The quantitative human chorionic gonadotropin (hCG) blood test measures the level of hCG hormone present in a sample of your blood. HCG is a hormone that is produced during pregnancy. Your doctor may refer to the hCG quantitative test by another name, including:
- quantitative serial beta-hCG test
- repeat quantitative beta-hCG test
- beta-hCG blood test
- quantitative blood pregnancy test
In some cases, the hCG quantitative blood test may also be used to evaluate and manage certain types of cancer.
Cells in the placenta make human chorionic gonadotropin, or hCG. The placenta is the sac that nourishes the egg after it’s fertilized and attaches to the uterine wall.
HCG can first be detected in a blood sample about 11 days after conception. Levels of hCG continue to double every 72 hours. They reach their peak around eight to 11 weeks after conception. HCG levels then decline and level off, remaining steady for the rest of your pregnancy.
The hCG quantitative test is performed to:
- confirm pregnancy
- determine the approximate age of the fetus
- diagnose an abnormal pregnancy, such as an ectopic pregnancy
- diagnose a potential miscarriage
- screen for Down’s syndrome
In some instances, the hCG blood test is used to screen for pregnancy before a woman undergoes certain medical treatments that could potentially harm a developing baby, such as X-rays The blood test is a standard precaution that’s conducted before undergoing one of these procedures to make completely sure you’re not pregnant. This ensures that you’re protected and that the fetus isn’t harmed by the procedure.
The hCG quantitative test measures the level of hCG hormone in a blood sample. A healthcare professional takes a blood sample by following these steps:
- An elastic band is wrapped around your upper arm to stop the blood flow and to make the veins in your arm more visible so the needle can be inserted easier.
- A vein is located and the skin around the vein is cleaned with alcohol.
- The needle is inserted into the vein and a tube is attached to the end of the needle to collect the blood.
- After enough blood is collected, the elastic band is removed from your arm.
- As the needle is removed, cotton or gauze is placed onto the puncture site.
- Pressure is applied to the cotton or gauze, and it’s secured with a bandage.
While the needle is being inserted, you may feel a brief stinging or pinching sensation, or you may not feel anything at all. When the needle is in the vein, you may feel minor discomfort or stinging. Afterward, you may feel some mild throbbing at the puncture site.
After your hCG levels have been measured in the blood sample, the results are sent to your doctor who may request an appointment with you to discuss the results of the test.
There are no particular preparations required for the hCG quantitative test.
Risks involved with having blood taken are minimal. There may be a small amount of bruising where the needle was inserted, which can be minimized by applying pressure to the area for several minutes after the needle is removed.
In very rare cases, the following may occur:
- excessive bleeding
- hematoma, which happens when blood accumulates under your skin
- infection at the needle site
When your lab test comes back, your doctor will tell you what your hCG levels are. These levels are measured in milli-international units of hCG hormone per milliliter of blood (mIU/ml).
This table shows the normal hCG levels during pregnancy for each week from your last menstrual period, according to the American Pregnancy Association:
Normal hCG levels in non-pregnant women are less than 5.0 mIU/ml, and in postmenopausal women normal levels are anything less than 9.5 mIU/ml.
If your hCG levels are outside of the normal range, it could mean a variety of things. Your doctor will help you interpret the results.
Levels of hCG that are lower than normal could mean:
- a miscalculation of pregnancy dating
- a possible miscarriage or blighted ovum
- an ectopic pregnancy
Levels of hCG that are higher than normal could mean:
- a miscalculation of pregnancy dating
- a molar pregnancy
- a multiple pregnancy, such as twins or triplets
No test is 100 percent accurate every time. The hCG test can give both false-negative results and false-positive results for pregnancy. Your doctor will help you figure out your results or do follow-up testing if there’s any doubt.
If an hCG test comes back negative, that generally means that you’re not pregnant. However, if the test was performed too early in the pregnancy, before your body has had time to produce enough hCG, you can get a false negative. Because hCG levels change so quickly during early pregnancy, the hCG quantitative test should be repeated within 48 to 72 hours to observe how the hormone level is changing. Certain drugs such as diuretics, promethazine, and tranquilizers can also give false-negative test results.
On the other hand, samples that have protein, blood, or excess pituitary gonadotropin in them can cause a false-positive hCG test. It’s also possible to get a false-positive result if your body produces certain types of antibodies that have fragments of the hCG molecule. If there is any doubt about the results, a different testing method can be used to confirm.
Don’t panic if your numbers don’t exactly match the “normal” levels. These figures are estimates, and you can have hCG levels that are lower than normal and still have a healthy baby. You’ll receive an ultrasound around five to six weeks which is considered much more accurate than your hCG numbers. If there’s reason to be concerned about your pregnancy, multiple hCG readings done a couple of days apart will be used to assess your situation.
Numbers can vary, so it’s important to listen to your doctor concerning the health of your pregnancy. Your doctor will check your hCG levels if they detect a problem. Ask questions if you’re concerned about something and let them know immediately if you’re experiencing any problems.