We can’t fib to the doctor about what our home glucose monitoring values have been running, now the doctor has hA1C, an average of all a patient’s sugars for the last 3 months. We used to be able to fib, because HA1c is new.
Yes, diet and exercise leads to good glycemic control and will bring the number down, as any diabetic can tell you.
As far as being the main test, it is important, and tells doctor a lot about us, but the blood glucose level is very important to the here and now. It directs how much insulin, how many pills and what kind, is the initial diagnoser of diabetes. 3 fasting blood sugars over 110, and you might get the diagnosis.
American diabetes association says keeping hA1c below 7.0 is recommended, but it is in the works to lower that number, and a doctor tends to set goals for his individual patients, 6 being popular.

a1c is very important. While yours is normal and mine is as well. I am still considered a pre-diabetic cause of all the other numbers. My fasting blood sugar was 100 I AM CONSIDERED TO HAVE AN IMPAIRED FASTING GLUCOSE. I AM ALSO INSULIN RESISTANCE. I ALSO HAVE METIBOLIC SYNDROME.

This is the average of blood sugar for a span of time, usually 3 months. A normal healthy person who is not diabetic their A1C should be about 6.0 or lower. For someone who is diabetic the goal is to have a A1C of about 7.0 or lower.

A1C is very important for diabetics. It shows an average of a person’s blood sugars over a 3 month period or so. 5.4% is great! It’s within normal range. If your number goes up above 6% you are considered diabetic. Health wise you want your number to drop, or stay the same, but not to rise above 6%.
EDITED: KatyCat is right. My doctor just changed my goal to 6% but I think the average is 7%. She’s right.

Its an average of your glucose level for about 3 mos. 5.4 is nl for non-diabetic