A qualitative HCG blood test checks if there is a hormone called human chorionic gonadotropin in your blood. HCG is a hormone produced in the body during pregnancy.

An egg is normally fertilized by a sperm cell in a fallopian tube. Within 9 days the fertilized egg moves down the fallopian tube into the uterus. It then attaches (implants) to the wall of the uterus. After the fertilized egg implants, the growing placenta starts releasing human chorionic gonadotropin (hCG) into your blood. Some hCG also gets passed in your urine. HCG can be found in the blood before the first missed menstrual period. This can be as early as 6 days after the egg implants.

HCG helps to keep your pregnancy going. It also affects the development of your baby (fetus). Levels of hCG go up fast in the first 14 to 16 weeks after your last menstrual period. They are the highest around the 14th week following your last period. They then go down gradually. The amount that hCG goes up early in pregnancy can give information about your pregnancy and the health of your baby. Soon after delivery, hCG can no longer be found in your blood.

If your blood HCG is positive and you DO NOT have a pregnancy properly implanted in the uterus, it may indicate:

- Ectopic pregnancy
- Miscarriage
- Testicular cancer (in men)
- Trophoblastic tumor
- Hydatidiform mole
- Ovarian cancer

False positive tests may occur when certain hormones are increased, such as after menopause or when taking hormone supplements.

A pregnancy test is considered to be very accurate. When the test is negative but pregnancy is still suspected, the test should be repeated in 1 week.