Work out hCG doubling time and percentage rise between two blood tests, and compare the rise with the expected early-pregnancy pattern.
Result
How to use this tool
Use blood (quantitative beta-hCG) results in mIU/mL from the same lab.
Give the hours between the two blood draws, typically 48.
Compare the 48-hour rise with the 53% minimum.
A slow or falling pattern needs clinician review and usually ultrasound.
Formula & worked example
hCG rising from 100 to 200 mIU/mL in 48 hours doubles in 48.0 hours, a 100% rise — above the 53% minimum expected rise. A rise from 100 to 150 in 48 hours (50%) is slower than expected.
Limitations — read this before you rely on it
Pattern aid only; it cannot diagnose viable pregnancy, miscarriage or ectopic pregnancy. This tool is for education only and is not medical advice. Talk to a clinician about any result that worries you, and never change treatment because of a calculator result.
Frequently asked questions
The time for the level to double if it kept rising at the same rate: ln(2) x hours between tests / ln(second / first).
For a viable early intrauterine pregnancy, studies support a minimum rise of about 53% in 2 days; many rise much faster.
Not by itself. Slow rises occur in some viable pregnancies and in miscarriage too; diagnosis needs ultrasound and clinical assessment.
Assays and units vary, so compare results from the same laboratory and always with a clinician.
No. Single values vary widely between people; the pattern over time matters more.