An hCG level is a measurement of human chorionic gonadotropin, a hormone your body produces primarily during pregnancy. In non-pregnant women, hCG sits below 5 mIU/mL. In men, it’s typically 0 to 3 mIU/mL. During pregnancy, levels can climb from single digits to over 200,000 mIU/mL, making hCG one of the most dramatically changing hormones in the human body. It’s what pregnancy tests detect, and it’s also what doctors track to monitor how a pregnancy is progressing in the early weeks.
What hCG Does in Your Body
Once a fertilized egg implants in the uterine wall, cells in the developing placenta begin releasing hCG into your bloodstream. Its most critical early job is keeping the corpus luteum alive. The corpus luteum is a temporary structure on your ovary that produces progesterone, the hormone that maintains the uterine lining so the embryo can stay implanted. Without hCG signaling, the corpus luteum would break down, progesterone would drop, and the pregnancy would end.
Beyond that, hCG plays a surprisingly broad role. It promotes blood vessel growth in the uterus, helps the uterine muscle stay relaxed rather than contracting, supports the growth and development of fetal organs, and even suppresses parts of the immune system so the body doesn’t reject the embryo. There’s also evidence that hCG receptors exist in areas of the brain involved in nausea, which may explain why morning sickness tends to peak right when hCG levels are highest.
Normal hCG Levels by Week
hCG ranges are measured in mIU/mL (milli-international units per milliliter) and are typically referenced by weeks since your last menstrual period (LMP), not weeks since conception. The ranges are wide because every pregnancy is different. What matters more than a single number is the pattern of change over time.
- Week 3: 5 to 50 mIU/mL
- Week 4: 5 to 426 mIU/mL
- Week 5: 18 to 7,340 mIU/mL
- Week 6: 1,080 to 56,500 mIU/mL
- Weeks 7 to 8: 7,650 to 229,000 mIU/mL
- Weeks 9 to 12: 25,700 to 288,000 mIU/mL
- Weeks 13 to 16: 13,300 to 254,000 mIU/mL
- Weeks 17 to 24: 4,060 to 165,400 mIU/mL
- Weeks 25 to 40: 3,640 to 117,000 mIU/mL
Notice the pattern: hCG rises steeply through the first trimester, peaks somewhere around weeks 9 to 12, then gradually declines and levels off for the rest of pregnancy. By the second and third trimesters, the placenta itself produces enough progesterone that the corpus luteum is no longer needed, so hCG’s primary job is done.
How Fast hCG Should Rise
In a healthy early pregnancy, hCG roughly doubles every 48 hours. More precisely, the average doubling time during the first six weeks after conception (up to about 8 weeks gestational age) is 1.94 days. After that, the pace slows. Between 8 and 10 weeks gestational age, the average doubling time stretches to about 4.75 days.
This doubling pattern is one of the most useful tools for evaluating early pregnancies. Rather than focusing on whether a single hCG number is “normal,” doctors typically draw two blood samples 48 to 72 hours apart and check whether the level is rising at the expected rate. A single measurement that falls on the low end of the range isn’t necessarily a problem if the next draw shows appropriate doubling. Beyond 8 weeks gestational age, the usual doubling rules become less reliable because levels naturally start plateauing.
What Slow-Rising or Falling Levels Mean
When hCG doesn’t double as expected, it can signal a few different things. Levels that rise too slowly may indicate an ectopic pregnancy, where the embryo implants outside the uterus (usually in a fallopian tube), or a pregnancy that isn’t developing normally and may end in miscarriage. Falling hCG levels in the first trimester generally point toward a miscarriage that’s already in progress.
However, slow-rising hCG alone doesn’t confirm any diagnosis. Some healthy pregnancies simply have lower-than-average levels or slightly slower rises. Doctors typically combine hCG trends with ultrasound findings to get a clearer picture. There’s a threshold called the “discriminatory zone,” the hCG level at which a pregnancy sac should be visible on ultrasound. On a transvaginal ultrasound, that threshold is generally between 1,000 and 2,000 mIU/mL. If your hCG is above that level and no pregnancy is visible in the uterus, your provider will investigate further for an ectopic pregnancy.
What Higher-Than-Expected Levels Mean
Unusually high hCG can have several explanations, some completely benign. Carrying twins or multiples is one of the most common reasons, since more placental tissue means more hCG production. An hCG level that’s significantly above the typical range for a given week often prompts an early ultrasound to check for multiple pregnancies.
In rarer cases, very high hCG points to a molar pregnancy (also called a hydatidiform mole), a condition where abnormal placental tissue grows instead of a normal embryo. Complete molar pregnancies tend to produce markedly elevated hCG, while partial molar pregnancies may show only mildly raised levels. These require treatment because the abnormal tissue won’t develop into a viable pregnancy and can occasionally become cancerous if left untreated.
Blood Tests vs. Urine Tests
Home pregnancy tests detect hCG in urine, and most have a sensitivity threshold around 25 mIU/mL. That means they won’t turn positive until hCG climbs above that level, which is why testing too early can give a false negative. There are documented cases where a blood test detects pregnancy at levels in the 80s while the urine test still reads negative, simply because urine concentration of hCG lags behind blood levels.
A blood test for hCG comes in two forms. A qualitative test gives a simple yes-or-no answer about whether hCG is present. A quantitative test (sometimes called a beta-hCG) gives you the exact number, which is what’s used for tracking doubling times and monitoring early pregnancy. Blood tests can detect hCG at lower concentrations than urine tests, making them more reliable in very early pregnancy.
One thing worth knowing: fertility medications that contain hCG can cause a false positive on both blood and urine tests. If you’ve recently had a fertility treatment involving hCG injections, you’ll typically need to wait a specific period before testing so the medication clears your system and any positive result reflects an actual pregnancy.
hCG Outside of Pregnancy
Small amounts of hCG are produced by the pituitary gland in everyone, which is why non-pregnant women and men still have trace levels. Postmenopausal women can have slightly higher baseline levels, up to about 8 mIU/mL, because changes in pituitary signaling after menopause increase production slightly.
Outside of pregnancy, elevated hCG serves as a tumor marker for certain cancers. It’s considered an extremely sensitive marker for testicular germ cell tumors, appearing in 40 to 60% of non-seminoma types and about 30% of seminomas. Elevated hCG in these contexts is generally associated with more aggressive disease. Certain ovarian tumors and a rare post-pregnancy cancer called choriocarcinoma also produce hCG, sometimes appearing weeks to months after a delivery. In these situations, hCG levels are tracked the same way they are in pregnancy, as a number that should respond predictably to treatment.