Why don’t hypodermic needles change colour to indicate that they have been used?
We have a diabetic cat that requires a daily insulin injection and one of the things that frustrates me is if my room-mate or I accidentally leave a needle on the side after use, the other person is not sure if the needle has been used or not.
Now this could be a simple matter of, “if in doubt, throw it out” but a simple visual indication to show that the needle has been used would be much more effective.
Plus it adds an extra layer of safety to prevent accidental needle re-use, especially amongst people with memory problems.