Morning-After Pill: Why Timing Matters

Written by the Veritas Pharmacy clinical team. Address: 113 Chester Road, Sunderland. Registered with the General Pharmaceutical Council, registration number 9012617.

Emergency contraception works by delaying or preventing ovulation, and its effectiveness falls the longer you wait. Understanding the numbers helps explain why acting immediately, rather than waiting to see a familiar pharmacist or fitting it around a schedule, makes a real difference.

How effectiveness changes with time

Within 24 hours, emergency contraception is up to 95 percent effective at preventing pregnancy. Between 24 and 48 hours, effectiveness drops to approximately 85 percent. Between 48 and 72 hours, it falls further to approximately 58 percent. Beyond that window, ulipristal acetate (ellaOne) remains available up to 120 hours, with reduced but still meaningful effectiveness. The pattern is consistent: earlier is always better, and every hour of delay has a real cost.

Which pill, and why it depends on timing

Levonorgestrel (the Plan B equivalent) is most effective within 72 hours. Ulipristal acetate (ellaOne) remains effective up to 120 hours. A pharmacist advises which is most appropriate during a phone or video consultation, based on how much time has passed and individual health history — including current medications, since some, particularly certain antidepressants, can affect which option is safest.

This service does not require an in-person visit

The consultation is carried out entirely by phone or video. Where emergency contraception is clinically appropriate and delivery can reach you in time to be effective, it is dispatched for free home delivery — there is no need to travel anywhere. If delivery would not reach you quickly enough, the pharmacist advises on the fastest alternative instead, such as the nearest open pharmacy or NHS 111.

One important clarification

Emergency contraception prevents pregnancy from occurring — it does not terminate an existing pregnancy, and has no effect if you are already pregnant. If your next period is more than 5 to 7 days late, or lighter or shorter than usual, a pregnancy test is recommended, with a GP contacted if the result is positive.

Frequently asked questions about emergency contraception

Related reading: Emergency Contraception at Veritas Pharmacy · Ongoing NHS Contraception · Pharmacy First · Private pharmacist consultation · More Women’s Health articles