Blood sugar
Blood sugar concentration, refers to the amount of glucose present in the blood
of a human or animal. Normally, in mammals the blood glucose level is maintained
at a reference range between about 3.6 and 5.8 mM (mmol/l). It is tightly regulated
as a part of metabolic homeostasis.
Normal values
Fasting blood sugar=70-100 mg/dl.
Random blood sugar=100-140mg/dl.
The homeostatic mechanism which keeps the blood value of glucose in a
remarkably narrow range is composed of several interacting systems, of which
hormone regulation is the most important.
There are two types of mutually antagonistic metabolic hormones affecting blood
glucose levels:
catabolic hormones (such as glucagon, growth hormone, cortisol and
Adrenaline) which increase blood glucose;
and one anabolic hormone (insulin), which decreases blood glucose.
Blood glucose laboratory tests:
Fasting blood sugar (ie, glucose) test (FBS)
Urine glucose test
Oral glucose tolerance test (OGTT)
Glycosylated hemoglobin (HbA1C) .
Random blood Suger.( RBS)
Hyperglycemia
Hyperglycemia or high blood sugar, is a condition in which an excessive amount of glucose
circulates in the blood plasma. This is generally a glucose level higher than (200 mg/dl).
Reference ranges for blood tests are 11.1 mmol/l, but symptoms may not start to become
noticeable until even higher values such as 250–300 mg/dl or 15–20 mmol/l. A subject with a
consistent range between 100 and 126.
Signs and symptoms
Polyphagia - frequent hunger, especially pronounced hunger
Polydipsia - frequent thirst, especially excessive thirst
Polyuria - frequent urination
Blurred vision
Fatigue (sleepiness)
Weight loss
Poor wound healing (cuts, scrapes, etc.)
Dry mouth
In diabetes mellitus, hyperglycemia is usually caused by low insulin levels
(Diabetes mellitus type 1) and/or by resistance to insulin at the cellular level
(Diabetes mellitus type 2), depending on the type and state of the disease.
Low blood sugar
If blood sugar levels drop too low, a potentially fatal condition called
hypoglycemia develops. Symptoms may include lethargy, impaired mental
functioning; irritability; shaking, twitching, weakness in arm and leg muscles; pale
complexion; sweating; paranoid or aggressive mentality and loss of consciousness.
Brain damage is even possible.
Principle of glucose measurement:
Glucose is determind after enzymatic oxidation by the enzyme glucose
oxidase,the formed hydrogen peroxide reacts under the catalysis of peroxidase
withphenol and 4-aminophenazone to give the red-violet quinoneimine dye as
indicator.
GOD
Glucose + O2 + H2O Gluconic acid + H2 O 2
peroxidase
2H2 O2 + 4-aminophenazone + phenol quinoneimine + 4 H2O
Procedure:
Standard Test Reagents
10µl Serum
10 µl Standard
1ml 1ml Enzyme reagent
Mix,incubate for 5 minutes at 20-25 C or for 5 minutes at 37C.Measure the absorbance for
each tube ,read at 500 nm.
Calculation:
Absorption of sample
Concentration of serum glu = × Conc of
Absorption of Standard
Absorption of standard (mg /dl or mmol /L)
Concentration of Standard is 100mg/dl or 5.5 mmol/L.
