Some tests are very sensitive and can show if you are pregnant before your period is due.

However, it is best to wait until at least the first day of a missed period to take any test. For a more accurate result, take the test a week after your missed period.

The reason you shouldn’t take a test too soon is that pregnancy tests work by measuring levels of HCG, a hormone that is only present if you’re pregnant.

The body only releases HCG if a fertilized egg attaches to the uterus in a process known as implantation. Implantation usually happens around 10 daysTrusted Source after conception, when the sperm fertilizes the egg.

Traces of HCG are present from 6 days after implantation, but it typically takes 7–10 days after implantation for the body to build up enough HCG to show up on a test.

If you have an irregular cycle and don’t know when your period was due, it’s best to take the test at least 21 days after having unprotected sex.

You may receive an inaccurate result if you take the test too early in your cycle.

Whether you are trying to conceive or are concerned that your birth control went wrong, a pregnancy test can help confirm if you are pregnant or not. But, taking it too soon might give a false result.

OTC pregnancy tests typically test your urine for HCG hormone.

How you test your urine will depend on the kit you choose.

You may have to:

• collect your urine in a cup and dip a testing stick into the liquid
• collect your urine in a cup and use an eyedropper to move a small amount of fluid into a special container
• place the testing stick into the area of your expected urine stream so that it will catch your urine midstream

According to the Office on Women’s Health, home pregnancy tests are almost 99%Trusted Source effective if you use them correctly.

You can do the test in the privacy of your own home. Simply open the test, follow the instructions, and wait for the recommended time to view the results.

After the recommended waiting time has passed, the tests will display your results in one of the following ways:

• a change in color
• a line
• a symbol, such as plus or minus
• the words “pregnant” or “not pregnant”

Most tests will give a result within a few minutes.

HCG Pregnancy Test Cassette

Here are some signs that you should take a pregnancy test.

1. You’ve missed your period

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One of the first and most reliable signs of pregnancy is a missed period.

If you don’t track your cycle closely, it might be hard to determine whether or not you’re late. A 28-day menstrual cycle is typical, but cycles can vary from 24–38 daysTrusted Source. Consider taking a test if it’s been more than a month since your last period.

Remember that other factors, besides pregnancy, can delay a period or cause you to miss one. They include stress, some medications or medical conditions, changes in birth control, and so on.

It’s also common to experience light bleeding or spotting in the early weeks of pregnancy as the egg buries deeper into the uterine lining during implantation. This may resemble a light period but does not follow the usual pattern or timing. Take note of any difference in the color, texture, or amount of blood, and seek medical advice if you have any concerns.

Always speak with a doctor if you have bleeding and a positive pregnancy test.

What are some other reasons your period might be late?

2. You have cramps

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Implantation can produce a feeling similar to menstrual cramps. In early pregnancy, you may feel this discomfort and think your period is just around the corner, but then it never comes.

If this happens, consider taking a test.

What else causes abdominal cramps?

3. Your breasts hurt

As pregnancy progresses, your body will produce more and more estrogen and progesterone. These hormones will start to make changes in your body to support the baby’s growth.

Your breasts may feel tender and appear bigger due to increased blood flow. Your nipples might hurt, and the veins might look darker under the skin.

This is also common in the days leading up to a period, so it won’t necessarily mean you are pregnant.

What are some other reasons for breast pain?

4. You’re feeling different

Along with cramps and sore breasts, early pregnancy can cause:

• nausea
• food aversions
• exhaustion
• frequent urination

As the weeks go on, these symptoms may get stronger before your HCG levels even out late in the first trimester. You know yourself, so pay attention to your body. Any unusual changes could prompt you to take a pregnancy test.

5. Your birth control method failed

Birth control pills, condoms, and other methods don’t provide 100% protection from pregnancy. There’s always a slight chance of pregnancy, no matter how careful you are.

Birth control pills, for instance, can be over 99% effective if you always use them correctly. But, perfect use is not always possible. Realistically, they are around 91% effective.

Similarly, condoms can break and tear. Male condoms can be 98% effective with perfect use, but they are, in fact, only 82% effective with typical use.

Long-term methods, such as an intrauterine device (IUD), are more reliable and still reversible.

Even if you are using birth control, it is worth having a pregnancy test if you have other signs that could indicate pregnancy.

What’s the best birth control method for your lifestyle?