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Human chorionic gonadotropin (hCG) is the pregnancy hormone that is produced by the placenta soon after implantation. Implantation takes place around six to twelve days after ovulation or about five days before a missed period. After the implantation, the hormone enters the bloodstream. It shows up in the blood within two to three days and in urine within three to four days of implantation. The pregnancy blood or a pregnancy serum test detects the exact amount of the hormone in the blood. The test shows positive during a missed period (1).
Once the fertilized egg attaches to the uterine wall, the hCG levels rise rapidly. The levels increase throughout the first trimester and reach a peak at around 60 to 80 days after fertilization (2). Now is when you experience early pregnancy symptoms such as sore breasts, irregular spotting, vomiting, or pelvic pain, for which you should go for a pregnancy blood test for confirmation.
hCG doubles every 48 to 72 hours in early pregnancy, and there will be no normal hCG value in the first trimester. On average, the levels double every 30.9 hours until they reach 6500 mlU/ml in the eighth week of the last menstrual period (LMP). After this, the levels increase considerably and peak between the ninth and twelfth week. The hCG levels then decrease slightly from the 12th to 16th week, after which the levels remain constant until the end of pregnancy.
| hCG Level | Doubling Time Expected |
|---|---|
| Below 1,200 mlU/ml | 48–72 hours |
| 1,200 – 6,000 mlU/ml | 72–96 hours |
| Above 6,000 mlU/ml | Over 96 hours |
More on early hCG levels
Below is the normal amount of serum hCG levels by weeks calculated from LMP(3)
| Pregnancy Week | Normal Hcg Levels |
|---|---|
| 3 weeks | 5–50 mlU/ml |
| 4 weeks | 5-426 mIU/ ml |
| 5 weeks | 18-7,340 mlU/ml |
| 6 weeks | 1,080-56,500 mlU/ml |
| 7-8 weeks | 7,650-229,000 mIU/ml |
| 9-12 weeks | 25,700-288,000 mIU/ml |
| 13-16 weeks | 13,300–254,000 mIU/ml |
| 17-24 weeks | 4,060-165,400 mIU/ml |
| 25-40 weeks | 3,640-117,000 mIU/ ml |
Note: The change in hCG levels may not be consistent for all women at the same stage of pregnancy. Consult your doctor if you are uncertain about your test results.
The hCG pregnancy test helps you determine whether or not you are pregnant. If your blood shows hCG, then you are pregnant. With the progressing pregnancy, the hCG levels will fluctuate a lot and there will be several normal levels. According to the American Pregnancy Association (APA), relying solely on a single hCG level to evaluate the health of pregnant women is not advisable. Instead, multiple tests conducted a few days apart provide a comprehensive understanding of the situation (3).
Dropping hCG levels indicate that pregnancy is not viable. It is usually associated with failed pregnancies such as chemical pregnancies or miscarriages. A slow rise in hCG levels is linked to miscarriages or ectopic pregnancies (4). A decline in hCG levels that is slower than 21% to 35% in 48 hours is abnormal and is associated with ectopic pregnancies or the presence of trophoblastic tissue (5). Also, if the hCG levels are above 6000 mlU/ml, it is not easy to detect the possibility of pregnancy. Here, a sonogram is the best option to know the pregnancy status.
hCG calculator is a tool for detecting whether or not you are pregnant and if the pregnancy is progressing normally. You can use it to calculate the hCG doubling time by using two consecutive hCG levels, the number of days past ovulation, and the time between the tests. Once you provide these values, the hCG levels calculator will automatically calculate the results.
A hCG calculator is based on how hCG levels naturally rise during pregnancy, usually doubling every 48 in the early weeks (6). Using this pattern and your test results, it estimates expected hCG levels, calculates the difference between test results, and determines the percentage increase to monitor pregnancy progress. It also creates an hCG levels chart that allows you to monitor the rise associated with low, average, and high hCG levels.
A twin pregnancy cannot be detected from hCG values. The hCG levels rise faster in case of twins, but there isn't much scientific data on this. However, more than one fetus could have various reasons.
Doubling time refers to the time it takes for the hCG levels to increase after the embryo implants in the uterus. Doubling time is important because an increasing hCG levels are a sign of healthy pregnancy.
If the hCG levels are less than 1,200 mIU/ml (milli-International Unit/milliliter), they can double in 48-72 hours. And if the levels are between 1,200 and 6,000 mIU/ml, they double in 72-96 hours. The hCG levels hit their peak during the initial weeks of your pregnancy, between the 8th and 11th week. However, as you move further in your pregnancy and reach the final trimester, the hCG levels in your body start to decline.
To calculate your hCG levels, you will have to enter the data from two beta hCG samples. The hcg levels calculator will check the doubling time between the two levels. You have to first enter the value of your first hCG test levels, followed by the value of the second hCG test levels. Mention the time gap between the two hCG tests. Then click on the ‘calculate’ button to get the results.
According to researchers at the University of Pennsylvania School of Medicine, if you have a successful intrauterine pregnancy, the levels of hCG will increase by about 63% within two days.
In a majority of normal pregnancies, the hCG levels double in 48-72 hours, which means that they could possibly double twice in a week. As the levels increase and your pregnancy progresses, the doubling could take 96 hours.
However, if your hCG levels are increasing at a lower rate, do not panic. It could still be a healthy pregnancy.
There is no scientific and medical way through which you can safely and assuredly increase your hCG levels. There are some supplements available in the market but they are not regulated by the FDA. Do not try them as they could harm your pregnancy. If you are worried that your hCG levels are not in the normal range, speak to your doctor about your concerns and follow proper medical advice.
A bhCG test refers to a Beta Human Chorionic Gonadotropin test. While an hCG test is done through a urine sample, the bhCG test is performed on your blood sample. The bhCG test checks for a confirmed pregnancy and results will usually show as positive when you miss your first period. Your lab technician will take a small sample of blood from your vein to carry out the test.
Even though the hCG hormone is only associated with a positive pregnancy, it is possible that you have it in the system even when you are not pregnant. Here are some reasons why it could happen:
A biochemical pregnancy: One of the first reasons for positive hCG levels could be that you go through a biochemical pregnancy, which means that you do become pregnant, but you lose the fetus even before you realize that you are pregnant. The hCG levels take some time to leave your body, and when this happens you may still end up seeing it in your test results. Also, the results pick up the slightest amount of hCG levels.
Pituitary hCG: While the placenta produces hCG, it is also sometimes produced by the pituitary gland in your brain. The pituitary gland secretes various hormones that help to control your endocrine organ systems (such as reproductive organs, thyroid, pancreas, and more). The pituitary gland secretes three other hormones (the thyroid-stimulating, luteinizing, and follicle-stimulating hormones), which are very similar to the hCG hormone. If the pituitary gland secretes hCG, the levels will not increase as they do when pregnant.
Cancerous cells: In some cases, the hCG hormone is also produced if you have any cancerous cells in your body. Particularly some ovarian tumors are known to secrete hCG
Interference from antibodies: It is possible that you have some antibodies in your blood that interfere in your hCG test and show a false presence or a false high count. However, it will only happen when you take the blood sample test.
If your hCG levels are dropping even if you have a confirmed pregnancy, it could mean quite a few things. Firstly, it could mean you have irregular or longer menstrual cycles than most women. Secondly, a drop in the levels of hCG could mean that you may have an ectopic pregnancy or a miscarriage (7).
A study was conducted in which a pregnant woman had dropped levels of the hCG hormone, and even though her physician felt it was a case of miscarriage or a non-viable pregnancy, later tests revealed that she could go ahead with the pregnancy (10).
Most home pregnancy test kits detect and measure hCG levels in the urine, but don't display the exact hCG levels. Unless you are using a digital pregnancy test kit, which records the exact hCG levels in your urine, you cannot determine the hCG amounts through a pregnancy test at home.
Disclaimer: One of your first brushes with hCG will be when you take a home pregnancy test or get a blood test done to determine whether or not you are pregnant. Whatever your results, make sure you run them by your doctor to know exactly what's happening. It's possible that the hCG levels may sometimes also show a false reading, it is best to get it checked through your medical care professional.
Moms, did you take a urine test or blood test to check your pregnancy status? Did the results come out accurate or were you confused?
References:
[1] T Chard; Pregnancy tests: a review; Human reproduction (1992). https://pubmed.ncbi.nlm.nih.gov/1639991/
[2] Gerald Konrad; First-trimester bleeding with falling HCG; Canada Family Physician (2007). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1949168/
[3] What are HCG Levels? https://americanpregnancy.org/getting-pregnant/hcg-levels/
[4] Pregnancy test. https://medlineplus.gov/ency/article/003432.htm/
[5] W Y Zhang and G L Yen; Serum SP1, hPL, and beta-hCG levels in trophoblastic diseases; Chinese Medical Journal (Engl) (1991). https://pubmed.ncbi.nlm.nih.gov/1723674/
[6] W Y Zhang and G L Yen; Serum SP1, hPL, and beta-hCG levels in trophoblastic diseases; Chinese Medical Journal (Engl) (1991). https://pubmed.ncbi.nlm.nih.gov/1723674/
[7] Demetrio Larraín and Javier Caradeux; β-Human Chorionic Gonadotropin Dynamics in Early Gestational Events: A Practical and Updated Reappraisal (2024). https://onlinelibrary.wiley.com/doi/10.1155/2024/8351132/
[8] Tim I M Korevaar et al., Reference ranges and determinants of total hCG levels during pregnancy: the Generation R Study. https://pmc.ncbi.nlm.nih.gov/articles/PMC4584104/
[9] Beata Seeber; What serial hCG can tell you, and cannot tell you, about an early pregnancy (2012). https://www.researchgate.net/publication/231859969_What_serial_hCG_can_tell_you_and_cannot_tell_you_about_an_early_pregnancy/
[10] Gerald Konrad; First-trimester bleeding with falling HCG (2007). https://pmc.ncbi.nlm.nih.gov/articles/PMC1949168/
