hCG Levels by Week: Why the Ranges Overlap

Beta-hCG reference ranges are so wide, and overlap so heavily between neighboring weeks, that a single result is close to uninformative on its own. Enter your week to see the published range, then read the rest of this page, which is about why that range is not a diagnostic ruler.

Why the ranges are this wide

Three separate sources of spread stack on top of each other.

The assay. More than 100 commercial hCG assays are on the market, and StatPearls notes the significant variability in reported values that follows. Your laboratory’s reference interval is the one that applies to your result, and it will not match a generic table exactly.

The dating. A reference range is indexed to gestational age, and gestational age itself is an estimate. The Generation R cohort built ranges two ways for the same 8,195 women — from ultrasound and from the last menstrual period — and found the two sets differ considerably, with the period-based ranges shifted lower.

The pregnancy. The same study found total hCG varies with maternal BMI, smoking, parity, ethnicity, fetal sex, placental weight and hyperemesis symptoms. None of that appears on a lab slip, and all of it moves the number.

The measurement that carries information is the second one

What clinicians follow is the trajectory. MedlinePlus states hCG should almost double every 48 hours at the beginning of a pregnancy. For values under 1,500 mIU/mL, StatPearls gives a firmer floor drawn from the ectopic pregnancy literature: a rise of at least 49% over 48 hours covers 99% of normally progressing pregnancies. A slower rise, or a fall of 21% or more over 48 hours, points toward a loss or an ectopic pregnancy instead.

That is why a doctor who sees an ambiguous number orders another one two days later rather than interpreting the first. Two values define a slope; one value defines nothing.

One caution about sources, since they disagree in print: the StatPearls hCG chapter describes levels doubling “approximately every 24 hours for the first 8 weeks,” which is faster than every other reference here. The 48-hour interval is the one used clinically and the one both MedlinePlus and the ectopic pregnancy literature apply.

The shape of the curve

hCG rises exponentially through the first trimester, peaks around 10 weeks, declines until about week 16, and then stays relatively flat until term. Two consequences worth knowing:

• A value falling after week 10 is the normal pattern, not a warning sign.
• A total above 100,000 mIU/mL in early pregnancy is strongly suggestive of a complete hydatidiform mole — but many normal pregnancies also reach that level at their peak, between weeks 8 and 11.

At extreme concentrations, around 500,000 mIU/mL, assays can misread through the hook effect and return a falsely negative result. It is rare, and it is the reason a result that contradicts everything else gets repeated rather than believed.

When the number is genuinely a signal

A level that plateaus before 8 weeks or fails to rise is commonly seen in a pregnancy that is not progressing, whether inside the uterus or outside it. In suspected ectopic pregnancy the discriminatory threshold — the level above which an intrauterine pregnancy should be visible on transvaginal ultrasound — has historically been set between 1,000 and 2,000 mIU/mL, and ACOG has suggested using a cutoff as high as 3,500 to avoid ending a viable pregnancy by mistake.

Which is the point: even at its most decisive, hCG works alongside ultrasound and never alone. The factors that raise the odds of an ectopic pregnancy are in ectopic pregnancy risk factors, and if you are still at the stage of confirming a pregnancy at all, see when to take a pregnancy test.

And since every range on this page is indexed to a gestational week that is itself an estimate, it is worth checking which week you are actually in: how far along would I be if I conceived.

This content is informational. Reference values vary between laboratories and pregnancies, and interpreting them is a clinician’s job.