If you are currently taking any prescription medicines, ask your physician whether you can take along a supply adequate for your stay abroad, as it is not possible to fill U.S. prescriptions in other countries.  If it is possible, be sure to keep your medication in its original packaging and take a copy of the prescription with you for custom officials.    Also, it would be a good idea to carry a letter from your physician indicating the names, including the generic names and the ingredient lists, of the medications and the reason for each medication, not only will the letter help you if you get asked questions upon entering the country but also if you need to see a doctor while abroad.  The medications and any documentation from your physician should be packed in your carry on luggage.

If it is not possible to take such a supply (because of limitations of your insurance or because of the shelf life of the medications), you may need to have your medications express mailed (FedEx or DHL) to you while you are away.  Since some drugs now commonly prescribed in the U.S., such as Ritalin and Adderall, are banned in some countries, it is a good idea to check with your program to make sure that you can bring your prescription medications legally into your host county.  If you suffer from allergies, be especially sure to take an adequate supply of medication.  Big cities may even have more airborne pollutants than you are used to and may trigger severe reactions.