I think fasting level over 5 IU is considered prediabetic. 10-30 is considered diabetic.
A hba1c of 5.4 equates to an average of 108 mg/dl (roughly 6-6.1 mmol/L) of blood sugars.
http://www.diabeteschart.org/bloodsugarchart.html
http://www.joslin.org/info/conversion_table_for_blood_glucose_monitoring.html
My A1c took an initial plummet and has stayed at 5.4 for a while. Since being pregnant my sugars have been a lot lower (70-95 mg/dl 3.9-5.3 mmol/L) so it will be interesting to see during my next lot of testing what my HbA1c will be.
Maybe working on testing fasting blood sugars and after you eat certain foods may help you to ascertain what might be keeping your sugars a bit higher. Sickness can definitely make your sugars higher.
Hba1c can also be a bit limited as well if you have red blood cells that live a bit longer as well making the count falsely higher.
Trial and error is all we can do most of the time when we are all doing this type of hacking.