Glucose is a monosaccharide (simple sugar) that is the basic form of energy for the body. It is made up of carbon, oxygen, and hydrogen and is essential for cellular function. Normal glucose levels should be between 80 and 150 -- depending on the time of day. Hypoglycemia occurs when glucose levels are below 80.
Symptoms of hypoglycemia include nervousness, shakiness, dizziness and sleepiness and are more likely to be present at very low glucose levels.
Blood glucose levels consistently above 126 while fasting indicate diabetes and will require further evaluation. Symptoms of Hyperglycemia occur when glucose levels rise to above 200. Symptoms include excessive thirst and hunger, blurred vision, fatigue, dry itchy skin and frequent urination.