Pregnancy diagnostics
Understanding Serum hCG Results
Blood tests detect human chorionic gonadotropin (hCG) much earlier than urine tests. Use this tool to interpret quantitative or qualitative results and learn when to repeat testing.
Interpretation
Positive quantitative resultValues above 25 mIU/mL typically indicate pregnancy. Serial doubling every 48–72 hours supports viability.
Standardized value: 150.0 mIU/mL
How to Use This Calculator
Choose test type
Select quantitative for numeric serum results, qualitative for positive/negative thresholds.
Enter hCG value
Use the lab-reported number and unit (mIU/mL or IU/L). The calculator converts if needed.
Interpret and plan next steps
Follow guidance on retesting or prenatal follow-up based on whether the result is negative, borderline, or positive.
Formula
Qualitative thresholds (common): Negative < 5 mIU/mL, Positive ≥ 25 mIU/mL, Borderline 5–25 mIU/mL.
Conversion: 1 IU/L = 1,000 mIU/mL.
Expected doubling: In viable pregnancies, hCG typically doubles every 48–72 hours during early gestation.
Full Description
Human chorionic gonadotropin (hCG) is produced by trophoblastic tissue shortly after implantation. Quantitative serum tests detect pregnancy before missed periods, typically as early as 8–10 days post-ovulation. Interpreting hCG requires context: serial rises indicate viable intrauterine pregnancy, plateauing or falling levels suggest miscarriage or ectopic pregnancy.
Reference ranges vary widely between individuals and labs. Always correlate with ultrasound findings, last menstrual period, and clinical presentation. Abnormally high hCG may signal multiple gestation or trophoblastic disease.
hCG Levels by Gestational Age
| Gestational age | Typical range (mIU/mL) |
|---|---|
| 3–4 weeks (post-LMP) | 5 – 426 mIU/mL |
| 4–5 weeks | 19 – 7,340 mIU/mL |
| 5–6 weeks | 1,080 – 56,500 mIU/mL |
| 6–7 weeks | 7,650 – 229,000 mIU/mL |
| 7–12 weeks | 25,700 – 288,000 mIU/mL |
| 12–16 weeks | 13,300 – 254,000 mIU/mL |
| 16–29 weeks | 1,400 – 53,000 mIU/mL |
| 29–41 weeks | 940 – 60,000 mIU/mL |
Ranges are approximate. Use ultrasound for precise dating once hCG exceeds the discriminatory zone (~1,500–2,000 mIU/mL).
Frequently Asked Questions
When should I repeat a borderline result?
Repeat serum hCG in 48 hours. Rising values confirm early pregnancy; falling or flat values suggest non-viable pregnancy.
Can medications affect hCG?
Only fertility medications containing hCG cause false positives. Most drugs do not impact serum hCG readings.
What if hCG rises too slowly?
Sluggish rise may indicate ectopic pregnancy or impending miscarriage. Consult your healthcare provider promptly.
Does high hCG mean twins?
Elevated hCG can occur with multiples but is not definitive. Ultrasound confirmation is required.