When is the time to take pregnancy test

• There are two main types of pregnancy tests: urine and blood tests.
• Take a home urine test after your next missed period — anywhere from 14 to 18 days after conception.
• Blood tests are more sensitive and can tell you if you're pregnant 6 to 14 days after conception.

You have two options when it comes time to see if you have a baby on board.

The most common is an at-home urine pregnancy test, available over the counter, though you can take a urine pregnancy test at a medical clinic. Another option is a blood test performed at a medical clinic.

"Both tests check for a hormone called human chorionic gonadotropin, or hCG," says Crystal Newby, MD, of Kansas City Ob-Gyn. "This hormone is produced after a fertilized egg attaches to the wall of your uterus."

The egg typically attaches 6 days after fertilization, at which point, hCG levels in your blood and urine will increase for the next 6 to 10 weeks. Once hCG levels are high enough, you can expect an accurate reading, but not before then. 

When should you take a blood pregnancy test? 

Depending on a woman's cycle, a blood test can detect pregnancy between 6 and 14 days after conception.

Blood tests for pregnancy are more sensitive to hCG than home pregnancy tests. They can detect this hormone in low quantities and tell you if you're pregnant sooner than a home test.

While blood tests can provide results sooner than home pregnancy tests, they are usually more expensive and take longer to provide results because the blood must be sent to a lab for analysis. 

If the lab is in-house then it will take a few hours. But if the lab is at a different location, it could take several days to learn the results.

When should you take a home pregnancy test?

Most home pregnancy tests advise you to take the test after you miss your next period. If you have a standard 28-day cycle, you'll be most fertile two to three weeks before your period. 

So if you get pregnant during that fertility window, you'll need to wait at least 14 to 18 days after conception to take a home pregnancy test.

If you get a negative result and suspect you're pregnant, check the instructions on the box. Home pregnancy tests typically recommend retaking the test 5 to 7 days later, when the hCG levels in your body will be higher.

This type of result is called a "false negative." Sometimes you can receive a false negative result if you take a pregnancy test too soon when your hCG levels are too low for the test to detect them accurately.

Moreover, recent miscarriages, fertility drugs, and rare hCG secreting tumors can interfere with the results of at-home urine tests. If you receive conflicting results after taking a home pregnancy test multiple times, doctors recommend a blood test.

How accurate are pregnancy tests?

Blood pregnancy tests are considered by doctors to be 99% accurate. Quantitative blood tests (also called beta hCG tests) are the most accurate blood tests and can help doctors tell the exact age of the fetus and play a role in detecting any abnormalities.

If you follow directions, home pregnancy tests are an estimated 97% to 99% accurate. If you perform a urine pregnancy test in a lab setting, like at your doctor's office, the accuracy will be closer to 99%. It's important to make sure that you check the expiration date on your home test, as it can affect the accuracy of the results.

After taking either a blood or urine test, it's important to confirm the pregnancy with an early ultrasound.

Insider's takeaway

Home pregnancy tests can provide results faster and be more convenient than a blood test. But you'll probably have to wait longer to receive accurate results.

You can expect accurate results from a blood pregnancy test as soon as 6 to 14 days after conception. Because the test must be analyzed in a lab, it could take up to several days to get the results.

To get the most accurate reading from a home urine test, wait until your missed period. This can come anywhere between 14 to 18 days after conception. If you get a negative result, you can try taking a home test again in 5 to 7 days to see if you have higher amounts of detectable hCG in your body.

Blood tests are considered to be 99% accurate, while home pregnancy tests are around 97% to 99% accurate. Regardless, you should confirm your results by getting an ultrasound.

Denice Rackley is a freelance writer for Insider.

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Since the earliest recorded history, women have had a strong desire to know whether they are pregnant as early as possible. The body goes through countless changes in the first trimester, and one of the first indicators is a change in the hormones that leave the body through urine.

Ancient Egyptians relied on a form of urine testing to determine pregnancy status way back in 1350 BCE. A woman urinated daily on wheat or barley seeds and if the plants grew, it meant she was pregnant. Modern-day validation suggests that test was about 70% accurate in detecting human chorionic gonadotropin (hCG), a hormone produced by a woman’s body soon after implantation of a fertilized egg inside the uterus.

Thankfully, urine-based pregnancy tests have evolved substantially. Women now have access to advanced tests that can detect a pregnancy as early as eight days after ovulation. But while many home pregnancy tests are marketed as simple and effective, getting accurate results comes down to how early in your ovulation cycle you take the test.

Ovulation generally occurs around day 15 of a 28-day cycle. In a normal pregnancy, an egg is fertilized in the fallopian tube and then travels into the uterus, where it implants in the uterine wall. After implantation, production of hCG starts from cells in the developing placenta (tissue that will feed the fetus). Trace levels of hCG can be detected as early as eight days after ovulation.

That means you could get positive results several days before you expect your period to start. However, the first part of your cycle is more variable than the second, making it tricky to determine the best time for an early test.

“Thankfully, pregnancy tests have evolved substantially since the 20th century. Women now have access to advanced tests that can detect a pregnancy as early as eight days after ovulation.”

When to take a home pregnancy test

The length of time from the first day of a period to ovulation can vary by several days from month to month. Sexual activity around ovulation leads to the possibility of fertilization of an released egg by sperm. But even then, the time frame for a fertilized egg to implant can vary. And hCG isn’t produced until after implantation has occurred.

For the most accurate results, we recommend testing in the morning on the day you expect your period to start. This allows for variability in the timing of ovulation, fertilization, and implantation. Testing in the morning provides a more concentrated urine sample.

Follow the directions carefully to get the best results. Before you take the test, make sure you understand what the readout for “pregnant” and “not pregnant” will be. Some tests still use two lines to indicate you are pregnant and one to indicate that you aren’t. However, many tests have switched to words such as “yes” and “no”, or “pregnant” and “not pregnant” for additional clarity.

Related reading: Is it OK to use a hot tub during early pregnancy?

Pregnancy test accuracy

Each type of pregnancy test is designed to detect a set minimum level of hCG. This is why pregnancy test manufacturers advertise the way they do: “Know four days sooner,” or “Accurate up to six days before a missed period.” However, while home pregnancy tests are quite accurate – many boast a 99% detection rate based on laboratory testing results – marketing claims can be misleading.

For example, a 99% detection rate means a test can detect hCG 99% of the time on the day you miss your period. These statistics also assume that women are testing at the optimal time and following all instructions correctly.

Many home pregnancy tests available today are midstream urine dip tests, which are the traditional “pee-on-a-stick” tests and are fairly easy to use. There also are tests in which you pee into a cup and dip a test strip into the urine. The New York Times published a story ranking the best home pregnancy tests, citing a midstream test with an ergonomic grip as the easiest to use and most accurate.

Research has shown that average test results when women used the dip tests matched lab test results just 70% of the time, whereas 99% of women typically can get an accurate reading from a midstream test.

False positive and negative results

When a test result is inaccurate, it’s either a false negative (the test says you are not pregnant, but you are) or a false positive (the test says you are pregnant, but you aren’t). Several factors can cause false negative results:

• Having too dilute urine after drinking a lot of water or testing later in the day.
• Testing too soon when there has not been enough time for a fertilized egg to implant and start hCG production.
• Using a pregnancy test that doesn’t detect lower levels of hCG. You can check the package insert for more information about the level at which the test will be positive.

Sometimes an egg will implant briefly but will not be sustained. This is also called a chemical pregnancy – hCG is produced, but the pregnancy doesn’t continue. A test performed several days before an expected period can show a positive result, but the woman still gets her period soon or on time. Rarely, certain tumors can produce hCG, causing a pregnancy test to be positive even when a woman is not pregnant.

Related reading: It's not your fault: Understanding miscarriage

When to see a doctor

Most women who have a positive pregnancy test should wait a week or two before calling the Ob/Gyn office for a pregnancy blood test or ultrasound to confirm the pregnancy. We suggest waiting because the rate of early pregnancy loss is high, and it’s possible that you might have had a chemical pregnancy.

However, women with a history of ectopic pregnancy or current abdominal pain should call the doctor right away to be examined. Ectopic pregnancies implant outside of the uterus and produce hCG, resulting in positive pregnancy tests. However, these pregnancies can cause abdominal bleeding and prompt medical care is necessary. Women who have congenital heart defects or other chronic physical or mental health conditions should also see a doctor right away because treatment plans or medications might need to be altered to protect the woman and the fetus.

Advances in home pregnancy tests give women greater insight into what’s going on in their bodies sooner than ever before. No matter what your childbearing plans might be, it’s essential to get quick, accurate results at home to plan your next steps accordingly.

To visit with an Ob/Gyn, call 214-645-8300 or request an appointment online.