Tahani Al-Shehri
To measure the concentration of glucose in a
serum sample for the diagnosis of diabetes
mellitus.

Fasting blood glucose :not more than 100
mg/dl
 Glucose tolerance test (GTT)
160 mg/dl bet 15- 30 min

Rate of glucose during the five phases of glucose homeostasis .
I
II
III
IV
V
Origin of
blood
glucose
Exogenou
s
Glycogen
Hepatic
Gluconeogen
sis
Hepatic
Gluconeoge
nsis
Glycogen
Both
Hepatic and
renal
Gluconeoge
nsis
Both
Hepatic and
renal
Gluconeoge
nsis
Tissue
ussing
glucose
All
All except
liver
Muscle and
adipose tissue
at diminished
rate
All except
liver
Muscle and
adipose
tissue at
diminished
rate
Brain, RBC,
renal
meulla.
Small
amount by
muscle
Brain at
diminished
rate , RBC,
renal
medulla.
Major fuel
of brain
Glucose
Glucose
Glucose
Glucose,
ketone
bodies
Glucose,
ketone
bodies
Enzymatic – chemical method

Glucose oxidase method:
Oxidation-reduction reaction (alkaline
copper reduction method):


This method depends on the reducing properties of glucose which reacts
with cupric ions in alkaline medium producing the red colored cuprous
oxide that can be measured colorimetrically
When heated with o-toluidine and glacial acetic acid, glucose reacts with o-toluidine
to form N-glycosylamine. This compound has a blue-green colour and its
absorbance can be measured at 625 nm.


Take all absorbencies at 630nm against blank
630nm is the wavelength of red light, the
complimentary color of green, which is the
color of the imine complex product
1.
2.
3.
Half fill 500 ml beaker with water and put it
on the hot plate to boil.
Take three clean test tubes and label them:
TEST, STANDARD and BLANK.
Add in each tube 5 ml o-toluidine (from a
burette).
4.
Then, very accurately, pipette:
– 0.1 ml blood into the tube labeled TEST.
– 0.1 ml standard glucose solution into the tube
labeled STANDARD.
– 0.1 ml distilled water into the tube labeled
BLANK.
5.
6.
Shake the tubes and put them in the boiling
water for 10 minutes. Remove the tubes,
cool them
Read the optical densities of the TEST and
STANDARD against the BLANK.
 Calculations
The concentration of glucose in the
standard solution is 100mg/100ml.
 The concentration of glucose in urine is given
by:
O.D. TEST
––––––––––––––  100 =
O.D. STANDARD

mg Glucose 100/ml blood