high blood sugar
Meaning of high blood sugar: More glucose circulating than the body can move into its cells, a state with several causes besides diabetes.
Definition of high blood sugar
High blood sugar means the level of glucose in the blood is above the normal range. Glucose is the body's main fuel, and insulin is the hormone that moves it out of the bloodstream and into cells. When there is too little insulin, or when cells respond poorly to the insulin present, glucose accumulates in the blood instead of being used.
What causes it?
| Cause | What happens |
|---|---|
| Type 1 diabetes | The pancreas makes little or no insulin |
| Type 2 diabetes | Cells respond poorly to insulin, and production eventually falls behind |
| Steroid treatment | Steroids raise glucose production by the liver and reduce its uptake by muscle |
| Acute illness, injury or surgery | Stress hormones push glucose up, sometimes in people without diabetes |
| Pancreatic disease | Inflammation, surgery or cancer destroys insulin-producing tissue |
| Hormone disorders | Excess cortisol or growth hormone opposes the action of insulin |
What does it feel like?
Mild elevations usually cause nothing at all and are found on a blood test. As the level climbs, glucose spills into the urine and drags water with it, so urination becomes frequent and thirst follows. Tiredness, blurred vision, weight loss despite a normal appetite, slow healing of cuts, and repeated skin or genital yeast infections are the other common signs. The blurring comes from fluid shifting inside the lens of the eye and settles once the level is controlled.
What happens when it becomes severe?
Two emergencies arise from the same problem by different routes. In diabetic ketoacidosis, seen mainly in type 1 diabetes, so little insulin is present that the body burns fat for fuel and floods the blood with acids, producing vomiting, deep rapid breathing, a sweet smell on the breath and confusion. In the hyperosmolar state, seen mainly in type 2 diabetes, glucose climbs extraordinarily high without those acids and drags out so much water that severe dehydration and drowsiness dominate. Over years rather than hours, persistently raised blood sugar damages the small vessels of the eyes, kidneys and nerves and accelerates disease in the larger arteries. The technical name for the state is hyperglycemia.
How is it measured?
A finger-prick meter or a sensor worn on the arm gives the level at that moment. A laboratory glucose test does the same from a vein, with the result depending on whether food has been eaten. A separate test, glycated hemoglobin, reports an average over the preceding weeks by measuring how much glucose has become stuck to the red cell pigment, which is why it is used to judge control rather than to catch a single high reading.
Also known as
Used in a sentence
High blood sugar was documented throughout the admission and settled once the infection was treated.
Good to know
A single raised glucose reading during acute illness does not by itself establish diabetes, since infection, injury, surgery and steroid treatment all push the level up temporarily.
Word origin
Where “high blood sugar” comes from
Hyperglycemia, the technical name, joins the Greek hyper, meaning above, with glykys, meaning sweet, and haima, meaning blood.