Glucose intolerance is also known as impaired glucose intolerance or pre-diabetes. An individual with impaired glucose intolerance has serum blood glucose levels outside of the normal range, but not high enough to be diagnosed as diabetes. While many individuals do not experience symptoms with impaired glucose intolerance, some have characteristic symptoms.
Diabetes is typically diagnosed when an individual has a fasting plasma blood glucose level of 126 mg/dl or more on two fasting blood glucose tests. An individual with impaired glucose intolerance will have a fasting plasma blood glucose level between 100 and 125 mg/dl. Individuals who have impaired glucose intolerance have a greatly increased risk of developing type 2 diabetes as well as cardiovascular problems such as heart disease and stroke.
One of the main symptoms of impaired glucose intolerance is a sharp increase in thirst, a condition known as polydipsia. Polydipsia occurs when the amount of glucose in the blood inhibits the uptake of glucose from the urine. The altered make-up of the urine decreases the amount of water that the kidneys reabsorb, resulting in abnormally large amounts of fluid lost in urination. The body becomes dehydrated, and excessive thirst is triggered.
Excessive and frequent urination, or polyuria, goes hand in hand with the dehydration and thirst caused by the high glucose concentration of the urine in individuals with impaired glucose intolerance. Because high amounts of fluid are being lost in the urine, the body needs extra fluids to make up for that loss; this, in turn, increases the need to urinate frequently. Nocturia, or needing to get up during the night hours to urinate, is another facet of polyuria that characterises impaired glucose intolerance.
Individuals with impaired glucose intolerance often experience problems with blurred vision that gradually increase over time. The root of the problem lies in elevated blood glucose concentrations: high amounts of glucose in the blood can, over time, cause the lens within the eye to become distorted.
Insulin resistance is another common symptom of glucose intolerance. This condition occurs when the body produces sufficient amounts of the pancreatic hormone, insulin, but the body cells are unable to respond to the insulin levels correctly. Since insulin is essential in the metabolism of glucose, an individual with insulin resistance ends up with high levels of both insulin and glucose in the bloodstream. People with this condition often have dark patches of skin on their necks, knees, elbows, or knuckles.