How early can I take a pregnancy test after missing my period?

When to Take a Pregnancy Test After a Missed Period

You can take a pregnancy test on the first day of your missed period, but be aware that up to 10% of pregnancies may not be detectable at this early stage; waiting one week after the missed period will detect 97-100% of pregnancies. 1

Optimal Timing for Pregnancy Testing

First Day of Missed Period

• Most modern urine pregnancy tests (with sensitivity of 20-25 mIU/mL) can detect approximately 90% of pregnancies on the first day of the missed period 1
• The 10% of pregnancies that remain undetectable at this point are due to late implantation—some embryos simply haven't implanted yet, even though your period is "late" 1
• By the time of the expected period, 98% of pregnancies will test positive with current test kits 2

One Week After Missed Period

• Waiting 7 days after the missed period increases detection to 97-99% of pregnancies 1
• A negative test one week after the missed period virtually guarantees you are not pregnant 2
• Some studies indicate that an additional 11 days past the expected menses may be needed to detect 100% of pregnancies using standard qualitative tests 3

Understanding Why Timing Matters

The Biology Behind Test Accuracy

• Human chorionic gonadotropin (hCG) from the implanting embryo first appears in maternal blood 6-8 days after fertilization 2
• Implantation timing varies naturally—10% of clinical pregnancies have not yet implanted by the first day of the missed period 1
• During an average 28-day cycle, ovulation generally occurs during days 9-20, meaning conception timing can vary widely 3

Test Sensitivity Variations

• Most FDA-approved qualitative pregnancy tests have a sensitivity of 20-25 mIU/mL 3
• However, 60% of home pregnancy tests detect hyperglycosylated hCG (the predominant form in early pregnancy urine) less effectively than regular hCG 4
• This means actual detection rates in practice may be lower than the theoretical sensitivity suggests 1, 4

Practical Recommendations

Testing Strategy

• If you need to know immediately: Test on the first day of your missed period, understanding there's a 10% chance of a false negative 1
• If you can wait for certainty: Test one week after your missed period for near-definitive results (97-99% detection) 1
• If the first test is negative but your period doesn't start: Retest after one week 2

Common Pitfalls to Avoid

• Don't assume a negative test on the first day of the missed period definitively rules out pregnancy—you may have ovulated and conceived later than expected 1
• Be aware that what seems like a "period" could actually be implantation bleeding, which is typically lighter and shorter than normal menstruation 5
• For women with irregular cycles, calculating the "missed period" date is less reliable; consider testing 2-3 weeks after unprotected intercourse instead 3

When Earlier Testing Makes Sense

• Some highly sensitive tests (with detection limits of 6.3-13 IU/L) may detect pregnancy 3-4 days after implantation, which could be before the missed period 2, 4
• However, these ultra-early tests have higher false negative rates and should be repeated if negative 4
• If you had unprotected intercourse and need emergency contraception, don't wait for a pregnancy test—emergency contraception is most effective within 5 days of intercourse 3