How Accurate Is an hCG Blood Pregnancy Test?

Blood tests are more sensitive than urine tests, but errors can still occur

Photo illustration of vials of blood

Verywell / Photo illustration by Michela Buttignol / Getty Images

People who are trying to conceive may wonder if a blood pregnancy test can be wrong. These tests, which are done at a doctor's office or in a lab, are over 99% accurate. Blood tests confirm pregnancy by checking for the presence of the hormone human chorionic gonadotropin (hCG), which increases exponentially after conception.

Another common question is whether you can have a negative hCG blood test but still be pregnant. This situation is quite rare, but it is possible to have a false-negative result, particularly if the test is done too early or if the test is faulty.

While at-home urine tests are also extremely accurate, blood pregnancy tests are more sensitive and can detect a pregnancy earlier. Blood pregnancy tests yield a positive result if they detect 1 to 2 mIU/mL (milli-international units per milliliter) of hCG, while urine tests require hCG levels to reach 20 to 50 mIU/mLs.

Blood Pregnancy Test Accuracy

A urine pregnancy test is just as accurate as a blood test (99%), as long as you wait the recommended amount of time to take it. HCG doubles every couple of days in the very early stages of pregnancy. Urine tests can produce a false negative if the urine is diluted (from over-hydration) or the test is taken too early.

As with home urine tests, it is possible (although rare) to end up with false results (both negative and positive) from a blood pregnancy test.

False Negative Results

A false negative means the test is negative, indicating you are not pregnant, but you actually are pregnant. This result can occur if the blood pregnancy test was performed too early, when there is not enough hCG in the blood to detect a pregnancy.

However, once you reach nine to 14 days pregnant, it's very unlikely to get a false negative result. If you believe that you got a false negative from testing too soon, your doctor may repeat the test after 48 to 72 hours.

Beyond testing too early, a false negative blood test can occur if there is a condition called gestational trophoblastic disease. In this case, the lab will need to dilute the sample before performing the test to get an accurate result.

False Positive Results

A false positive test means that the test reads positive—it says you're pregnant—but you're not. This happens very rarely. You may get a false positive if you are taking a medication that contains hCG (such as when undergoing fertility treatments) or due to certain medical issues. Possible causes of a false positive may include:

  • Antibodies present in the blood due to exposure to certain animal products (called heterophile antibodies)
  • Blood or plasma transfusion
  • Taking hCG for weight loss, doping, or fertility
  • IgA deficiency
  • Kidney failure
  • Rheumatoid factors
  • Some types of cancer

Reasons to Take a Blood Pregnancy Test

Blood pregnancy tests are more sensitive than urine tests. They are typically used for those facing infertility or a suspected miscarriage.

A blood test can confirm pregnancy as early as 9 days after conception. Urine pregnancy tests take at least 10 days or longer.

Blood pregnancy tests have to be taken at the doctor's office. Your doctor might advise you to wait until a missed period to do any type of pregnancy testing so you can get the most accurate result. Testing too early can produce a false negative.

Unlike home pregnancy tests, blood tests don't give immediate results. You'll have to wait for a blood pregnancy test result to come back from the lab.

Qualitative vs. Quantitative Testing

There are two types of blood pregnancy tests, both of which offer highly accurate results.

A qualitative blood serum test confirms whether or not hCG is present in the blood, basically offering a yes (you're pregnant) or a no (you're not pregnant) result. The qualitative hCG blood test is about as accurate as a home urine test.

A quantitative blood serum test is also known as the beta hCG test. It measures the exact amount of hCG in your blood. Because this test can detect even trace amounts of hCG, it is highly accurate. Doctors use this test, along with ultrasound, to diagnose an early pregnancy loss.

Disadvantages of Blood Pregnancy Tests

Even though a blood pregnancy test can be performed earlier than a urine test, it can take longer to receive your results. The timing of results varies from lab to lab and can range from an hour to a few days. Also, while it's rare, a blood pregnancy test result can be wrong.

Blood pregnancy tests must be performed in your doctor's office, taking more time out of your schedule. Blood tests are more expensive than home pregnancy tests (depending on doctor and lab fees). Waiting a few extra days to do a home urine test tends to be more convenient.

Possible Risks

There is very little risk associated with getting a blood pregnancy test. Just as with any blood test, you may feel lightheaded, faint, have excessive bleeding, infection or bruising at the puncture site, and/or hematoma (blood accumulating under the skin).

Since veins and arteries differ in size from one person to another (and from one side of the body to the other), getting a blood sample could be more difficult for some people. In order to get the required blood sample, you might need multiple pricks to locate a vein.

A Word From Verywell

Waiting to find out whether or not you're pregnant can feel like it takes an eternity, especially when you're anxious to get the results. If you're having a blood pregnancy test, however, you can feel confident in the results as they are typically 99% (or more) accurate.

It's best to take your doctor's advice and avoid testing too soon. Home urine tests or in-office blood testing can give you false information when not performed as directed. If you have concerns or suspect a false negative or false positive, talk to your doctor about further testing to confirm your results.

6 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Zinaman MJ, Johnson S, Marriott L. Analysis of human chorionic gonadotropin levels in normal and failing pregnancies [40]. Obstet Gynecol. 2015;125(Supplement 1):21S-22S. doi:10.1097/

  2. Cleveland Clinic. Pregnancy test information.

  3. U.S. Food and Drug Administration. Pregnancy.

  4. Betz D, Fane K. Human chorionic gonadotropin (hCG). In: StatPearls [Internet]. StatPearls Publishing.

  5. American College of Obstetricians and Gynecologists. Early pregnancy loss.

  6. Assi TB, Baz E. Current applications of therapeutic phlebotomy. Blood Transfusion. 2014;12(Suppl1):s75–s83. doi:10.2450%2F2013.0299-12

By Dawn Stacey, PhD, LMHC
Dawn Stacey, PhD, LMHC, is a published author, college professor, and mental health consultant with over 15 years of counseling experience.