This one might sound obvious, but it is very easy to forget! It is of course necessary to bring any medications you are on medically, for example, those for high blood pressure, thyroid issues, heart problems, or those related to mental health illnesses.
But also think about medications you might only need as and when, for example, paracetamol, ibuprofen, vitamins, or hay fever pills. You never know when you might need them!