The quantitative human chorionic gonadotropin (hCG) blood test measures the level of hCG hormone present in a blood sample. HCG is a hormone that is produced during pregnancy. The hCG quantitative test is also known as quantitative serial beta hCG, repeat quantitative beta hCG, beta-hCG blood test, and quantitative blood pregnancy test.
Human chorionic gonadotropin, or hCG, is a hormone produced during pregnancy. The hormone is made by cells that form the placenta, the sac that nourishes the egg after fertilization and attaches to the uterine wall.
HCG can first be detected in a blood sample approximately 11 days after conception. Levels of hCG continue to double every 72 hours and reach their peak around eight to eleven weeks after conception. HCG levels then decline and level off, remaining steady for the rest of the pregnancy.
The hCG quantitative test is performed to:
- confirm pregnancy
- determine the age of the fetus
- diagnose abnormal pregnancies, such as ectopic pregnancy
- diagnose a potential miscarriage
- screen for Down syndrome
The hCG quantitative test measures the level of hCG hormone in a blood sample. A health 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 is 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 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
- light-headedness or fainting
- hematoma (blood accumulating under the skin)
- infection at the needle site
Normal hCG levels during pregnancy:
Levels of hCG in weeks from last menstrual period (LMP):
- Three weeks LMP: 5 to 50 mIU/ml*
- Four weeks LMP: 5 to 426 mIU /ml
- Five weeks LMP: 18 to 7,340 mIU /ml
- Six weeks LMP: 1,080 to 56,500 mIU /ml
- Seven to eight weeks LMP: 7,650 to 229,000 mIU /ml
- 9 to 12 weeks LMP: 25,700 to 288,000 mIU /ml
- 13 to 16 weeks LMP: 13,300 to 254,000 mIU /ml
- 17 to 24 weeks LMP: 4,060 to 165,400 mIU /ml
- 25 to 40 weeks LMP: 3,640 to 117,000 mIU /ml
- non-pregnant females: <5.0 mIU /ml
- postmenopausal females: <9.5 mIU /ml
*The hCG hormone is measured in milli-international units per milliliter (mIU /ml).
Lower-than-normal hCG levels could mean:
- miscalculation of pregnancy dating
- possible miscarriage or blighted ovum
- ectopic pregnancy
Higher-than-normal hCG levels could mean:
- miscalculation of pregnancy dating
- molar pregnancy
- multiple pregnancy (twins, triplets, etc.)
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.