Thank you for the reply.
A supermarket or any other organisation for that matter pub, shop, sports ground, whatever is entitled to allow whosoever they like into the premises provided they are not excluding you on the grounds of any protected characteristic such as race, sex, religion et cetera.
They don’t actually legally have to have a reason.
In this particular case, they suspect that you committed the theft.
Whilst your medication may explain why, it is only mitigation and not a defence.
Because of the nature of what this is, it’s most unlikely they are going to refer the matter to the police although they could do. It’s also unlikely that even if the police were called, they would prosecute because this would normally be dealt with by fixed penalty.
I will give you my suggestion and that is to write to the head office a nice appealing letter (not a complaint) saying exactly what’s happened, what the store have said, and asking them to overturn the decision. At this stage you are going to get further appealing rather than complaining.
If you could please rate my service five stars (even if it’s not the answer you wanted) that would be really helpful. If you have any further questions you want to ask on this subject, I am happy to deal with those for you.