I travelled from oz to uk recently and packed beta needles in hand luggage in a cool bag. They didn't show up on xray and i wasn't questioned until arriving in hong kong on the way home and transferring off and onto the same plane on a brief stopover. My remaining 4 needles were just in the side pocket of my bag and I was stopped even though I'd just got off the same plane.
No great event. Showed my neuro letter and that was all.