Blood
Sugar Levels
Blood sugar level (also known as
blood glucose level) is the amount of glucose (sugar) in the blood.
It is also known as serum glucose level. The amount of glucose in
the blood is expressed as millimoles per litre (mmol/l). Blood sugar
levels are tightly regulated in the human body. Glucose, transported
via the bloodstream, is the primary source of energy for the body's
cells.
Though it is called "blood sugar," other sugars besides
glucose are found in the blood, like fructose and galactose. However,
only glucose levels are regulated via insulin and glucagon.
Normally, blood sugar levels stay within narrow limits throughout
the day (4 to 8mmol/l). But they are higher after meals and usually
lowest in the morning. If a person has diabetes, their blood sugar
levels sometimes move outside these limits. Even with good control
of diabetes, the blood sugar level will still at times drift outside
this normal range.
How are blood sugar levels regulated by the body?
The levels of glucose in the blood are monitored by the cells in
the pancreas. If the blood glucose level falls to dangerous levels
(as in very heavy exercise or lack of food for extended periods),
the pancreas releases glucagon, a hormone whose effects on liver
cells act to increase blood glucose levels. They convert glycogen
storage into glucose. The glucose is released into the bloodstream,
increasing blood sugar levels.
When levels of blood sugar rise,
whether as a result of glycogen conversion, or from digestion of
a meal, a different hormone - insulin - is released, causing the
liver to convert more glucose into glycogen, and to force muscle
and fat tissue cells to take up glucose from the blood, thus decreasing
blood sugar levels. Insulin also provides signals to several other
body systems, and is the chief regulatory metabolic control in humans.
Why control blood sugar levels?
When very high levels of blood glucose are present for years, it
leads to damage of the small blood vessels, which increases a diabetic's
risk of developing late-stage diabetes complications like eye disease,
kidney disease, nerve disease and cardiovascular diseases, such
as heart attack, hypertension, heart failure, stroke and problems
caused by poor circulation. Keeping the blood sugar levels stable
significantly reduces the risk of these complications.
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 recognized.
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