The Foreign and Commonwealth Office is warning holidaymakers to check the rules on carrying medicines abroad to avoid falling foul of local laws.

Some commonly-prescribed medicines were “controlled drugs” in certain countries, according to the FCO.

Some cold remedies are banned in Japan while some sleeping pills require a licence in Singapore.

Travellers could risk a fine or even imprisonment if they break the rules, the FCO said.

According to a survey of 2,000 adults in the UK, only a third (33%) would seek advice on medication rules before they travel.

Nearly half the population of the UK is on prescribed medication, meaning that around 21 million people could be risking difficulties.

Medication containing pseudoephedrine – found in over-the-counter medicines like Sudafed and Vicks – is banned in Japan.

In Qatar, over-the-counter medicines such as cold and cough remedies are controlled substances and must be accompanied by a prescription.

Diazepam, Tramadol, codeine and a number of other commonly-prescribed medicines count as “controlled drugs” so the FCO is advising consumers to check the regulations in the countries they are due to visit.

Failing to comply may result in arrest, a fine or imprisonment in many countries, including Greece and the UAE.

Anyone travelling this summer should visit their GP at least four to six weeks before their holiday to check if any prescribed medication contained “controlled drugs” such as codeine, the FCO said.

Other restrictions include:

• Sleeping pills, anti-anxiety pills and strong painkillers require a licence in Singapore
• Costa Rica and China require visitors to bring a doctor’s note with their prescribed medication in Costa Rica, you should
• Only take enough medication for the length of your stay, with a doctor’s note to confirm that this is the right amount
• In Indonesia, many prescription medicines such as codeine, sleeping pills and treatments for ADHD are illegal
• Tourists should always carry a doctor’s note with any personal medicine when visiting China