That is LOW blood sugar, NOT high blood sugar. Yes, death by low blood sugar MIGHT be painless, BUT it might be terrifying as well. People HAVE DIED IN JAIL from LOW blood sugar, not because they were drunk. Most police officers cannot tell the difference. Dying from high blood sugar and diabetic ketoacidosis is not pleasant, and it may not be pleasant or quick.
Type 1 diabetic for 64 years and counting.