What should I do if I forget to take a PrEP pill?

This information presents the general principles for managing a missed or delayed dose of PrEP. Every situation is unique — if you have any doubts or concerns, contact your pharmacy for personalized advice.

Daily oral PrEP

Daily PrEP works by maintaining a constant concentration of medication in your body. A single missed dose does not immediately eliminate your protection — but the longer the delay, the lower your drug levels drop and the more your protection diminishes. The thresholds below exist for this reason: they reflect the point at which the risk becomes clinically significant.

Delay of less than 18 hours

  • Take the missed dose as soon as possible and resume your usual schedule

Delay of more than 18 hours

  • Skip the missed dose and resume your usual schedule
  • Do not double the dose — this does not restore the missed protection

Missed doses of 3 days or more over a 7-day period

  • Your protection is considered insufficient
  • Get an HIV test
  • If you have had anal or vaginal sex without a condom in the last 72 hours, contact your pharmacy to assess whether PEP is indicated

On-demand oral PrEP

On-demand PrEP requires precise timing around sex. Unlike daily PrEP, any missed or poorly timed pill can entirely compromise your protection — there is no progressive margin. If in doubt, consider that you were not protected.

The standard schedule is: 2 pills taken between 2 and 24 hours before sex, then 1 pill 24 hours after, and 1 pill 48 hours after sex.

Missing the 2 pills before sex

  • You were not protected by PrEP
  • If you had anal or vaginal sex without a condom, contact your pharmacy to assess whether PEP is indicated

Late or missed pill after sex

  • Take the pill as soon as you remember — the longer the delay, the more the effectiveness of that dose diminishes
  • If you have any doubts or concerns, contact your pharmacy

Injectable PrEP (cabotegravir)

Injectable PrEP follows a precise injection schedule. In case of a delay, a window of 7 days is generally considered the standard threshold. Beyond this date, your protection may be diminished — contact your healthcare team to manage the situation together.

Initiation phase (start of treatment)

  • Any irregularity in taking the oral pills or in the injection interval requires clinical reassessment
  • If the delay exceeds 1 day: get an HIV test and assess PEP if you have had anal or vaginal sex without a condom in the last 72 hours

Delay in the injection schedule

  • Take an oral cabotegravir tablet (Apretude) as soon as possible and continue one tablet per day until your next injection

If you have any doubts or concerns, contact your pharmacy without delay.

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