An hCG test measures the level of human chorionic gonadotropin, a hormone your body produces during pregnancy. It’s the same hormone that home pregnancy tests detect, but an hCG blood test can pick up much smaller amounts and, in some cases, tell you exactly how much of the hormone is circulating. Beyond confirming pregnancy, hCG testing is used to monitor how a pregnancy is progressing, flag potential complications, and even detect certain cancers.
What hCG Does in Your Body
Human chorionic gonadotropin is made by the placenta shortly after a fertilized egg implants in the uterus. Its primary job is to signal the rest of your body that pregnancy has begun. It stops your menstrual cycle and triggers production of progesterone and estrogen, two hormones that keep the uterine lining thick and stable, support organ development in the fetus, and increase blood flow to the placenta.
In people who are not pregnant, hCG levels are normally very low. In men and postmenopausal women, a level under 5 IU/L is considered normal. Postmenopausal women can have slightly higher baseline levels, but readings above about 14 IU/L in women over 55 warrant further investigation.
Types of hCG Tests
There are three main ways to measure hCG, and each gives you different information.
A urine hCG test is what you get with a home pregnancy test. It simply tells you whether hCG is present. These tests can detect the hormone about 10 days after conception, though waiting until the first day of a missed period improves accuracy.
A qualitative blood test works the same way: it reports a positive or negative result, confirming whether hCG is in your blood. It’s slightly more sensitive than urine testing and can detect pregnancy as early as 7 to 10 days after conception.
A quantitative blood test (sometimes called a beta hCG test) measures the exact concentration of hCG in your blood. This is the version doctors order when they need to track how levels are changing over time, which makes it useful for monitoring early pregnancy health, identifying potential complications, or following up after a miscarriage or treatment for ectopic pregnancy.
When hCG Becomes Detectable
Your body starts producing hCG once implantation occurs, roughly 6 to 10 days after conception. Blood tests can pick it up within 7 to 10 days, while most urine tests need about 10 days. Testing too early is the most common reason for a false negative. If you get a negative result but your period still hasn’t arrived, retesting a few days later often gives a clearer answer because hCG levels rise rapidly in the first weeks.
Normal hCG Levels During Pregnancy
hCG levels vary enormously from person to person, so a single reading is rarely meaningful on its own. What matters more is the trend. In the first four weeks of pregnancy, hCG typically doubles every 2 to 3 days. After about six weeks, the doubling time slows to roughly every 96 hours. Levels peak somewhere between weeks 8 and 12, then gradually decline for the rest of pregnancy.
Here are general blood-level ranges by week of pregnancy:
- 4 weeks: 0 to 750 IU/L
- 5 weeks: 200 to 7,000 IU/L
- 6 weeks: 200 to 32,000 IU/L
- 7 weeks: 3,000 to 160,000 IU/L
- 8 to 12 weeks: 32,000 to 210,000 IU/L
- 13 to 16 weeks: 9,000 to 210,000 IU/L
- Second trimester (16 to 29 weeks): 1,400 to 53,000 IU/L
- Third trimester (29 to 41 weeks): 940 to 60,000 IU/L
Notice how wide those ranges are. A reading of 300 at five weeks could be perfectly healthy, and so could a reading of 5,000. That’s why doctors focus on whether levels are rising at the expected rate rather than comparing a single number to a chart.
What Doubling Time Reveals
If your initial hCG level is above baseline (over 5 IU/L), your doctor will likely order a second blood draw about 48 hours later to check whether levels are rising appropriately. A rise of at least 49% over two days, when the starting level is below 1,500 IU/L, confirms a viable pregnancy 99% of the time.
The expected rate of increase slows as levels climb higher. When the starting number is between 1,500 and 3,000 IU/L, a rise of at least 40% over 48 hours is considered normal. Above 3,000 IU/L, a 33% increase is typical. So a person further along in pregnancy with already-high levels won’t see the same dramatic jumps that someone at four weeks would.
A slower-than-expected rise, or a drop in levels, can point to either a miscarriage or an ectopic pregnancy (where the embryo implants outside the uterus). Specifically, a decline of 21% or more over 48 hours suggests a failed pregnancy, while a smaller decline raises concern for ectopic pregnancy. These patterns don’t diagnose anything on their own but tell your doctor whether imaging or further testing is needed.
hCG Testing Outside of Pregnancy
hCG isn’t exclusively a pregnancy hormone. Certain cancers produce it, which makes hCG useful as a tumor marker. Testicular cancer is the most well-known example. Cancerous cells in the testes can transform into a cell type normally found in the placenta and begin secreting hCG. Elevated levels also show up in some cancers of the liver, lung, pancreas, and stomach. In these cases, doctors use serial hCG testing to track whether treatment is working and whether the cancer returns after remission.
What Can Affect Your Results
False positives and false negatives do happen, and several factors can throw off your results.
Fertility medications that contain hCG (brand names include Pregnyl, Profasi, Novarel, and Ovidrel) will cause a positive test even if you’re not pregnant. If you’ve recently had an injection of one of these drugs, your doctor will account for the timing when interpreting results. Certain other medications can also trigger false positives on urine tests, including some antipsychotics, the anti-seizure drug carbamazepine, some anti-nausea medications, and progestin-only birth control pills.
On the other end of the spectrum, a phenomenon called the “hook effect” can cause a false negative. This happens when hCG levels are extremely high, so high that they overwhelm the antibodies in the test and paradoxically produce a low or negative reading. It’s rare, but it can occur with molar pregnancies or other conditions that drive hCG to very high concentrations. If a blood test doesn’t match clinical symptoms, labs can dilute the sample and retest to catch this error.
Marijuana use has also been associated with mildly elevated hCG levels in men, which can complicate interpretation when hCG is being used as a tumor marker for testicular cancer. In men with low testosterone, elevated levels of luteinizing hormone (a related hormone) can cross-react with the test and mimic a true hCG elevation.
What to Expect During the Test
A blood hCG test is a simple draw from a vein in your arm. No fasting or special preparation is needed. Results from a qualitative test typically come back within a few hours to a day. Quantitative results may take a bit longer depending on the lab, but most are available within 24 to 48 hours. If your doctor orders serial testing, you’ll come back for a second draw, usually two days after the first, so the two results can be compared. Urine tests, whether at home or in a clinic, give results in minutes.