Syringe Medication

No.
Do you have any sort of ID that explains why you have it. For example a diabetic card?

1) Customs is a random stop only, 95%+ are not stopped, in which case this is a non-issue.

2) Customs officers are not stupid. They have travellers coming through every day with medical conditions. They know exactly what medical supplies are normal.

I have never had an issue with this in many years travel.

Will you have this in your hand luggage of checked bags? If in your hand luggage you may have issues at security at your departure airport. You don't say where you are flying from.

I don't have any type of ID per se. I am planning the get a letter from the prescribing physician as to what the medication is for, and hopefully he will be able to provide me with a copy of the prescription as well.

I am flying from the US to Paris & Paris to Biarritz.

Assuming that this is not narcotic (think morphine or fentanyl, or something like that) you shouldn't have too many problems. Why not contact the French embassy with questions about whether your particular medication is allowed to be imported?

I just did an internet search on your question and I think this is the official French webpage regarding prescription medication: http://www.douane.gouv.fr/articles/a13412-private-individuals-carrying-medicinal-products-in-france. The page is from 2017. I don't know if there have been any amendments to it. As a previous poster noted, the syringes themselves may present a TSA (or its equivalent) issue if they are in your carry on luggage. If the syringes are pre-filled and labelled like an epi-pen, it shouldn't be a problem. The official will just take it out and look and you'll be on your way (has happened to me in Hong Kong and Florence, Italy).

At the US end, there is no issue with TSA checking your prescription drugs provided they all fit in the quart size zipper close bag. Medication can be placed in a second bag. You just have to tell them the second bag contains medicine and make sure the bag is just medicine. Leaving things in original pharmacy packages as much as possible helps the process.

Their check is reasonableness. If they do look at your drugs and you have 1000 syringes or something that is just outrageous for the amount of time you are going on your trip, they may object because that amount just isn't reasonable. I have gone with 3 months of insulin (in the original boxes from the pharmacy) and no one has ever said anything.

Checks on the European end are similar. Since I go through those checks at the end of my trip, the amount of injectables I have remaining is much smaller than what I started with and the amount has never casued any alarm.

I would not put my medicines in checked luggage simply because checked luggage does sometimes get lost and I can't do without my meds.

Clexane will be OK. Just remember the sharps box.