Home Pregnancy Tests: How do They Work & Are They Accurate?

LAST MODIFIED: Thursday, April 25, 2019
Woman Checking Home Pregnancy Test

If you are hoping to get pregnant or believe you may already be pregnant thanks to early pregnancy symptoms, you might be wondering if you should use a home pregnancy test to see if you may have some good news.

But do home pregnancy tests really work? Are they worth trying, and how reliable are they?


FAQ’s About Home Pregnancy Tests

“How do home pregnancy tests work?”

Very soon after conception takes place, your body begins to produce high levels of a hormone called human Chorionic Gonadotropin or hCG. This hormone ensures that your body prepares itself for your pregnancy and very high levels of hCG are characteristic of the first few weeks of pregnancy. A substantial increase in hCG shows up in your urine, and home pregnancy tests measures your hCG levels as a pregnancy indicator.


“How soon after conception will my home pregnancy test pick up a positive result?

If you skipped your period, it’s probably best to wait about a week before trying a home pregnancy test. That’s because every woman is different and so is every pregnancy. The amount of hCG in your urine may or may not be sufficient for you to get an accurate result earlier on. Some home pregnancy test brands claim a 99% accuracy rate from the first day you would have expected your period, but by and large, this reputation for accuracy so early on is exaggerated.


“How can home pregnancy test claim to be so accurate?”

Claims of ‘99% accuracy’ are based on an FDA regulation that allows manufacturers to stipulate accuracy as compared to existing products on the market. If the new product is 99% as accurate as an existing product, the claim of ‘99% accuracy’ can be made. Obviously, this is not the same thing as picking up 99% of pregnancies!


“How do I know if the test I’m using is more or less sensitive to hCG concentrations?”

Check the package to find out at what level hCG will be detected. For example, if the package stipulates a sensitivity of 20 mIU/ml, it will give you a positive result at a lower hCG concentration than one that cites a higher mIU/ml.

Couple with home pregnancy test


“What’s the best way to use a home pregnancy testing kit?”

Check the expiry date on the package before using your home pregnancy test. Bear in mind that such kits should be stored in a cool, dry place, so the bathroom is not the best place to keep them even though it is convenient.

When we wake up in the mornings, our urine is quite concentrated and that’s the best time to perform your home pregnancy test too. Later on in the day, your urine is more diluted, especially if you drink lots of fluids.

Follow the package instructions. Some tests require a few drops of urine placed in a testing compartment while others allow you to urinate directly onto the device. Reading the result also depends on the brand and the type of testing device. In some types, colors are used as indicators, while others use digital readouts to tell you your results. Once again, you’ll find the correct information on the product package. The majority of brands also have a test indicator to tell you whether the device was able to obtain a valid reading. You can’t expect an instant result either. Wait for up to 10 minutes to ensure that the device has time to obtain an accurate reading.

If your test is negative or inconclusive, give it a few more days and then test again. It may be too early to pick up your pregnancy.


“What about false positive results: are they a possibility?”

It’s quite rare to get a false positive result in most instances, but under certain circumstances it can happen. If you had a miscarriage in the last two months or if you have a molar pregnancy, you could get a false positive. Molar pregnancies are very rare: only about 1 in 1500 pregnancies are molar pregnancies. In these cases, the egg is fertilized but develops into a mole rather than a proper embryo.

Since hCG levels are used to determine whether you are pregnant, using hCG as a fertility treatment can confuse your home pregnancy test. In very rare cases, certain types of tumor can also cause a rise in hCG in the bloodstream. Most false positives result from the use of a faulty testing kit or one that has passed its expiry date. However, there’s also the possibility of a chemical pregnancy. In this case, the fertilized egg is unable to develop normally and this results in a very early miscarriage that is most often followed by an unusually heavy period.

See your doctor immediately if you experience feelings of dizziness, have pain in your abdomen or pelvis or experience heavy bleeding.