Found this from google from someone who phoned to ask the question
I was told, when I rang up the blood donation people to ask why I couldn't donate, that it was because I had type 1 diabetes (nothing to do with being on insulin), and so there would be fewer platelets in the blood. So they would have to take more blood to get the same amount of platelets, then separate it out and recombine it to end up with whole blood with a normal number of platelets. I was told it wasnt to do with it being dangerous or harmful for me, or the resulting blood being dangerous for the recipient, just cost and time wise it wasn't worth it for them - it would cost about 3x more than blood from someone else.
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