How high could your sugar be before you go into a diabetic coma?

It depends upon: Whether you have ketoacidosis (more common in type 1 diabetes) where coma can occur with glucoses of 600 or more -- or whether you have hyperosmolar coma with severe dehydration (more common in type 2 diabetes) where coma is usually only with a glucose of around 1000 or higher. It's extremely variable, and depends more on state of dehydration. Glucose levels doesn't correlate well with coma.