NHS recommendations on home pregnancy tests
The NHS advises that home pregnancy tests are accurate from the first day of your missed period (or at least 21 days after unprotected sex if you do not know your cycle dates).
If you test earlier using an ultra-sensitive early detection kit and receive a negative result, the NHS recommends testing again on the day your period was due.
A positive test result on an NHS or commercial home test is almost certainly correct; false positives are extremely rare and typically only occur with certain fertility medications containing hCG.
Worked example: UK test timing
With a period due on 14 November, testing on or after 14 November yields >99% reliability under NHS guidelines.
If testing early on 10 November produces a negative result, re-testing on 14 November provides definitive confirmation.
UK test inputs
Known Date
Enter period start date or ovulation date.
CALCULATOR QUESTIONS
NHS pregnancy test timing calculator questions
What should I do if my pregnancy test is positive?
Contact your GP surgery or local NHS maternity services directly to book your initial antenatal appointment (booking appointment) with a midwife.
Can medications cause a false positive test?
Only medications that contain hCG itself (such as Pregnyl, Novarel, or Ovidrel used in fertility treatments) can cause a false positive. Antibiotics, painkillers, and birth control pills do not affect test results.