Our BG levels are affected by many things - food is the obvious one but there is also the time of day, year, month, stress, exercise, alcohol, illness, drugs, ...
When we are ill, our body releases extra sugar to help us fight the bugs. Unfortunately, when we have diabetes, we have less ability to convert this extra sugar to health-giving goodness. As a result, our BG levels rise when we are ill and we feel worse.
As an example, there have been times when I am poorly when my insulin needs are 40% higher than usual to keep my BG under control.
Look after yourself, monitor your BG and get well soon.