What is hCG? (hCG Hormone & Pregnancy Guide for Women)

hCG levels play a vital role in early pregnancy, but understanding what they mean can sometimes be overwhelming. Why do healthcare providers monitor them so closely? And what can high or low hCG levels actually indicate? For individuals who are pregnant or trying to conceive, understanding hCG is more than just interpreting numbers – it’s about gaining insight into what’s happening within your body. In this article, you’ll find a clear and complete guide to hCG levels in pregnancy – what’s considered normal, what may raise concern, and when it might be time to consult your care team.

What Is hCG?

Human chorionic gonadotropin (hCG) is a hormone that plays a crucial role in early pregnancy.

As its name suggests, it's produced by the chorion – a part of the developing placenta – and acts as a gonadotropin, meaning it helps stimulate the ovaries to maintain the pregnancy in its earliest stages.

“Maintaining the pregnancy,” in this case, means maintaining the uterine lining and halting menstruation. This creates just the right environment for the developing embryo! For this reason, hCG is often referred to as the “pregnancy hormone.”

hCG is detected both in blood and urine, and pregnancy tests are specifically designed to measure its presence. These tests, whether done at home or a healthcare provider’s office, are about 97-99% accurate when used correctly. Blood tests can detect lower levels of hCG, making them useful for early pregnancy detection and can also measure the exact amount of hCG.

hCG levels are very important as they can help assess fetal age, monitor pregnancy health, and detect conditions like ectopic pregnancy or molar pregnancy. They can also be used to check for certain birth defects in the fetus and health issues in parents unrelated to pregnancy, such as ovarian or testicular cancer.

With the Mira App, Mira Hormone Monitor, and a range of specialized Wands, you can track key fertility hormones at home and pinpoint the best time to test for hCG. Mira's lab-grade, numeric hormone readings help you detect ovulation, confirm it, and plan pregnancy with confidence – no more guesswork, just clear insights into your body.

hCG and Pregnancy Confirmation

hCG can be detected in blood as early as 6 to 12 days after ovulation, when implantation occurs. After that, hCG levels usually double every 1.4 to 2.1 days.

Highly sensitive blood tests can pick up even tiny amounts of hCG, making them the earliest way to confirm pregnancy.

Urine tests, on the other hand, require higher hCG levels – typically 20 to 50 mIU/mL – so they may not detect pregnancy as early (for instance, 2 weeks pregnant hCG levels may be undetectable). This is why a blood test might show a positive result before a urine test. For the most reliable results, urine tests work best after a missed period, with a follow-up test a week later if needed.

A false negative can happen if the test is taken too early, before hCG levels are high enough to be detected, though.

In rare cases, extremely high hCG levels can actually also interfere with test accuracy, a phenomenon known as the hook effect. This happens when hCG levels are so high (typically over 500,000 mIU/mL) that they overwhelm the test, preventing it from forming the proper antibody-hormone complex. Instead of giving a strong positive result, the test mistakenly reads as negative. This is most often seen in conditions like gestational trophoblastic disease, where abnormal tissue growth leads to excessive hCG production.

If you just can't wait and take a test early and receive a negative result, you should wait a week and test again.

hCG Levels by Week: What to Expect

hCG production begins shortly after implantation, with levels typically starting around 5–50 IU/L between weeks 3 and 4 of pregnancy. Then, hCG levels typically rise steadily, doubling every 1.4 to 2.1 days, and reach their peak – around 25,000 to 288,000 mIU/L – by the 8th to 10th week of pregnancy. After that, they gradually decline to about 3,600 to 117,000 mIU/L by week 25, where they stay relatively stable for the rest of the pregnancy.

One important thing about hCG levels is that doctors focus more on trends over time than single readings. They do so because, as mentioned earlier, exact levels can vary widely – for example, the peak can range between 25,000 and 288,000 mIU/L. As long as it’s within that, what matters more is whether the levels follow a healthy pattern, such as doubling every 1.4 to 2.1 days early on and then gradually declining after the 10th week of pregnancy. Many healthcare providers use an hCG calculator to track these patterns

What Low or High hCG Levels Mean

Low hCG Levels: Causes & When to Be Concerned

While hCG levels naturally vary from person to person, consistently low or slow-rising levels may signal that something isn’t progressing as expected and could point to an underlying issue that needs further evaluation.

• Miscalculated conception date
  
  Low hCG levels are often due to the pregnancy being earlier than initially estimated – what was believed to be 6 to 12 weeks may actually be fewer weeks along. In such cases, ultrasounds and repeat hCG testing can help determine the accurate gestational age.
  

• Ectopic pregnancy
  
  In a normal pregnancy, the β-hCG level doubles every 48-72 hours until the 8th to 10th week. In ectopic pregnancies, hCG levels usually increase less. Mean serum β-hCG levels are lower in ectopic pregnancies than in healthy pregnancies. That said, no single serum β-hCG level is diagnostic of an ectopic pregnancy, as ectopic pregnancies are usually diagnosed by carrying out a transvaginal ultrasound scan.
  

• Blighted ovum or miscarriage risk
  
  If hCG levels are not rising as expected or begin to drop, it may be a sign of a miscarriage or an early pregnancy loss such as a blighted ovum, where a fertilized egg implants but doesn’t develop into an embryo. To assess the situation, healthcare providers typically monitor hCG levels over several days to track changes and confirm whether the pregnancy is progressing.

High hCG Levels: Causes & Potential Concerns

It's also important to consider when hCG levels are higher than expected, as this may indicate that something unusual is happening and should be looked into further. Below are some of the most common reasons behind elevated hCG and what they might indicate.

Twin/multiple pregnancy

A higher hCG level can suggest the possibility of twins, as indicated by a 2018 study, but it’s not definitive on its own. As mentioned earlier, several other factors could lead to an elevated hCG reading.

To confirm whether you're carrying multiples, your doctor will need to conduct an ultrasound. The good news is that ultrasounds can detect multiples as early as 6 weeks after conception!

Molar pregnancy

High hCG levels can sometimes be linked to a molar pregnancy, a rare condition where abnormal tissue grows in the uterus instead of a healthy embryo. In complete moles, hCG levels often exceed 100,000 mIU/mL very early and may be accompanied by vaginal bleeding or an unusually large uterus.

Partial moles tend to have milder symptoms and lower hCG levels, and are often only diagnosed after further testing.

Chromosomal abnormalities

Elevated hCG levels can sometimes be associated with chromosomal abnormalities in embryos. Studies suggest that embryos with chromosomal imbalances (such as embryos with Down syndrome) may produce higher amounts of hCG compared to those with balanced chromosomes.

While this can be concerning, it's essential to remember that many factors influence hCG levels, and further diagnostic tests are necessary to fully understand the situation.

hCG Testing: Blood vs. Urine Tests

At-home pregnancy tests (urine tests) are convenient, fast, and easy to use, but blood tests (serum hCG tests) are more accurate.

An hCG test for pregnancy performed in a clinical setting can detect pregnancy earlier, as blood tests can measure lower levels of hCG (as low as 1–2 mIU/mL), while most urine tests only detect levels above 20 mIU/mL

Additionally, blood tests are less likely to give false results and can provide exact hCG levels, which are useful for monitoring early pregnancy or potential complications.

Qualitative hCG tests (like most at-home urine tests) simply tell you if hCG is present – so you get a "yes" or "no" answer to whether you're pregnant.

Quantitative hCG tests (blood tests), on the other hand, measure the exact amount of hCG in the blood. These are used to track early pregnancy progression, detect potential complications (like ectopic pregnancy or miscarriage), or monitor hCG-producing tumors.

In short: qualitative = yes/no, quantitative = how much and how it's changing.

For those looking to monitor their fertility more closely at home, the Mira App, Hormone Monitor, and Wands offer a smart, lab-grade alternative. Mira provides numeric hormone readings – including the estrogen metabolite E3G, LH, progesterone metabolite PdG, and FSH – so you can better understand your cycle, track ovulation, and know when to test for pregnancy.

With the right timing, Mira can help you optimize when to take an at-home test and support you with personalized hormone insights every step of the way.

hCG After Pregnancy: Postpartum & Miscarriage Recovery

hCG levels typically return to zero within 7 to 60 days after delivery.

The same happens if, unfortunately, a miscarriage happens. Your levels of hCG will continue to drop after a miscarriage. Depending on how far along the pregnancy was, they should reach baseline levels between 7 and 60 days following the miscarriage. The return to pre-pregnancy hCG levels is typically faster for women who miscarry early in pregnancy.

What’s also important to note is that, until hCG fully clears, ovulation may be delayed. This can make it harder to predict fertile windows.

hCG and Fertility Treatments

Beyond natural conception, hCG also plays a key role in assisted reproductive technologies, where it’s often used to support ovulation and monitor early pregnancy development.

For instance, Choriogonadotropin alfa is a type of gonadotropin hormone injection used as a “trigger shot” during fertility treatments such as IVF. It supports the final steps needed for ovulation in individuals facing challenges with conception. The medication is usually available in a prefilled, ready-to-inject syringe.

hCG in Men & Non-Pregnant Individuals

Although hCG is most often associated with pregnancy, it also serves important roles in the bodies of men and non-pregnant individuals, especially when it comes to hormone regulation and fertility support.

For example, in men or adolescent boys, hCG helps the production of testosterone and sperm. In adults with fertility issues, hCG hormone shots help men with low testosterone by acting like Luteinizing Hormone (LH), a hormone that tells the testes to make testosterone. This boost is key for sperm production.

In healthy men, typical hCG levels fall between 0 and 3 mIU/mL. Higher levels can be a sign of testicular cancer, as some cancer cells can start producing hCG. The higher the hCG level, the more serious the condition might be. Other cancers, such as those of the liver, lung, pancreas, and stomach, can also raise hCG.

Sometimes, hCG can appear elevated even without cancer. This can happen in men with low testosterone (a condition called hypogonadism). In these cases, the body produces more of a hormone called LH, which can interfere with hCG tests and cause a false alarm.

Conclusion

Human chorionic gonadotropin (hCG) is a vital marker throughout pregnancy, helping confirm conception and monitor fetal health. Beyond its role as the "pregnancy hormone," hCG hormone serves important functions in fertility treatments for both women and men, supports testosterone production, and helps detect certain medical conditions. This versatile hormone offers crucial insights that empower individuals to manage their reproductive health and overall well-being.

Frequently Asked Questions 

How does beta hCG grow in natural pregnancy?

hCG levels in pregnancy typically double every 1.4 to 2.1 days in early pregnancy. hCG levels by week 8-10 arrive at the highest point, then gradually decline and stabilise for the remainder of the pregnancy.

Can a beta hCG level fall and still be pregnant?

Yes, hCG levels naturally decline after reaching their peak around weeks 8-10 of pregnancy and stabilize at lower levels for the remainder of the pregnancy, which is entirely normal.

What causes low hCG levels in early pregnancy?

Low hCG levels in early pregnancy may be caused by a miscalculated conception date, an ectopic pregnancy, or potential pregnancy complications like a blighted ovum or miscarriage risk.

Can hCG levels be used to determine what month someone conceived?

While hCG levels follow general patterns, they vary widely between individuals, making them unreliable for determining exact conception dates; ultrasounds provide more accurate dating of pregnancy.

What does hCG stand for?

“HCG” stands for “human chorionic gonadotropin,” which is the hormone most commonly associated with pregnancy.

When is hCG detected?

In urine, hCG can be detected as early as 10-14 days after your estimated date of conception. In blood, hCG can always be detected in small amounts, even if you are not pregnant. If you are pregnant, an hCG blood test can confirm pregnancy as early as six days after conception.

What is an hCG test?

An hCG test is any test taken to determine your hCG levels. This can be done with an at-home urine test (which can confirm if your levels are elevated enough for pregnancy) or a blood test (which tests for your exact hCG levels).