Glucose (See: Glucose) is a form of sugar which is also known as dextrose. It is a simple sugar (monosaccharide) that the body produces after the digestion of food. It is mainly derived from carbohydrates. It is also derived from proteins and fats and this process is called gluconeogenesis (See: Gluconeogenesis). This happens only when the body undergoes starvation. Blood glucose is the amount of glucose present in the blood. The levels of glucose in blood depends upon the amount of food and fluids consumed and the amount secreted from liver. Glucose is present in the blood as blood carries glucose (a primary source of energy) to each and every cell of the body. Blood glucose levels are never constant even in non-diabetic people. They constantly fluctuate depending upon the activity levels, consumption of food or fluids, wakeful or sleep stages, stress and relaxed stages, seasons, and many other factors. Generally, the blood glucose levels are high after consumption of food, and they are lowest before the first meal of the day. When glucose levels drop drastically, the body goes into a condition called hypoglycemia. In hypoglycemia, a person feels nervousness, confusion, headache, convulsions, and can even go into a coma. If glucose levels in the body increase, it leads to a condition called hyperglycemia. In this condition, there is excessive urination, blurred vision, fatigue, and trouble concentrating. These are symptoms of diabetes. High glucose levels for prolonged periods of time can lead to numerous complications like diabetic retinopathy, diabetic nephropathy, diabetic neuropathy, and cardiovascular diseases. In normal people, blood glucose levels range from 70 to 100 mg/dL for fasting and less than 140 mg/dL for postprandial. For people with prediabetes, the blood glucose levels range from 101 to 126 mg/dL for fasting and 140 to 200 for postprandial. For people with known diabetes, the blood glucose levels would be more than 126 mg/dL for fasting and more than 200 for postprandial.