Prophylaxis
Treatment given to prevent something rather than to treat it.
What it means
Anything given to prevent a problem rather than to treat one that has already happened.
Common examples: malaria tablets before travel, antibiotics before an operation, blood thinners after surgery, PrEP to prevent HIV, and daily medication to prevent migraines.
The key implication is that you take it while feeling completely well, which is precisely why adherence is the main problem with all of it.
In practice
On prescriptions, travel clinic advice, and surgical discharge letters.
"Prophylactic" is the adjective, as in a prophylactic antibiotic.
Why it matters
Ask how long to continue. This is where prophylaxis most often goes wrong — malaria tablets, for instance, must continue for weeks after you return, and stopping at the airport is a recognised failure.
Ask what it does and does not protect against. No prophylaxis is complete, and knowing the residual risk matters.
Set a reminder. Taking something daily while feeling fine is genuinely hard, and it is the whole basis of whether it works.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 30, 2026