A quantitative human chorionic gonadotropin (HCG) test measures the specific level of HCG in the blood. HCG is a hormone produced during pregnancy.

See also: Qualitative HCG test

Blood is drawn from a vein, usually on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

No special preparation is necessary.

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

HCG appears in the blood and urine of pregnant women as early as 10 days after conception. Quantitative HCG measurements can precisely predict the age of the fetus.

This test is also done to diagnose abnormal conditions that can raise HCG levels.

HCG levels rise rapidly during the first trimester of pregnancy and then slightly decline.

Higher-than-normal levels may indicate:

• Choriocarcinoma of the uterus
• Hydatidiform mole of the uterus
• Normal pregnancy
• More than one fetus -- for example, twins or triplets
• Ovarian cancer
• Testicular cancer (in men)

• Fetal death
• Incomplete miscarriage
• Threatened spontaneous abortion
• Ectopic pregnancy

Possible risks from any blood test include:

• Excessive bleeding
• Fainting or feeling lightheaded
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)
• Multiple punctures to locate veins

Drugs that can decrease HCG measurements include diuretics and promethazine.

Drugs that can increase HCG measurements include anticonvulsants, anti-parkinsonian drugs, phenothiazine, and promethazine.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.