Before everyone jumps on the bandwagon here I will just mention that there are some medications which come in large volumes for daily use and you wouldn't be able to take more than a couple of days supply with you in hand luggage. This means that: 1. You have to check in at least 1 item of luggage and 2. Your hand luggage may have only 2-3 days supply. There is a necessity for a degree of reliance on airline handling going well or at least reuniting you with lost luggage in a reasonable timeframe.

If anyone else finds themselves in this situation you need to call your travel insurance company, see a US physician and obtain a private prescription (at full cost) for whatever is needed. Keep all your receipts and BA will reimburse.