This is not unknown and has been reported in other threads.
With diabetes, we are all different.
Some people are experiencing lower than usual blood sugars after the jab, others are experiencing higher than usual and some are experiencing no difference.
I had my first jab, expected to go higher but went lower.
As a result, I am going into my second jab with no expectations except to need to do extra testing with extra insulin on hand if I go higher than usual and extra hypo treatment on hand if I go lower.
in other words, I expect the unexpected and am grateful for the privilege of getting the added covid protection that will allow me, my friends, family, colleagues and other around me to start to return to some type of normality.