Hypoglycemia is the condition when your blood glucose (sugar) levels are too low. It happens to people with diabetes when they have a mismatch of medicine, food, and/or exercise. Non-diabetic hypoglycemia, a rare condition, is low blood glucose in people who do not have diabetes.
http://www.hormone.org/questions-and-answers/2013/nondiabetic-hypoglycemia
If your blood sugar drops too low, you can have a low blood sugar reaction, called hypoglycemia. A low blood sugar reaction can come on fast. It is caused by taking too much insulin, missing a meal, delaying a meal, exercising too much, or drinking too much alcohol.
http://www.webmd.com/diabetes/blood-sugar-levels
That is why it is very important to test your blood and keep taking your medicine (insulin or diabetes pills) when you have an infection or are sick. Your blood sugar may be too high if you are very thirsty and tired, have blurry vision, are losing weight fast, and have to go to the bathroom often.
http://www.webmd.com/diabetes/blood-sugar-levels
Hypoglycemia is more likely to occur when you start taking a new medication (it can take practice to match your food intake to your insulin dose, for example) or if you exercise more than usual. As blood sugar drops to low levels, you may feel:  Shaky.
http://www.health.com/health/condition-article/0%2C%2C20188570%2C00.html
Although type 2 diabetes is characterized by blood sugar that is too high, some people take insulin and others medications (such as sulfonylureas) that can occasionally drive blood sugar too low. When blood sugar is too lowgenerally less than 70 mg/dLit's called hypoglycemia, and it can become a medical emergency. (The normal range for fasting blood sugar is 70 to 99 mg/dL, though it varies somewhat with age, and is lower during pregnancy and in children.). You can lose consciousness.
http://www.health.com/health/condition-article/0%2C%2C20188570%2C00.html
You'll need to test your blood sugar to confirm that you're having hypoglycemiasome people become irritable if blood sugar is too high, so it's not always obvious.
http://www.health.com/health/condition-article/0%2C%2C20188570%2C00.html
If your blood sugar stays over 240, it is too high. High blood sugar usually comes on slowly. It happens when you don't have enough insulin in your body. High blood sugar can happen if you miss taking your diabetes medicine, eat too much, or don't get enough exercise. Sometimes, medicines you take for other problems may cause high blood sugar. Be sure to tell your doctor about other medicines you take.
http://www.webmd.com/diabetes/blood-sugar-levels
Always carry rapid-acting carbohydrate with you, such as glucose tablets, a carton of fruit juice (one that contains sugar), or some sweets in case you feel symptoms coming on or your blood glucose level is low.
http://www.nhs.uk/Conditions/Hypoglycaemia/Pages/Introduction.aspx
The drink raises your blood glucose, causing your body to make more insulin. Then your blood glucose level is checked a number of times over the next five hours. Both tests check to see if your blood glucose levels drop too low.
http://www.hormone.org/questions-and-answers/2013/nondiabetic-hypoglycemia
You can have symptoms of hypoglycemia, but unless your blood glucose level is actually low when you have symptoms, you don’t have hypoglycemia. Glucose is the main source of energy for your body and brain. It comes from what we eat and drink.
http://www.hormone.org/questions-and-answers/2013/nondiabetic-hypoglycemia
what happens when your blood sugar is low
Hypoglycemia occurs when your blood sugar is low. Hypoglycemia happens when your blood sugar is low.