Lab 4: Blood Glucose Control
Explain the role of insulin, glucagon and other hormones in BGL control
Explain the negative feedback control of insulin secretion
Explain the mechanism of action of insulin on its target cells
Explain the causes and diagnosis of type I and type II diabetes mellitus (DM)
Explain the use of the GTT in diagnosing DM and interpret GTT results
1) Follow all blood safety precautions (see handout from blood lab).
2) Individual lancets will be disposed of in the sharps container.
3) Don't do this lab if you have pathological hypoglycemia, check with your doctor in
advance if you are diabetic or pregnant.
Fasting BGL should be about 100 mg / dL plasma (range 70-110 mg/dL plasma). After
consuming food, the BGL gradually rises as digestion and absorption proceed in the
gut. As the BGL rises, insulin secretion increases and acts to bring the BGL back
towards the fasting level by increasing transport into target cells.
The glucose tolerance test is used to determine the pattern of insulin secretion. Fasting
glucose levels are determined, and then a known load of glucose is consumed. The
blood glucose level is measured at intervals (15 min to 30 min) for at least 3 but more
accurately for 4 hours. In a normal subject, the BGL should not rise above 160 mg/dL
and should be back to fasting levels within 2 hours. But in anyone with impaired insulin
secretion, fasting levels may be above the normal range, the highest level may be
above 160 mg/dL, the curve peaks later than for a normal individual, and the BGL
returns to the fasting level more slowly (4-6 hours or more).
In a glucose tolerance test, the glucose load is a stimulus for the cells to secrete
insulin, and the drop in BGL over time is an indicator of how much insulin the cells are
releasing. The specific diagnostic parameters are:
fasting plasma plasma glucose 2 hr after
glucose glucose load
normal < 110 mg/dL < 160 mg/dL
impaired glucose 110-140 mg/dL 160-220 mg/dL
diabetes mellitus > 140 mg/dL > 220 mg/dL
Whole blood values are from 20 to 40 mg/dL lower than plasma levels.
Equipment: glucose meter, glucose test strips
Lancets, sharps container
alcohol swabs, Kim wipes, Band Aids
1. Fast for the 5 hours immediately preceding lab (no food after 8:00 am).
You may drink water and diet, non-caffeinated beverages.
2. At the beginning of lab, determine your fasting BGL using the glucose meter
(operation will be demonstrated).
3. Determine your glucose load:
weight in lb divided by 2.2 = weight in kg
load = 1 g glucose / kg body weight
glucose solution = 10 g / oz
weight in kg divided by 10 = number ounces to drink
glucose load consumed = _____________ g glucose at time _____________
4. Use the glucose meter to determine your BGL at 15 min intervals for the first 2hrs
and then at 30 min intervals for another 1 to 2 hours.
1) put all lancets in the sharps containers
2) put all used test strips, alcohol swabs, Kim wipes, etc. in the biohazard bag
DATA CHART: enter BGL in mg/dL for all subjects.
minute actual name name Robert Emma Louise name
0 86 137 68
15 120 154 94
30 131 168 112
45 157 202 101
60 128 244 105
75 125 252 98
90 122 278 97
105 118 255 92
120 91 253 93
150 50 241 99
180 53 204 94
210 63 133 68
GRAPH - Graph BGL in mg/dL vs time for Robert, Emma and Louise. Use a different
color for each person. Pick up graph paper in class.
1. Which of these three is most likely to be diabetic?
2. Which of these three was most likely exercising during the GTT?
3. Which of these three exhibited reactive hypoglycemia?
4. What causes reactive hypoglycemia?
5. See figure 19-15.
a. List the 3 sources of blood glucose
b. List the 3 fates of blood glucose
6. Briefly explain how insulin increases glucose uptake in target cells.
7. This graph shows GTT results for two different people. The lowest curve is a normal
GTT (N) shown for comparison. The top curves (A and B) are from the same person
(Sam) but done under two different conditions.
N B A
0 1 2 3 4
time in hours
a. Is sam diabetic?
b. Which of sam’s gtt (a or b) was done while he was exercising?
c. Explain your answer to b.
d. Where would a gtt curve for a person with insulin hypersecretion fall on this
graph? Circle or underline the correct answer:
1. above curve a
2. between curves a and b
3. between curves b and n
4. below curve n
8. What are the adverse effects of a BGL that is too low?
9. What are the adverse effects of a BGL that is too high? Note that I did not ask you
to explain the problems associated with diabetes mellitus, just the problems
associated with a chronic high BGL, such as might occur in someone with an
10. Name the hormones that are responsible for increasing the BGL.
11. Which tissues are not insulin dependent?
12. Explain how glucagon can cause hyperglycemia.
13. When and where are ketone bodies produced?
What is the effect of ketone bodies on the ECF pH?
What acid/base disorder can ketones cause?
14. This chart compares the effects of insulin and glucagon:
effect on fat (promotes
storage or use?)
secretion in response to a
high CHO meal
15. This chart compares type I and type II diabetes mellitus (DM):
type I type II
insulin levels in blood
defect causing disease