Diabetic coma is a dread full diabetes complication that causes unconsciousness. Coma is relatively rare in diagnosed diabetes but it is important to know about the situation that increases the risk of coma. The main cause of coma occurring in people with diabetes are by low or very high blood glucose levels, Diabetic ketoacidosis is a dangerous state of having very high blood glucose levels (typically above 17 mmo/L) in combination with high ketone levels. Ketoacidosis is able to occur if the body runs out of insulin and is therefore a factor for people with type 1 diabetes to be aware of. Insulin can prevent ketone levels rising and this is the key reason why people with diabetes are advised never to miss their long term (basal) insulin injections. In type 2 diabetes, insulin levels in the body are usually present to stop ketone levels rising too high. However, at very high blood glucose levels (typically above 33 mmol/L) a dangerous condition called Hyperosmolar Hyperglycemic state (HHS) can develop.