Sorry to read you have been poorly.
Thankfully, this has not been my experience since my t1 diagnosis. However, I find I feel more under the weather if my BG is high. So, yet another, reason for trying to manage this little beast.
I notice you say you had flu, this is really horrible and, I understand, harder to handle with diabetes.
Do you have the free flu jab which is available to those of us with diabetes?
I take it every year. Apart from once feeling a little low for a couple of days after my flu jab when they also gave me a pneumonia jab, I have had no ill affects. And I have not had flu since.
The jab does not provide 100% protection but it is better than not taking it at all.