Hi - what might be happening, assuming that your diet and other factors haven't changed, is that your liver is making and releasing more glucose, as that is the normal response of our livers to us having an illness.
It's probable that as your glucose levels rise, your system will respond by releasing more insulin from the pancreas, to allow you to make use of the additional glucose fuel. If you had more insulin without the extra glucose, it would be more probable that your blood glucose levels would fall.
So you could have elevated levels of both glucose and insulin - easy enough to test for glucose, but more complicated to establish insulin levels.