I Have Been Really Terrible With My Diet Since January

I have been really terrible with my diet since January in terms of eating a lot of sweet things like cakes and chocolates continuously.

I did the HBA1c test and got 6.7% which signals diabetes.

Does it been DEFINITELY that I have diabetes or can it be that I just abused my diet.

I fasted last night and took the blood sugar test this morning and it showed 98. Then I had a green smoothie, ate oatmeal and 2 hours after it was 89.

I just had 2 slices of bread and it rose to 155 1/2 hour after I ate it. I am waiting to test later tonight to see what happens.