What is hCG? Beta hCG, tests and levels

Human chorionic gonadotropin (hCG) is a hormone your body makes in early pregnancy. It is mainly made by tissue that will become the placenta after the fertilised egg has implanted in the uterus.

Laboratories usually measure the beta part of hCG, so you will often see “beta hCG” on a blood test report. This is simply the pregnancy hormone level in your blood. Beta hCG can often be detected in blood (serum, meaning in the blood) before it shows on most home urine tests. In early pregnancy, levels usually rise quickly, then the rise slows later in the first trimester. Single values can vary a lot between people and between laboratories. Watching how your level changes over time is usually more useful than looking at one number on its own, and your doctor or midwife is the best person to interpret your results in context.

Key points

• hCG is a pregnancy hormone. Laboratories usually measure the beta part, so reports often say “beta hCG”.
• The pattern over 24 to 72 hours is usually more helpful than one single value.
• Normal ranges are wide. Your timing, the laboratory method, and your overall clinical picture all matter.
• Serum (blood) tests are quantitative, which means they report a number. At-home urine pregnancy tests are qualitative, which means they usually give a yes or no result and depend on test sensitivity and how diluted your urine is.
• Trigger shots, rare antibodies, or high dose biotin supplements can affect some test results.
• Beta hCG is usually interpreted together with ultrasound findings when the pregnancy is far enough along for a scan to be useful.

How beta hCG behaves over time

After implantation, beta hCG starts to rise. In the very early weeks this rise is often quite fast, and people sometimes talk about the “doubling time” (how long it takes for the level to roughly double). Later in the first trimester the rise usually slows and the level reaches a peak before it levels off or falls slightly.

Healthy pregnancies can have different hCG patterns, which is why two or more timed blood tests are usually more helpful than one value on its own. A clear fall over time often means the pregnancy is not continuing, but there are exceptions, so your results should always be interpreted with your doctor or midwife.

Units, assays, and practical notes

Laboratories usually report beta hCG in mIU/mL or IU/L. These are standard laboratory units that let results be compared. Different laboratories may use different assays (laboratory test methods), so their numbers and reference ranges can vary slightly.

Serum (blood) tests are quantitative, which means they give a number. At-home urine pregnancy tests are qualitative, which means they tell you if hCG is detected or not and depend on the test brand and how diluted your urine is.

• Medicines: hCG trigger shots can keep blood and urine tests positive for several days. This can make it harder to tell when a pregnancy related rise has started.
• Interference: Rare antibodies in the blood and high dose biotin supplements can interfere with some assays and make results look higher or lower than they really are.
• Hook effect: Very high hCG levels can sometimes appear falsely low on certain assays. If the laboratory is concerned about this, they can usually fix it by diluting the sample and repeating the test.

Clinical uses of beta hCG

• Confirm pregnancy: Beta hCG can often be detected in blood before most home urine tests turn positive.
• Track early progression: Serial values over time help show whether levels are rising, staying flat, or falling.
• Guide ultrasound timing: Levels can help your clinician choose when an ultrasound scan is more likely to show useful information.
• Diagnose and monitor: Beta hCG is used together with ultrasound and examination when caring for ectopic pregnancy, miscarriage, and after molar pregnancy.
• Tumour marker: Certain germ cell tumours (for example, some ovarian or testicular tumours) can produce hCG in people who are not pregnant.

Our hCG calculators

Estimate gestational age from hCG levels

If you have one blood test result and want a likely week window, you can use the Weeks Pregnant from hCG calculator. It maps your value to an estimated week band and shows the reference table used. It cannot confirm that a pregnancy is healthy or rule out a problem. Ultrasound and clinical assessment are still important.

Compare your hCG results to the average

If you already know how many weeks pregnant you are, you can see where one value sits with the hCG level checker by week. For a quick reference without entering your result, you can review the hCG ranges by week lookup.

Chart your hCG trend and doubling time

If you enter two or more blood test results into the hCG trend and doubling time calculator, it estimates a line of best fit, a doubling or halving time, and a projection. If you add a dating method, it can show how your values sit relative to a typical band for that gestational age. For suspected multiples, you can also look at the twins and triplets hCG tool.

Calculate 48 hour change (two results)

If you have two blood tests only, the 48 hour hCG change calculator adjusts your interval to about 48 hours and labels the change as within typical, slow, plateau, or falling. Your clinician will still interpret the pattern in the context of your symptoms and ultrasound.

Track pregnancy test line progression

If you are logging home urine strips, the pregnancy test line progression tracker records brand, timing, and line darkness, then charts the trend. Once you start blood tests, it is usually more useful to focus on the Weeks Pregnant from hCG calculator or the hCG trend and doubling time calculator, together with your clinician’s advice.

Testing and interpretation tips

• Use the same laboratory where possible when you are tracking a trend, so the method stays consistent.
• Space blood tests by about two days when monitoring early change, unless your clinician advises a different schedule.
• Do not compare home urine strips directly to laboratory numbers. Use each type of test for its intended purpose.
• Link your results to dates, symptoms, and ultrasound planning together with your doctor or midwife.

Limits and safety note

These tools and answers are educational only. They do not diagnose, treat, or monitor any condition. Seek urgent care or call your local emergency number for severe pain, heavy bleeding, fainting, or shoulder tip pain. Always discuss any hCG results with your clinician, who can interpret beta hCG together with your history, examination, and imaging.