Blood sugar level or glucose level
Your blood sugar level means nothing other than the amount of glucose in your blood. Glucose is a single carbohydrate. Like proteins and fats, carbohydrates are a nutrient that is absorbed into the body via the intestinal wall.
Insulin is a hormone and is produced by the pancreas. When glucose enters the blood, exactly enough insulin is produced to restore the blood sugar level to balance. Insulin has a key function in this process: it makes the body cells accessible for glucose where it can then be burned. This burning process creates the necessary energy for the human body.
In people with diabetes too little or no insulin is produced, as a result of which too much glucose ends up in the blood with all kinds of annoying effects.
Read more about diabetes.