hCG Doubling Time Calculator - Rise Between Two Pregnancy Blood Tests
hCG Doubling Time Calculator
How fast hCG is rising between two blood tests
Doubling Time
How many hours it takes the hCG level to double at the rate between your two tests.
Rise per 48 Hours
Results taken at any interval are converted to the 48-hour rise doctors often quote.
Falling Levels Too
If the level drops, the halving time is shown instead.
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Reading hCG Results
Human chorionic gonadotropin (hCG) is the pregnancy hormone. In early pregnancy it typically rises quickly, often doubling every two to three days while levels are low, then more slowly after about 6,000 mIU/mL. The doubling time is t × ln 2 / ln(second ÷ first). Example: 250 rising to 520 over 48 hours is a 108% rise, a doubling time of 45.4 hours.
There is a wide normal range. Studies of healthy pregnancies suggest a minimum 48-hour rise of about 35% when the first level is low, and slower rises are expected at higher levels. A slower rise does not by itself mean a problem, and a normal rise does not rule one out; ultrasound and your clinician's judgement matter more. Always compare results from the same laboratory.
Key Takeaways
- Same lab: Different labs can report slightly different values.
- Trend over number: The rate of change matters more than any single result.
- Talk to your clinician: Only a professional can interpret results in context.