Everyday over-the-counter and prescription drugs that are widely available in the UK are subject to different regulations abroad.
In popular holiday destinations such as Greece and Dubai, failing to comply can lead to a fine or even a prison spell.
Decongestants like Sudafed and Vicks, which are used as cold remedies, are completely banned in Japan because the ingredient pseudoephedrine is illegal there.
Commonly-prescribed pills to help nervous travellers are also banned in several Asian countries.
Sleeping pills and anti-anxiety tablets currently require a licence to be brought into Singapore.
In Indonesia sleeping pills are illegal, as well as ADHD treatments and strong painkillers like codeine.
Over-the-counter drugs like common cold and cough remedies are controlled substances in Qatar so people must have prescriptions for them.
It is the same in China where tourists must always carry a doctor's note on their person.
Visitors to Costa Rica are only permitted to take enough medication for the length of their stay and there must be a doctor's note to confirm it is the right amount.
Strong painkillers like Tramadol and codeine, and anxiety pills like Diazepam, are controlled drugs in a number of countries.
It is important that people check before they set off whether the medication is allowed in the country.
If the country bans the prescription drug that you need to take daily, then you need to contact the country's foreign embassy before the trip.
In some cases the embassy may give permission to travel with the medication or they may recommend an alternative that is legal in that country.