected period.
If you get a negative result and tested more than three days before your expected period, you could still be pregnant (see chart). We recommend taking another test in a few days. Since it would be really early in your pregnancy, you may not have enough hCG for the test to detect yet. In just two days, your hCG levels will usually double. The more hCG your body makes, the more likely you are to get a positive result.
What time of day should I test?
If you’re testing before your expected period, it’s best to test first thing in the morning (when your urine has a higher concentration of hCG), but you can still test any time of the day. Keep in mind that drinking a bunch of liquid in the few hours before testing can dilute your urine and cause a false negative result (meaning you could be pregnant, but the test will show you’re not).
I have irregular periods. When should I test?
15% of women have irregular periods, which can make it harder to predict when to test. If this is you, try counting at least 14 days from when you had sex. If your test says you’re not pregnant and you think you might be, test again tomorrow or in a few days.
How to interpret pregnancy test results:
After following the instructions to take the test, you can view your results in the test window. The test window shows two lines—one for the control line (C) to make sure the test worked and another, the test line (T), that shows a positive result.
- Positive: If two lines show up, even if the test line (T) is very faint, that’s a positive—or pregnant result.
- Negative: If only the control line (C) shows up, the test didn’t detect hCG. Either you’re not pregnant or it’s too early to test.
- Invalid: If only the test line (T) shows up, or no lines develop, the test didn’t work. This could mean the absorbent tip wasn’t saturated with enough urine, or the test is expired or damaged. Grab another test and try again. If you still get an invalid result, contact us.
I’m pretty sure I’m pregnant, but the test says otherwise. What should I do?
A negative result means the test did not detect hCG in your urine. A false-negative result (when the pregnancy test is negative, but you’re actually pregnant) can happen for two reasons:
- Either your urine was too diluted (don’t drink a lot of liquid for a few hours before testing) or
- It’s too early to detect a pregnancy. If you tested before your expected period, this could be the case. If you feel you’re pregnant, test again in a day or two. hCG levels soar in early pregnancy—doubling every 48 hours. If you miss your period and still get a negative result, see your doctor.
It’s really rare, but if after five minutes you see no lines or only a test line (T), the test either wasn’t saturated with enough urine—or it’s defective or expired (check the wrapper). Throw it out and try again with a new one.
What can affect pregnancy test results?
- Fertility drugs containing hCG (such as Pregnyl* and Profasi**). Drugs containing hCG usually clear your body two weeks post-injection.
- A recent miscarriage or pregnancy, including a chemical pregnancy (a pregnancy loss very soon after implantation). This may give you a false-positive result when you’re no longer pregnant.
- Rare medical conditions that result in the production of hCG unrelated to pregnancy. These include gestational trophoblastic disease, ovarian tumors, and hCG secreted by the pituitary gland during menopause. If you think this could be you, talk to your doctor.
- Following instructions incorrectly.
- Waiting too long to read your results. Results read after 15 minutes aren’t accurate.
I got a positive result but have some bleeding. What’s going on?
Check out this post on spotting by Dr. Mare.
Do you have more questions? Learn more about our pregnancy tests here.