hCG doubling time

Two beta results in — your doubling time, 48-hour rise and a typical-range check out.

Your two beta-hCG results

hCG doubling time

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Enter both hCG results with their dates.

Change over 48 hours—
Change over 72 hours—
Time between draws—
Typical at your starting level—

Single hCG values vary enormously between perfectly healthy pregnancies — the trend between draws is what matters, and only your provider can interpret it alongside scans and symptoms. Educational tool, not medical advice.

Typical hCG levels by week of pregnancy

Weeks counted from the last menstrual period (LMP). Ranges are wide on purpose — where you fall within them matters far less than your trend.

Weeks (LMP)Typical range (mIU/mL)
35 – 50
45 – 426
518 – 7,340
61,080 – 56,500
7–87,650 – 229,000
9–1225,700 – 288,000
13–1613,300 – 254,000
17–244,060 – 165,400
25–403,640 – 117,000

Levels peak around weeks 9–12, then fall and settle for the rest of pregnancy — slowing or falling numbers late in the first trimester are the normal pattern, not a warning sign.

Related calculators

Pregnancy Due Date Pregnancy Weight Gain Ovulation Conception Period

A single hCG number tells you surprisingly little — healthy pregnancies at the same gestational age can differ by a factor of a hundred. What clinicians actually watch is the doubling time: how fast the level rises between two blood draws taken a couple of days apart. This calculator does that math for you, using the standard exponential-growth formula on your two results and the exact time between them.

Early on (below roughly 1,200 mIU/mL), hCG typically doubles every 30–72 hours. Between 1,200 and 6,000 it slows to every 72–96 hours, and above 6,000 doubling naturally stretches past four days before levels plateau and drift down after week 12. A commonly used floor for a normally progressing early pregnancy is a rise of at least ~35% over 48 hours — slower rises don't automatically mean bad news, but they do mean your provider will want to look closer, sometimes to rule out ectopic pregnancy.

If your numbers are falling, the calculator reports a halving time instead — the expected pattern after a miscarriage, a resolving ectopic, or delivery, usually tracked until levels drop under 5 mIU/mL. Whatever the direction: bring the trend to your provider. They interpret it alongside ultrasound and symptoms, which no calculator can.

Frequently asked questions

What is a normal hCG doubling time?
In early pregnancy (levels under about 1,200 mIU/mL), hCG typically doubles every 30–72 hours. From 1,200–6,000 it slows to every 72–96 hours, and above 6,000 doubling routinely takes more than four days. Slowing down as levels climb is the normal pattern, not a problem.
My hCG is rising slower than typical — is something wrong?
Not necessarily. Studies show some healthy pregnancies rise as slowly as ~35% per 48 hours at low levels. That said, a slow rise is also the classic pattern of ectopic pregnancy and early loss, which is why providers repeat draws and add an ultrasound rather than judging from two numbers alone. Share slow-rising results with your provider promptly.
What does falling hCG mean?
Falling levels mean the pregnancy hormone is being cleared — expected after a miscarriage, a resolving or treated ectopic pregnancy, or after delivery. Providers usually re-test every few days to weekly until the level drops below 5 mIU/mL, which is considered a non-pregnant level.
When does hCG stop doubling?
Doubling naturally slows through the first trimester and levels peak around weeks 9–12, then decline and plateau for the rest of pregnancy. After the peak, comparing your number to earlier draws stops being meaningful — that's normal physiology, not a red flag.
Can hCG levels tell me if it's twins?
Twins tend to produce higher hCG on average, and a very fast rise sometimes hints at multiples — but the normal ranges overlap so heavily that hCG alone can't diagnose twins. Only an ultrasound can.
Why does the same blood draw give different numbers at different labs?
Labs use different assays calibrated slightly differently, so absolute values can shift between labs. For a meaningful doubling time, both draws should come from the same lab whenever possible.

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Guides & articles

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