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In medicine, blood sugar is glucose in the blood. Blood sugar concentration is an important factor in diabetes.
It is also known as serum glucose level. It is expressed as millimoles per litre (mmol/l).
Normally, blood glucose levels stay within narrow limits throughout the day: 4 to 8mmol/l. But they are higher after meals and usually lowest in the morning.
In diabetes the blood sugar level moves outside these limits until treated. Even with good control of diabetes, the blood sugar level will still at times drift outside this normal range.
Regulation
Blood sugar levels are regulated by negative feedback in order to keep the body in homeostasis. The levels of glucose in the blood are monitored by the pancreas, when the concentration of glucose falls, perhaps due to exercise, the pancreas releases more glucagon. Glucagon is a hormone which targets cells in the liver, causing them to convert glycogen into glucose, increasing blood sugar levels.
If the pancreas detects an increase in blood sugar, which could be a result of eating, then it secretes more insulin. This hormone causes the liver to convert more glucose into glycogen and so decreases blood sugar levels. Diabetes mellitus type 1 is caused by insufficient or non-existent production of insulin, while type 2 is due to inadequate response to endogenous insulin (a state termed "insulin resistance", both of which result in too much glucose in the blood. Type 1 diabetes is treated by replacing the absent insulin by injection of exogenous insulin. Type 2 diabetes is treated with sulfonylureas and metiglinides, which increase pancreatic secretion of insulin; metformin, which reduces hepatic synthesis of glucose (gluconeogenesis); and thiazolidinediones (aka "glitazones"), which increase cellular sensitivity to circulating insulin. In late stage type 2 diabetes, exogenous insulin may also be required.
Why control blood sugar levels?
For reasons that are not well understood, when very high levels of blood glucose are present for years, it leads to damage of the small blood vessels.
This in turn increases your risk of developing late-stage diabetes complications such as:
Cardiovascular diseases, such as heart attacks, hypertension, heart failure, strokes and problems caused by poor circulation, eg gangrene in the worst cases.
With Type 1 diabetes, these complications may start to appear 10 to 15 years after diagnosis.
It's often less than 10 years after diagnosis of Type 2 diabetes, because this type of diabetes is often present for years before it is recognised.
By keeping the blood sugar level stable, you significantly reduce your risk of these complications.
Daily variations
A drop in blood sugar may make one feel drowsy - this typically happens after a lunch rich in starchy food. Eating a lighter or more balanced lunch may help.
To do:
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