There will be a lot of posts about what people do. That’s interesting. But the answer should begin with what is required by the law of the country that you are visiting. For that you will need to do some research. Also keep in mind, and there have been some well reported situations of this in the UK, that there are substances common in the US that are not allowed into some countries. Some countries publish lists. Again, research.
Then you might want to understand the difference between the US and some European countries on the subject of packaging and prescriptions. I am not going to presume my situation here in Hungary is typical of Europe as a whole but maybe my description will shape your decisions and make you be a little extra cautious.
To start with, here you must have the medicine in the original packaging and you must have a letter from the doctor attesting to the fact that he has prescribed the medicine for you.
In the US the prescription is called into the pharmacy, and you receive an unsealed bottle with the prescription on the bottle label. It has your name, the doctor’s name and phone number and it identifies what is in the bottle. So we assume that works for any country (original packaging and prescription). The problem is that there is no proof that what is on the label is what is in the unsealed bottle.
Here packaging will be bubble packs inside boxes. The boxes and the bubble packs are well identified as to their contents. No more guessing if what is in the bottle is what is on the label. So how will an inspector in Albania react to an open unsealed bottle full of random pills, even if the prescription is on the outside of the bottle? No idea. But it doesn’t rise to the same level of security implied by the requirements in the context of European packaging.
Then in my country they require a letter from the doctor saying he prescribed that box of bubble pack of pills to you. Why a letter? Because here the prescription is taken to a pharmacy and the pharmacist retains the prescription. You never see it again. You just walk out with a box full of bubble packs of pills. No proof of the prescription. I will make a photo copy of the prescription before I go to the pharmacy, and I am hoping that will suffice for the letter from the doctor. But don’t know.
So the Albanian inspector is expecting boxes bubble packs with the medicine name on them which ensures that the medicine in the box is as described; and a letter supporting your use of the medication. That letter will have a few official stamps on it to make it legal.
But you are showing up with an unsealed bottle with a label on it and you think you are following the rules. That’s already a flag potentially. But then many here take those pills out of the bottle and put them in baggies and carry a copy of the prescription. Now where is the paper trail? A bag full of little white pills, nothing close to original packaging and the Albanian inspector has to take your word that the prescription in your right hand which has no official stamps on it, matches the pills in your left hand.
With American prescriptions you can never meet the intent of the law in my country. So, I would say the best course of action is to get as absolutly close to the intent of the law as possible. That means original bottles and a printed prescription … better if signed by the doctor … but no one will do that.
The next question is what are the odds you will be checked? Again, do some google about a woman being checked in the UK at the airport. They confiscated her meds because they were on a restricted list ... but common in the US. How did they know? Well they checked all of her meds at customs.