The hormone human chorionic gonadotropin (better known as hCG) is produced during
pregnancy. It is made by cells that form the placenta, which nourishes the egg after it has been fertilized and
becomes attached to the uterine wall. Levels can first be detected by a blood test about 11 days after conception
and about 12 - 14 days after conception by a urine test. In general the hCG levels will double every 72 hours. The
level will reach its peak in the first 8 - 11 weeks of pregnancy and then will decline and level off for the
remainder of the pregnancy.
Key things to remember about hCG levels:
In a bout 85% of normal pregnancies, the hCG level will double every 48 - 72
hours. As you get further along in pregnancy and the hCG level gets higher, the time it takes to double
can increase to about every 96 hours.
Caution must be used in making too much of hCG numbers. A normal pregnancy may have low hCG levels and
result in a perfectly healthy baby. The results from an ultrasound after 5 - 6 weeks gestation are much
more accurate than using hCG numbers.
An hCG level of less than 5mIU/ml is considered negative for pregnancy, and anything above 25mIU/ml is
considered positive for pregnancy.
The hCG hormone is measured in milli-international units per milliliter (mIU/ml).
A transvaginal ultrasound should be able to show at least a gestational sac once the hCG levels have
reached between 1,000 - 2,000mIU/ml. Because levels can differentiate so much and conception dating can
be wrong, a diagnosis should not be made by ultrasound findings until the hCG level has reached at
A single hCG reading is not enough information for most diagnoses. When there is a question regarding
the health of the pregnancy, multiple testings of hCG done a couple of days apart give a more accurate
assessment of the situation.
The hCG levels should not be used to date a pregnancy since these numbers can vary so widely.
There are two common types of hCG tests. A qualitative hCG test detects if hCG is present in
the blood. A quantitative hCG test (or beta hCG) measures the amount of hCG actually present
in the blood.