Symptoms of high blood sugar or low blood sugar usually develop before a diabetic coma. High blood sugar (hyperglycemia) If your blood sugar level is too high, you may have: 
Increased thirst
Frequent urination
Blurred vision
Tiredness or weakness
Headache
Nausea and vomiting
Shortness of breath
Stomach pain
Fruity breath odor
A very dry mouth
 Low blood sugar (hypoglycemia) If your blood sugar is too low, you may have: 
Shakiness
Anxiety
Tiredness or drowsiness
Weakness
Sweating
Hunger
A feeling of tingling on your skin
Dizziness or lightheadedness
Headache
Difficulty speaking
Blurry vision
Confusion
Loss of consciousness
 Some people, especially those who've had diabetes for a long time, develop a condition known as hypoglycemia unawareness. That means they don't have warning symptoms that signal a drop in blood sugar. If you have any symptoms of high or low blood sugar, test your blood sugar right away. Based on the test results, follow your diabetes treatment. If you don't start to feel better quickly, or you start to feel worse, get medical care right away.