Can anyone suggest a low carb snack to eat after I've given blood - I'd love the biscuits or crisps but don't want to undo all my hard work are the nurses won't let you leave until you've eaten something - would a small pack of sunflower seeds work?
Why the lie then?
Tell them your terms first, that you will be refusing the tea and biscuits.
Then, if they want your blood, on your terms, they'll go ahead.
If they don't want your blood, on your terms, they'll refuse.