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When to Take a Pregnancy Test
Testing too early is the single biggest reason for a negative test — even when you’re actually pregnant. Enter your last period and cycle length and we’ll tell you the earliest, most accurate, and definitive dates to take a home pregnancy test.
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How home pregnancy tests work
Home tests detect human chorionic gonadotropin (hCG) — the hormone your body produces shortly after a fertilised egg implants in the uterine lining. Levels double roughly every 48–72 hours in the first weeks, making the day of the missed period the most reliable test window.
Sensitivity and timing
- Very early tests (10 mIU/mL): may pick up hCG from about 8 days past ovulation. False negatives common.
- Standard tests (25 mIU/mL): reliable from day of expected period onwards (99% accuracy).
- Digital with conception indicator: needs higher hCG — best from 1–2 days past missed period.
Faint lines, false positives, false negatives
- Faint line = positive. Any line within the test window, no matter how faint, indicates hCG.
- False positives are very rare. Evaporation lines appear outside the test window and have no colour.
- False negatives are common when testing too early, using a diluted sample (drink less before morning test), or with a very late implantation.
When to contact your doctor
If periods are over 2 weeks late with a negative test, or bleeding is unusual (light, different colour, painful), see your GP. Less than 1% of pregnancies do not show standard hCG through home tests — a blood test confirms decisively.
Frequently asked questions
Can I test before my missed period?
Yes, but false negatives are likely. Early tests work best 3–4 days before expected period; most accurate on day of missed period.
Does first morning urine matter?
Yes in very early pregnancy — hCG is most concentrated after sleep. After the missed period it matters less.
How long do I wait to retest after a negative?
At least 2–3 days. hCG doubles every ~48 hours, so waiting improves accuracy.
Which brand is best?
Any test that shows mIU/mL sensitivity 25 or lower is reliable from day of missed period. Brand matters less than timing.
Can medications cause false positives?
Only fertility treatments containing hCG itself. Most medications — including birth control — do not cause false positives.
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Calculations based on standard obstetric formulas and WHO guidance. For medical decisions, always consult your doctor or midwife.