300mL in a medicine bottle with a suitable prescription label will get you through. You can be asked to taste it: this leads to problems, because when the dose is 5ml, and it's dangerous to exceed the dose (e.g some diuretics have side effects of leading to reduced blood pressure and you can pass out - really safe on an escalator at T5), enough to taste as a demonstration can be too much. Some medicines don't come in under 100ml sizes.
Then there's insulin. and the syringe for it, and asthma inhalers - one can go on and on. Note that walking sticks ARE allowed - apparently even by ryanair.
Belts attached to trousers can cause problems. Having lost 14kg since January, and more coming off, if my belt isn't sewn on the trousers at the back, they hang on the belt loops and become very uncomfortable.....
There's a very apt term in French to describe the situation:
'c'est un grand bordel'