The hormone human chorionic gonadotropin (better known as hCG) is produced during pregnancy.
It is made by cells formed in 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.
Typically, 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 85% of normal pregnancies, the hCG level will double every 48 – 72 hours.CLICK TO TWEET
- 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 5 mIU/mL is considered negative for pregnancy, and anything above 25 mIU/mL is considered positive for pregnancy.
- An hCG level between 6 and 24 mIU/mL is considered a grey area, and you’ll likely need to be retested to see if your levels rise to confirm a 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 – 2,000 mIU/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 least 2,000 mIU/mL.
- 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.