Budd recommends asking your pharmacist for a short covering letter confirming your name, dosage and how much medicine you’re carrying. This, he said, “is often enough to avoid questions at customs, especially for controlled medicines such as codeine, tramadol or diazepam”.
Article source: https://www.huffingtonpost.co.uk/entry/medication-travel-advice_uk_6a6a0c16e4b01948ae998714