Hyperglycaemia is the medical term for a high blood sugar (glucose) level. It's a common problem for people with diabetes. It can affect people with type 1 diabetes and type 2 diabetes, as well as pregnant women with gestational diabetes. It can occasionally affect people who don't have diabetes, but usually only people who are seriously ill, such as those who have recently had a stroke or heart attack, or have a severe infection. Hyperglycaemia shouldn't be confused with hypoglycaemia, which is when a person's blood sugar level drops too low.