Hi angua!
Which type of diabetes do you have? I am assuming Type 2, no insulin. There are a couple of things that might help you. Firstly, in the absence of carbs, your body will convert about 36% of protein to glucose (according to Dr Bernstein). Personally, I find my body converts eggs very quickly. (I am LADA and take insulin - I have to use 1.5 units for a cheese omellette even though there is about 1g carb in that and normally I take insulin at 1 unit per 8-10g carb). Secondly, the milk in your tea will have an effect. I cannot tolerate milk without jabbing insulin - it has about 4.5g sugar (lactose) per 100ml so 3 cups of tea with 30ml milk per cup will have given you about 4g carb - for me, that would keep my BG up. I think many Type 2s would get away with that, but it depends how sensitive you are to carb and how much insulin you are producing and managing to use (i.e. how insulin resistant you are).
Smidge