I do not have any symptoms,but my fasting blood sugar is 250mg.Is the lab reading wrong?

I am asked such questions very frequently.Why the patient is not feeling anything though his blood sugar is very high?

Usually mentioned classical symptoms of Diabetes are

Frequent urination
Excessive thirst
Extreme hunger
Unusual weight loss
Increased fatigue
Irritability
Blurry vision
A patient is newly detected with a very high blood sugar[fasting blood sugar>200] but with none of the above symptoms.Why?

It happens often. If the rise in blood sugar is very slow,and if it had taken place over a period of several months,the patient may fail to notice the symptoms.Also in some patients symptoms are not there.This usually happens when many members of the family are also having Diabetes[strong family history of Diabetes].

I am more worried about a newly detected Diabetic with no symptoms because most often we wont be able to predict the duration of Diabetes. It might have started months or even years before the detection.
In those who have the above mentioned symptoms estimation of duration is easy.It will be roughly equal to duration of symptoms.