Yes, Pregnancy Tests Can Expire. Here's What to Know

Whether you're trying to get pregnant or realize you haven't gotten your period, you might be considering purchasing an at-home pregnancy test. When used correctly, those types of pregnancy tests—yes, the ones where you pee on a stick—are accurate 99% of the time. However, if you use a product that's been sitting around in your medicine cabinet for years, or if you don't follow the instructions carefully, it's possible that the test might not reflect what's actually happening with your body.

We tapped three gynecologists to get the latest information on pregnancy tests, including how they work, if pregnancy tests expire, and whether years-old tests are actually reliable.

How Do Pregnancy Tests Work?

Let's start with the basics. For a majority of pregnancy tests, you likely know that you have to pee on a little stick and wait for the results...but how exactly do they work anyway?

"Pregnancy tests detect the hormone human chorionic gonadotropin (hCG) in a woman's urine," says Carolyn Ross, M.D., OB-GYN and medical advisor at Stix. "This hormone is produced by cells that form the placenta after a fertilized egg implants in the uterus." Your body starts producing hCG about six to 12 days after fertilization.

Whether you pee directly onto the pregnancy test or dip it in a small cup of urine is up to you, but either way, you'll want to be sure that a control line (or its digital counterpart) appears. This tells you that the test is functioning properly. Also note that pregnancy tests are most accurate after you miss your period.

Do Pregnancy Tests Have an Expiration Date?

The typical shelf life of a pregnancy test depends on the brand. According to Stephanie Hack, M.D., OB-GYN and founder of Lady Parts Doctor, the shelf life of a pregnancy test is typically two to three years after the manufacture date. This applies to digital and non-digital varieties.

Pregnancy tests might expire if they're stored in your medicine cabinet for a while. Also, if the product sits on the store shelf for a long time before it's purchased, the expiration date might be closer than you expect. Throw out any pregnancy tests that have passed their expiration date.

Are Expired Pregnancy Tests Still Effective?

After the pregnancy test expires, it's usually not as effective at detecting the hCG hormone, as the chemicals used may degrade or evaporate over time. This can cause false negative pregnancy tests, which happens when the test reads negative, but you're actually expecting a baby. False positives are also possible, but they're less likely in this situation.

In other words, expired pregnancy tests might still be effective, especially if your hCG levels are high, but theres's a greater likelihood of error. You shouldn't rely on an expired pregnancy test for accurate results.

Is My Pregnancy Test Expired?

Wondering how to tell if your pregnancy test is expired? Start by looking for an expiration date on the packaging. Clearblue, for example, includes the expiration date on the bottom of the box, as well as on the foil wrapper of each pregnancy test.

You should always check for an expiration date before using an at-home pregnancy test, especially if it's been sitting in your medicine cabinet for a long time.

It's also important to note that other factors can impact a pregnancy test's effectiveness. For example, excessive heat or cold—as well as high humidity—can compromise the integrity of the test, so you should always store at-home pregnancy tests in a room-temperature, dry place. Refer to the product packaging for more information about proper storage.

Do Pregnancy Tests Ever Give False Positives or Negatives?

The short answer is yes, at-home pregnancy tests can give false positives and false negatives. According to Dr. Hack, some of the most common reasons for false positive pregnancy tests include certain medications, medical conditions, or taking the test too soon following a miscarriage or previous pregnancy.

As for false negatives, that may occur if you take a test too early. It's understandable if you're eager to know, but you'll get the most accurate results if you wait. "A false negative may mean that your urine HCG levels may not be high enough for detection," says Heather Jones, M.D., OB-GYN at Maiden Lane Medical in Brooklyn.. "The best time to take a test is one to two days after a missed period." False negatives are also possible if you're using an expired pregnancy test.

If you have lingering questions or worries, it may help to contact an OB-GYN or health care provider to review any concerns and questions you may have. And if you think you could be pregnant, or find yourself with a positive pregnancy test, it's always a good idea to pay a health care professional a visit to confirm with a blood test in the office.