HCG Doubling Time Calculator
Calculate HCG doubling time from two blood test results and assess whether the rate is normal for early pregnancy.
Results
Visualization
How It Works
HCG (human chorionic gonadotropin) typically doubles every 48-72 hours in early pregnancy. The rate slows as pregnancy progresses and HCG peaks around weeks 8-11.
The Formula
Doubling Time = Hours × ln(2) / ln(HCG2 / HCG1)
48h Increase = (248/Doubling Time - 1) × 100%
Variables
- HCG — Human Chorionic Gonadotropin — hormone produced by the placenta
- ln — Natural logarithm — used in exponential growth calculations
Worked Example
HCG 120 to 280 in 48 hours: Doubling time = 48 × ln(2) / ln(280/120) = 39.1 hours. Normal for week 5.
Practical Tips
- A single HCG value means less than the trend between two or more values.
- Doubling time naturally slows as HCG rises above 1,200 mIU/mL.
- HCG peaks at 50,000-200,000 around weeks 8-11, then declines.
- Very high HCG may indicate twins or a molar pregnancy.
- Declining HCG in early pregnancy may indicate miscarriage or ectopic pregnancy.