When a doctor says that a woman’s hCG level is low after one quantitative hCG blood test, that usually means that the number of milli-international units (mIU) per milliliter (mL) of blood is lower than the normal range of hCG for the number of weeks since the woman’s last menstrual period.
A single low hCG result on a blood test is not enough to diagnose a miscarriage in early pregnancy, unless the low hCG level follows an earlier, higher hCG level. Usually, if a doctor believes that a single hCG result is low, the doctor will order another one in two to three days to check the hCG doubling time.
In early pregnancy, one low hCG result is not necessarily cause for concern; normal hCG levels vary dramatically from person to person. When hCG levels are rising too slowly or dropping over time, however, this could be a symptom of miscarriage or other pregnancy complications.
Sources:
American Pregnancy Association, "Human Chorionic Gonadotropin (hCG): The Pregnancy Hormone." July 2007. Accessed 17 Jan 2008.
Barnhardt, Kurt T., Mary D. Sammel, Paolo F. Rinaudo, Lan Zhou, Amy C. Hummel, and Wensheng Guo, "Symptomatic Patients With an Early Viable Intrauterine Pregnancy." Obstetrics & Gynecology 2004. Accessed 14 Jan 2008.
