Do Expired Pregnancy Tests Still Work?

When you're unsure whether or not you're pregnant, the last thing you want to do is make another trip to the store to buy a pregnancy test if the one you have stashed away in your bathroom has expired. However, paying attention to that date on the box and on the individual wrappers inside is important. A chemical in each pregnancy test checks for the hCG (human chorionic gonadotropin) hormone that's found in your urine. In most cases, hCG is only present if you're pregnant. However, when a test is past its expiration date, that chemical isn't guaranteed to detect hCG hormones.

That means, if you use an expired test, you might get a false negative. You may be pregnant, but the test isn't accurately detecting the hormone. Although it's entirely possible you'll still get an accurate, positive result, that could be because the chemical hasn't broken down yet, or the brand you chose had a higher sensitivity to hCG.

While using an expired test isn't harmful, it's a good idea to buy a new test whose results you can trust, so you don't have to doubt. Beyond keeping tabs on expiration dates, proper storage will help ensure accurate results. Ideally, tests should be stored at 59 to 86 degrees Fahrenheit. Just like with many medicines, the bathroom isn't the best spot, even if it's the most convenient. This sometimes-steamy space can shrink the chemicals' shelf life. A similar situation could arise if you bought tests and left them in a hot car for a prolonged time. Although pregnancy tests can be surprisingly resilient, it's not worth compromising your own peace of mind.

Like with many other things in life, it's important to follow the directions on a pregnancy test. Some tests can detect lower levels of hCG and can be taken early, days ahead of a missed period. However, if you're looking for the most accurate results, wait a few more days to allow hCG levels to rise. Similarly, if urine is more diluted because you drank a lot of liquids, your hCG levels may be diminished as well. This is why tests often recommend waiting until first thing in the morning. To ensure a sufficient amount of urine gets onto the test, you can use a cup to collect it. 

On the other hand, if you wait too long to check the results, they could be misleading. Typically, after about 10 minutes, an evaporation line may appear as the wet test strip starts to dry. Although these lines often look less distinct than a positive result, they could still introduce doubt.

Some tests have features to help minimize these pitfalls, like a digital readout that says "pregnant" or "not pregnant" instead of colored lines, or even an indicator to confirm enough urine has saturated the strip. However, since these may cost slightly more, compared to a traditional test from the same brand or Dollar Tree pregnancy tests, some people believe the extra bells and whistles aren't worthwhile. In the end, no matter the test you select, using it before it expires is one of the best ways to avoid inaccurate results.