The other thing nobody has mentioned is Claire, whether we like it or not or whatever, under the 'Equal Opportunities' legislation, we are classed as 'disabled'. (I never feel disabled except when it suits me and this is exactlt the type of situation where it would suit me!)
This means in effect that people aren't ALLOWED by the law to discriminate against us.
Comments such as your colleague made, could be classed as 'harassment' - and they aren't allowed to do that to disabled people!
Don't do anything official as yet, but hopefully the knowledge gives you a bit of confidence to stick up for yourself and retort to them - Well you just better get used to it then, same as I've had to! cos I sure ain't gonna stop doing it.
Actually I had a v good experience very early in my diabetic career to encourage me to stick up for myself.
I was admitted to hospital on diagnosis and when I was learning to do my jabs, at first they used to take me into a side room off the ward. Then one day a different nurse came right to my bed with all the paraphernalia (syringes then) so I did the deed and as I finished the lady in the next bed - who was great, we had a similar sense of humour and were always finding summat to giggle about - said she thought I was ever so brave and all that junk and then added, 'I'd die if I had to do that!' and without thinking I instantly retorted 'Well - I'd die if I didn't, Brenda!' and glared at her. (Then I burst into tears because I realised for the first time, really, it was true.)
And I've used that response a lot more than once. (without the tears though now!) It certainly shuts em up and hopefully makes em THINK.