When Is a Pregnancy Blood Test Needed?

If you suspect you may be pregnant, a valuable diagnostic tool that can provide early confirmation is a pregnancy blood test. Unlike the popular urine test (or peeing on a stick), pregnancy blood tests can offer critical information about an early pregnancy.

But for some, it can feel daunting to receive a blood test, or confusing knowing if it’s necessary to get one. Here’s everything you need to know about why and when to get a blood test for pregnancy, as well as their benefits and drawbacks.

What Is a Pregnancy Blood Test?

A pregnancy blood test, also known as a beta-human chorionic gonadotropin (hCG) test, measures the levels of hCG hormone in a person’s blood. This hormone is produced by the developing placenta after fertilization occurs.

A pregnancy blood test is quantified rather than just qualified as positive or negative. This means it can also provide information to support both whether a pregnancy is viable and estimated gestational age based on serial hCG levels.

How Soon Can a Pregnancy Blood Test Detect Pregnancy?

Blood tests typically provide an accurate detection of early pregnancy. They can detect it as soon as about seven to 12 days post conception–even prior to experiencing a missed period. Further, hCG can be detected as soon as six days after ovulation.

The reason: hCG concentration in the blood is higher than that in urine.

“If you or your doctor wants to know if you are pregnant, the blood test can give you results earlier than a urine pregnancy test. The test is also more accurate than urine, especially early on when hCG levels are low,” explains Leslie Saltzman, D.O., a physician and chief medical officer of Ovia Health, a platform helping people navigate fertility and pregnancy issues.

While a home pregnancy test can pick up levels of hCG close to about 20 mIU/mL, pregnancy blood tests can pick up levels as low as 5 mIU/mL.

What Are the Benefits of a Pregnancy Blood Test?

There are several benefits in getting a pregnancy blood test, according to Dr. Saltzman, including the following:

Early detection. For those who want to confirm pregnancy as soon as possible, especially when undergoing fertility treatments or monitoring early pregnancy health, this test offers an advantage compared to urine tests. At-home urine tests are most accurate after a missed period, while blood tests can offer positive results sooner.

Health concerns. Blood tests can be used to evaluate pregnancies, according to Dr. Saltzman. For individuals with a history of miscarriages, or in circumstances where an ectopic pregnancy is suspected, the blood test can monitor relevant hormonal levels to ensure the health of both the birthing parent and the fetus and to get more clarity around gestation status.

According to Ruth Arumala, D.O., M.P.H., a board-certified OB-GYN and the co-chief medical officer of Zuri Fertility, blood tests can also diagnose and track pregnancies of unknown location, which is when someone has an early pregnancy that is not visible on an ultrasound.

What Are the Cons of a Pregnancy Blood Test?

As with any form of testing, there are certain drawbacks to consider. According to Dr. Arumala, the downsides of getting a pregnancy blood test may include:

Cost and accessibility. Blood pregnancy tests are typically performed at a medical provider’s office or in a lab, notes Dr. Saltzman. For some families, pregnancy blood tests may involve additional costs and therefore be less accessible. And, unless you need to know about a pregnancy immediately for health concerns or fertility treatment purposes, a blood test may be unnecessary so early on.

Bruising or pain. For some, Dr. Saltzman explains that pain or bruising can be a consequence of the blood draw. Similar to any other testing that requires drawing blood, it’s important to gauge your own individual response and how you typically feel when getting other blood tests.

False results. You may also continue to test positive following the loss of a pregnancy, either through a miscarriage, abortion, or an ectopic pregnancy, which is a medical emergency caused when a fertilized egg implants somewhere other than the uterus—commonly in a fallopian tube. A confirmation of a pregnancy in these circumstances may be misleading.

How To Handle Results You Weren’t Anticipating

Handling unexpected pregnancy blood test results can be emotionally taxing and the response will depend on the individual. Dr. Arumala recommends taking a deep breath and asking your provider questions. If you are unsure what to ask, let them know and request additional support or resources. 

“You may need some time to deal with your emotions prior to accepting the information given–that’s OK,” says Dr. Arumala. “Make sure, however, you seek help and accept support.”

On the other hand, Dr. Saltzman notes that if you are expecting a positive result due to a missed menstrual period, but the result is negative, you should repeat the test after 48-72 hours for confirmation. The levels of hCG should rise within that time if you are pregnant. 

“If you continue to receive an unexpected result, you should consult your primary care provider or OB-GYN to determine the best course of action,” adds Dr. Saltzman.

Regardless of the outcome of the pregnancy blood test, there are options available. It’s important to always speak with your provider and get all the support you need to navigate whatever you may be feeling.