Human chorionic gonadotrophin (hCG) is commonly known as the pregnancy hormone. It is produced shortly after implantation and is the hormone detected by home pregnancy tests.
For many women, particularly those who have experienced a previous miscarriage, undergone fertility treatment or developed bleeding during early pregnancy, understanding their hCG levels can be an important source of reassurance.
However, there is no single hCG level that confirms whether a pregnancy is developing normally. The significance of a result depends on how far the pregnancy has developed, how hormone levels change over time and what can be seen on ultrasound.
Key points
- Human chorionic gonadotrophin is produced by cells that will eventually form part of the placenta.
- hCG can usually be detected in the blood approximately eight to ten days after ovulation, although the exact timing varies depending on implantation.
- There is a very wide range of hCG levels in normally developing pregnancies.
- During the earliest weeks of pregnancy, hCG levels usually rise substantially over a period of 48 hours.
What is hCG and why is it important?
Human chorionic gonadotrophin is produced by cells that will eventually form part of the placenta.
Its main role during early pregnancy is to support the corpus luteum, a temporary structure in the ovary that produces progesterone. Progesterone helps maintain the lining of the uterus and supports the developing pregnancy. hCG production begins shortly after implantation, usually around six to twelve days after ovulation.
As pregnancy develops, hCG levels increase rapidly during the first few weeks. They generally reach their highest levels at approximately eight to ten weeks before gradually declining and stabilising during the remainder of pregnancy.
When can hCG first be detected?
hCG can usually be detected in the blood approximately eight to ten days after ovulation, although the exact timing varies depending on implantation. Home pregnancy tests detect hCG in urine and generally become more reliable around the time of the expected menstrual period.
A blood test can measure much smaller amounts of hCG than most urine pregnancy tests. A quantitative blood test, often called a serum β-hCG test, measures the concentration of pregnancy hormone in the blood and provides a numerical result. Results are usually reported in international units per litre (IU/L), which are numerically equivalent to mIU/mL.
What are normal hCG levels during early pregnancy?
There is a very wide range of hCG levels in normally developing pregnancies. Two women at the same gestational age may have very different results, even when both pregnancies are progressing normally. The following table provides approximate ranges commonly reported during early pregnancy.
| Gestational age | Approximate hCG range (IU/L) |
|---|---|
| 3 weeks | 5–50 |
| 4 weeks | 5–426 |
| 5 weeks | 18–7,340 |
| 6 weeks | 1,080–56,500 |
| 7–8 weeks | 7,650–229,000 |
| 9–12 weeks | 25,700–288,000 |
These ranges are illustrative rather than diagnostic. They vary between laboratories, populations and methods of measuring hCG. An hCG result that appears low or high for the estimated gestational age does not necessarily indicate a problem. Pregnancy dates may also be inaccurate, particularly if ovulation occurred earlier or later than expected.
How quickly should hCG levels rise?
During the earliest weeks of pregnancy, hCG levels usually rise substantially over a period of 48 hours. It is often said that hCG should double every 48 hours. However, this is an oversimplification.
A normally developing pregnancy does not always show an exact doubling of hCG every two days. The expected rate of increase depends partly on the initial hCG concentration. Research suggests that the minimum rise over 48 hours in some viable intrauterine pregnancies may be approximately:
| Initial hCG level | Minimum rise over 48 hours | Average rise over 48 hours |
|---|---|---|
| Below 1,500 IU/L | 49% | About 124% slightly more than doubling |
| 1,500–3,000 IU/L | 40% | |
| Above 3,000 IU/L | 33% |
The average rise is based on research across all early pregnancies. The minimum rise is lower when the starting level is higher. The minimum figures describe lower limits observed in research rather than targets that every pregnancy must achieve. A slower rise may raise concern about an abnormal pregnancy, but hCG measurements alone cannot reliably diagnose miscarriage or ectopic pregnancy. Similarly, a satisfactory rise does not completely exclude an ectopic pregnancy.
Why might my clinician request two hCG blood tests?
Serial hCG testing means measuring the hormone on two or more occasions, usually approximately 48 hours apart. This is particularly useful when a pregnancy is too early to assess clearly on ultrasound or when the pregnancy’s location has not yet been confirmed.
For example, a woman may have a positive pregnancy test but no definite pregnancy visible within the uterus during an early scan. This is called a pregnancy of unknown location. In this situation, serial hCG measurements can help guide the timing of further ultrasound examinations and the need for clinical review.
The recommendation is to use the change in hCG over approximately 48 hours to help determine the next steps:
- A rise of more than 63% suggests that a developing intrauterine pregnancy is likely, although an ectopic pregnancy cannot be excluded.
- A fall of more than 50% suggests that the pregnancy is unlikely to continue.
When the change falls outside these patterns, further clinical assessment is particularly important.
Read more: Pregnancy of Unknown Location: What Happens Next?
Can hCG levels tell whether my pregnancy is developing normally?
Not reliably on their own. A single hCG result cannot confirm whether an embryo is growing normally or whether a heartbeat is present. Serial measurements may provide useful information during the earliest weeks, but there is considerable overlap between the hormone patterns seen in normally developing pregnancies, miscarriages and ectopic pregnancies.
Once an intrauterine pregnancy and embryo can be clearly assessed on ultrasound, ultrasound findings generally provide more useful information about pregnancy development than repeated hCG measurements. In particular, the size of the embryo, its growth over time and the presence of heart activity are more important than whether hCG levels continue to double.
Read more: When Can You See a Baby’s Heartbeat on an Early Pregnancy Scan?
Can hCG levels predict miscarriage?
No. A single hCG level cannot diagnose miscarriage.
A falling hCG level during early pregnancy may indicate that the pregnancy is not continuing normally. Similarly, a rise that is slower than expected may raise concern. However, neither finding should be interpreted in isolation.
The diagnosis depends on the woman’s symptoms, ultrasound findings, gestational age and, where necessary, repeat investigations. Occasionally, hCG levels may continue to rise for a period even when an embryo has stopped developing. This is one reason why pregnancy symptoms and hormone levels cannot reliably establish whether a baby has a heartbeat. Miscarriage should not be diagnosed solely from a single hCG result or an apparently abnormal rise.
Read more: Miscarriage and Early Pregnancy Loss: How Is It Diagnosed?
Can hCG levels diagnose an ectopic pregnancy?
No. hCG levels cannot reliably determine where a pregnancy is located.
An ectopic pregnancy occurs when the pregnancy implants outside the uterus, most commonly within a fallopian tube. Some ectopic pregnancies show a slower-than-expected rise in hCG, while others may demonstrate patterns that overlap with normally developing pregnancies. A falling hCG level does not completely exclude an ectopic pregnancy.
When the pregnancy’s location is unknown, clinical symptoms, ultrasound findings and serial hCG measurements must therefore be considered together. A woman with a positive pregnancy test and significant abdominal pain, dizziness, fainting or shoulder-tip pain requires urgent medical assessment regardless of her hCG level.
Read more: Ectopic Pregnancy: Symptoms, Ultrasound and Diagnosis
At what hCG level should a pregnancy be visible on ultrasound?
The likelihood of seeing a pregnancy within the uterus increases as hCG levels rise.
A pregnancy sac may occasionally be seen on a transvaginal scan when hCG is as low as about 400 IU/L. Once hCG is above about 3,500 IU/L, a pregnancy sac can be seen in almost all normally developing pregnancies within the uterus.
Visibility also depends on gestational age, the ultrasound equipment, the experience of the examiner and whether the pregnancy is singleton or multiple.
A pregnancy should not be diagnosed as ectopic or non-viable simply because no gestational sac is visible above a particular hCG level. When the scan is inconclusive, appropriate follow-up with repeat ultrasound and, where indicated, serial hCG measurements is safer than relying on a single threshold.
Read more: What Can You See on a Pregnancy Scan at 5, 6, 7 and 8 Weeks?
Are hCG levels higher in twin pregnancies?
hCG levels may be higher in twin pregnancies because there is more pregnancy-related tissue producing the hormone. However, there is considerable overlap between hCG levels in singleton and twin pregnancies. A high hCG level does not confirm that a woman is carrying twins, and a lower level does not exclude a twin pregnancy.
Ultrasound is the reliable way to establish whether a pregnancy is singleton or multiple.
Do I need regular hCG blood tests if my early pregnancy scan is normal?
In most circumstances, no.
If an ultrasound confirms an intrauterine pregnancy with an appropriately developing embryo and visible heart activity, repeated hCG measurements are not usually necessary. This is because hormone levels become less useful for assessing pregnancy development once the embryo can be evaluated directly.
In an uncomplicated pregnancy, routine antenatal care and ultrasound examinations at the recommended gestational ages are generally more informative. Additional blood tests or ultrasound examinations may be appropriate when there are symptoms, previous pregnancy complications or specific clinical concerns.
Read more: When Should I Have My First Pregnancy Scan?
When should I seek medical advice?
If you have a positive pregnancy test and experience vaginal bleeding, abdominal pain or uncertainty about your pregnancy, contact your GP, midwife or local NHS Early Pregnancy Assessment Service for advice.
Seek urgent medical assessment if you develop severe or worsening abdominal pain, significant one-sided pelvic pain, shoulder-tip pain, heavy bleeding, dizziness or fainting.
These symptoms may indicate an ectopic pregnancy or significant internal bleeding.
If you experience collapse, severe pain or heavy bleeding with faintness, call 999 or attend an Emergency Department immediately.
An hCG result should never delay urgent assessment when concerning symptoms are present.
Related pregnancy guides
Frequently asked questions
What is hCG and why is it important?
Human chorionic gonadotrophin is produced by cells that will eventually form part of the placenta.
When can hCG first be detected?
hCG can usually be detected in the blood approximately eight to ten days after ovulation, although the exact timing varies depending on implantation. Home pregnancy tests detect hCG in urine and generally become more reliable around the time of the expected menstrual period.
What are normal hCG levels during early pregnancy?
There is a very wide range of hCG levels in normally developing pregnancies. These ranges are illustrative rather than diagnostic.
How quickly should hCG levels rise?
During the earliest weeks of pregnancy, hCG levels usually rise substantially over a period of 48 hours. It is often said that hCG should double every 48 hours.
Why might my clinician request two hCG blood tests?
Serial hCG testing means measuring the hormone on two or more occasions, usually approximately 48 hours apart. This is particularly useful when a pregnancy is too early to assess clearly on ultrasound or when the pregnancy’s location has not yet been confirmed.
Can hCG levels tell whether my pregnancy is developing normally?
Not reliably on their own. A single hCG result cannot confirm whether an embryo is growing normally or whether a heartbeat is present.
Early pregnancy care at The Pregnancy Clinic
At The Pregnancy Clinic, we provide consultant-led early pregnancy ultrasound examinations and assessment when pregnancy development or location is uncertain.
Where appropriate, serum β-hCG testing may be used alongside ultrasound findings to help guide further assessment and follow-up.
Our approach is to explain the significance of your results clearly, avoid unnecessary investigations and provide individualised advice based on your pregnancy history and clinical circumstances.
Book an early pregnancy consultation → Book an early pregnancy scan →The Pregnancy Clinic is not an emergency service. If you experience severe pain, heavy bleeding, fainting or other acute symptoms, please seek urgent NHS assessment.
Clinical references
- NICE NG126 — Ectopic pregnancy and miscarriage: diagnosis and initial management
- Barnhart KT et al. Differences in serum human chorionic gonadotropin rise in early pregnancy by race and value at presentation. Obstetrics & Gynecology. 2016.
- Barnhart KT et al. Symptomatic patients with an early viable intrauterine pregnancy: hCG curves redefined. Obstetrics & Gynecology. 2004.
- Connolly A et al. Reevaluation of discriminatory and threshold levels for serum β-hCG in early pregnancy. Obstetrics & Gynecology. 2013.
- NHS — Ectopic pregnancy
- NHS — Miscarriage