Hello Jan,
my daughter had the same problem and I asked the same question at a German diabetes forum. Some people gave me good advice. The high bloodsugar is caused by adrenalin. So if you are nervous because of a test the bloodsugar goes up. When the test is done and you relax the bloodsugar goes back to normal.
One mother told me how her son treats it:
1. Control the bloodsugar before the test
2. If the bloodsugar level is high (and he didn´t do any mistakes with his diabetes management) and he wants to correct he corrects only with the half insulin correction.
3. During the test he does the test and don´t remind the bloodsugar level.
4. After the test he´s testing his bloodsugar again and if he is low he eats something. If he is still high he corrects again with the half correction.
So he didn´t get any hypos again.
Maybe this helps you.