Should I buy malaria tablets before I travel or when I arrive in the country?

You may have heard that malaria tablets are less expensive if you buy them in the country you are travelling to. However, malaria tablets are intended to be taken for 1 day to 3 weeks before you travel. So if you wait until you arrive in a country to obtain antimalarials you risk exposure to malaria. In addition, if you are not familiar with a country, it may be harder to distinguish genuine and legitimate malaria tablet providers from others who may try to sell faulty, out-of-date or fake medications.

How long before travelling do I need to start my malaria tablets?

This depends upon which type of malaria tablets you are using.

• Malarone (Atovaquone/proguanil) should be started 1-2 days before your trip and for 1 week after your return.

• Doxycycline should be taken for 2 days before you travel and for 4 weeks after your return.

• Lariam (Mefloquine) should be taken 3 weeks before your trip and for another 4 weeks after you have returned.

Source 

NHS > Malaria