Human chorionic gonadotropin (better known as hCG) is a hormone produced during the pregnancy period. 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. The hCG levels can be detected using blood test from about 11 days after conception and by urine test from about 12-14 days after conception. Usually, 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
Studies show that in 85% of normal pregnancies, the hCG level will double every 48 – 72 hours.
When you get further along in pregnancy and if the hCG level goes higher, the time taken to double it can increase to about every 96 hours.
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 considered to be more accurate than hCG numbers.
An hCG level less than 5mIU/ml is considered to be negative for pregnancy, and anything above 25mIU/ml is considered positive for pregnancy.
Usually, hCG hormone is measured in milli-international units per milliliter (mIU/ml).
A transvaginal ultrasound will be able to show at least a gestational sac once the hCG levels have reached between 1,000 – 2,000mIU/ml. It is advised not to have a diagnosis until the hCG level has reached at least 2,000 since the levels can differentiate so much and conception dating can be wrong.
Multiple testings of hCG must be done a couple of days apart to have a more accurate assessment of the situation.
The hCG levels cannot be used to date a pregnancy since these numbers can vary so widely.
Two common types of hCG tests include; a qualitative hCG test to detect hCG in blood and a quantitative hCG test (or beta hCG) to measures the amount of hCG in the blood.
Guideline to hCG levels during pregnancy
hCG levels in weeks from LMP (gestational age) are given below:
3 weeks LMP: 5 – 50 mIU/ml
4 weeks LMP: 5 – 426 mIU/ml
5 weeks LMP: 18 – 7,340 mIU/ml
6 weeks LMP: 1,080 – 56,500 mIU/ml
7 – 8 weeks LMP: 7, 650 – 229,000 mIU/ml
9 – 12 weeks LMP: 25,700 – 288,000 mIU/ml
13 – 16 weeks LMP: 13,300 – 254,000 mIU/ml
17 – 24 weeks LMP: 4,060 – 165,400 mIU/ml
25 – 40 weeks LMP: 3,640 – 117,000 mIU/ml
What can a low hCG level mean?
In case of a low hCG level, it must be rechecked within 48-72 hours to see how the level is changing.
A low hCG level can indicate:
Miscalculation of pregnancy dating
Possible miscarriage or blighted ovum
What can a high hCG level mean?
In case of a high level of hCG also, it is required to recheck it within 48-72 hours to evaluate changes in the level.
A high hCG level can indicate:
Miscalculation of pregnancy dating
Should my hCG level be checked routinely?
The hCG levels are not checked routinely, unless you are showing signs of a potential problem. A health care provider may recheck your levels in case of bleeding, severe cramping issues, or due to history of miscarriage.
What can I expect from my hCG levels after a pregnancy loss?
The hCG level tends to return to a non-pregnant range about 4 – 6 weeks once if a pregnancy loss has occurred.
This may differ based on the reason of loss occurred (spontaneous miscarriage, D & C procedure, abortion, natural delivery) Health care providers will continue to monitor hCG levels even after a pregnancy loss in order to ensure that they return back to <5.0.
Can anything interfere with my hCG levels?
A positive test result, may indicate that you are pregnant. Even though false positives are rare, some conditions may cause a false positive, such as certain types of cancer and early miscarriage.
Medications that contain hCG and some antibodies may also interfere with hCG levels, as well.
And it is necessary to talk with your health care provider regarding the effect of medications on test.