Blood sugar is 178 after a small meal and half a soda. could i be diabetic?

Need fasting sugar: It is hard to interpret a post-meal glucose. That sugar is somewhat high, but you need to get a fasting glu checked, along with an a1c. If you are at risk for diabetes (overweight, family history), then you should get this checked soon.

Yes, possible : Fasting sugar 100-125 is pre-diabetes and 2-hrs after eating 140-199 is prediabetes. Fasting 126 and higher and 2 hours after eating 200 and greater is diabetes or hga1c 6.5 and greater = diabetes see md.