Hi mumnpops
Sorry to hear you have been unwell

- hope you're on the mend.
My understanding of why blood glucose levels rise during illness/infection is as follows:
Illness/ Infection causes stress on our bodies.
When this occurs, the body needs more energy to "fight" this stressor i.e. the illness/infection which could be caused by a virus or a bacteria - the stressor could also be something like undergoing a surgical operation, dealing with a bereavement, being made redundant, moving house etc etc.
And the fact that we feel "ugh"

during illness is a stressor in itself! :roll:
The body releases hormones - called "counter-regulatory hormones" which include glucagon, epinephrine (also known as adrenaline), cortisol, and growth hormone.
These hormones then tell the liver to release extra glucose to provide the body with this energy to fight the stressor.
These hormones also unfortunately inhibit the effectiveness of insulin whether its insulin being produced by our own bodies or insulin injected - this means the body becomes somewhat more insulin resistant & the cells that normally uptake the insulin become temporarily less sensitive.
As a result, blood glucose rises & overall levels become more erratic.
Depending on the extent of the illness, blood glucose might be more difficult to control for a while after the illness.
It is also very common in diabetes, regardless of what type of diabetes it is, for a period of up to 2 weeks following illness for blood glucose levels to continue to be slightly higher and somewhat erratic before settling down again.
Hope that sort of answers the question in an understandable format!
Best wishes
Txx