INTRODUCTION
The glucose tolerance test (GTT) consists of drinking 100 grams
of glucose solution and measuring the blood glucose values every
hour to get a curve. The values obtained tell a lot about the
body's sugar metabolism. The following 10 tables of results are
typical and are interpreted briefly.
A 2 hour GTT is used to diagnose diabetes, but a 6 hour test might also
diagnose diabetes plus hypoglycemia, because symptoms of hypoglycemia occur
after the 5th hour.
Twenty five percent of the normal population will also show a blood glucose
content of less than 50 mg/dl (2.8 mmol/l) but do not show any other
symptoms of hypoglycemia. Therefore, to diagnose a person as hypoglycemic,
not only the blood glucose values are important but also the person must
experience the symptoms of hypoglycemia in the course of the test.
I do not recommend that you should take a glucose tolerance test, unless
you must to diagnose diabetes. You can get a very good idea of your response to glucose by testing yourself with a home glucose meter. Eat
exactly 300 grams of spaghetti, rice, baked potato, or 150 grams of white bread. This is equivalent to ABOUT 75 grams of sugar, which is enough to
give you a graph. Test yourself before eating, then 30 minutes, 60 minutes, 90 minutes, and 120 minutes after eating.
If your glucose is above 130 after 120 minutes (graphs 2, 3, or 4), it would be worth it for you to see a diabetes specialist, because you are probably diabetic or "pre-diabetic" (which is already "diabetic" for me). Repeat the test with exactly 400 grams of spaghetti, baked potato, or rice, or 200 grams of white bread, and take your results to a doctor.
Severe symptoms, including psychotic or neurotic behaviour, might occur during the test. For this reason, a GTT should be carried out in a hospital, or in a doctor's office. Persons who take cortico-steroids, birth control pills, diuretics, salicates (aspirin) or fenytoine (anti-epileptic) are strongly discouraged to try this at home. I feel a hand held glucometer is accurate enough to give a correct diagnosis of diabetes or hypoglycemia, but a hand held glucometer is not considered to be quite as accurate as laboratory tests on whole blood samples.
INSTRUCTIONS
At least three days before the test a high carbohydrate diet has to be
followed (230-300 grams per day). All medication and nutritional supplements
should be suspended a few days before the test, because they might influence
blood glucose metabolism. No meals should be eaten after 8:00 PM on the day
before the test. During the test, no eating or smoking is permitted. The diabetes
test lasts for 3 hours. If diabetes is found, it might be wise to extend the
test to 6 hours to see if hypoglycemia occurs after the 5th hour.
The minimum and maximum range in the curves considered normal (below) are an average. The patient's symptoms are just as important as the actual GTT curve.
TYPICAL GLUCOSE TOLERANCE TEST CURVES
100 grams of glucose dissolved in water is taken at the beginning of the
test. All of the following tests lasted 6 hours, with blood samples being
taken at the beginning, 30 min., 60 min, 120 min, 180, 240, 300, and 360
minutes (0, .5, 1, 2, 3, 4, 5, 6 hrs.)
Glucose in the urine might be an indication of diabetes. The average blood
glucose level at which glucose is found in urine samples is about 170 or 180 mg/dl.
The curves shown below are used to diagnose several blood sugar
metabolism disorders. Actual curves may vary from person to person
and in the same person from month to month. If the measured values lie
within the ranges of the following 'normal curve,' and if no typical
symptoms are present, then it is concluded that the person has "good
enough glucose tolerance".
(Note: To convert the blood glucose level values in mg/dl to mmol/l,
divide by 18.)
For the sake of simplicity, the following graph shows only:
Normal
(Min / Max), Mild Diabetes, Severe Diabetes, and Diabetes with Hypoglycemia. Other typical results are shown only in tables 5 through 10.
INDEX
Note: Tables Commented by Ellis Toussier
1a. Normal Minimum curve according to Seale
Harris
|
Time [hours] |
0 |
0.5 |
1 |
2 |
3 |
4 |
5 |
6 |
|
bGmin [mg/dl] |
80 |
90 |
105 |
90 |
80 |
80 |
80 |
80 |
A "Normal-Min" curve means your pancreas is still in very good shape. Insulin release is strong and sufficient to keep glucose from rising. Keep your pancreas healthy by not stimulating much release of insulin, ie, eat low carbohydrate meals.
Pathologic conditions causing flat or depressed glucose tolerance results:
Rapid uptake of glucose by peripheral tissue results in fasting hypoglycemia. Intestinal malabsorption results in a minimal increase in serum glucose. Hypothyroidism causes a reduced rate of intestinal absorption of glucose. Low renal Tm for glucose reabsorption results in depressed glucose concentrations.
1b. Normal Maximum curve according to Seale
Harris
|
Time [hours] |
0 |
0.5 |
1 |
2 |
3 |
4 |
5 |
6 |
|
bGmax [mg/dl] |
120 |
135 |
160 |
130 |
110 |
100 |
110 |
105 |
The "Normal-Max" response means you are already well started on the road to diabetes. This
is "normal" but it is not good. You are aging faster than the minimum possible. Your
pancreas is still releasing enough insulin, but maybe 10% to 30% of your beta cells are not
functioning. The stream of insulin is not as much as it was before which is the reason why glucose
is rising. You should care for the remaining beta cells by not stimulating release of insulin. To
prevent the advance to diabetes, pretend that you are already a diabetic, and start to take care
of yourself as if you are a diabetic.... Eat like a diabetic... Cut down drastically on carbohydrates.
You might even THINK of injecting insulin to take the burden off of your pancreas.
2. Curve with mild diabetes (Source:
Hypoglycemia, Dr. P. Airola)
|
Time [hours] |
0 |
0.5 |
1 |
2 |
3 |
4 |
5 |
6 |
|
bG [mg/dl] |
115 |
145 |
180 |
160 |
120 |
130 |
130 |
130 |
Your pancreas is already partly shut down... perhaps 40% to 60% of your beta cells are
burned out, and the stream of insulin is not enough to lower glucose quickly. Your pancreas is
working overtime to bring down glucose. For this reason you are burning beta cells at a faster rate
than ever before. The low quality of the insulin is not as good as before, and the long time that
insulin is present to bring down your glucose causes you to become resistant to insulin.
3. Curve with severe diabetes
(Source: Hypoglycemia, Dr. P. Airola)
|
Time [hours] |
0 |
0.5 |
1 |
2 |
3 |
4 |
5 |
6 |
|
bG [mg/dl] |
200 |
235 |
265 |
280 |
300 |
295 |
280 |
270 |
4. Diabetes and hypoglycemia
(Source: Hypoglycemia; P. Airola)
|
Time [hours] |
0 |
0.5 |
1 |
2 |
3 |
4 |
5 |
6 |
|
bG [mg/dl] |
100 |
160 |
220 |
160 |
85 |
60 |
50 |
85 |
This is a curve of a patient that is both diabetic and
hypoglycemic. With such a curve
severe symptoms can be expected.
5. Continuous low values (Source:
Orthomoleculair, 3, 1988, G.E. Schuitemaker)
|
Time [hours] |
0 |
0.5 |
1 |
2 |
3 |
4 |
5 |
6 |
|
bG [mg/dl] |
60 |
80 |
100 |
60 |
60 |
60 |
60 |
55 |
The curve stays under normal levels during the entire
test. A rare tumor, called insulinomia,
may be the cause. In hospitals,
a 3-hour GTT is used in diagnosis.
6. Pre-hypoglycemia (Source:
Hypoglycemia, P. Airola)
|
Time [hours] |
0 |
0.5 |
1 |
2 |
3 |
4 |
5 |
6 |
|
bG [mg/dl] |
90 |
115 |
140 |
100 |
85 |
80 |
70 |
75 |
The curve is typical for a prestage of hypoglycemia. However,
a range of mild symptoms may be
present at this stage. A 3-hour
GTT would not have been long enough to diagnose this type of
hypoglycemia.
7. Mild hypoglycemia (Source:
Hypoglycemia, P. Airola)
|
Time [hours] |
0 |
0.5 |
1 |
2 |
3 |
4 |
5 |
6 |
|
bG [mg/dl] |
80 |
120 |
80 |
60 |
80 |
75 |
80 |
80 |
This curve represents a mild form of hypoglycemia. Within
the hour, the bG level drops to normal
value. During the second
hour, the value is far too low, this is typical in case of reactive
hypoglycemia. Consequently, the curve rises until the normal value
are reached. Because the bG level
drops 40 mg% (mg/dl) within
half an hour, severe symptoms may occur.
8. Severe hypoglycemia
I (Source: Hypoglycemia, P. Airola)
|
Time [hours] |
0 |
0.5 |
1 |
2 |
3 |
4 |
5 |
6 |
|
bG [mg/dl] |
95 |
110 |
120 |
105 |
100 |
60 |
40 |
60 |
During the first 3 hours, the curve is fully normal. However,
this curve depicts a form of hypoglycemia
that often occurs and
causes severe symptoms. The fact that the curve drops more than
20 mg% (mg/dl)
below normal value indicates already that severe
symptoms might well possible be present.
9. Severe hypoglycemia
II (Source: Hypoglycemia, the disease your doctor won't treat;
Saunders, Ross)
|
Time [hours] |
0 |
0.5
1 |
2 |
3 |
4 |
5 |
6 |
|
bG [mg/dl] |
100 |
170 |
110 |
130 |
170 |
125 |
100 |
100 |
This 'sawtooth-curve' indicates a severe form of hypoglycemia,
though values do not actually drop
below normal values. However,
severe symptoms may occur.
10. Flat curve (Source: Hypoglycemia;
P. Airola)
|
Time [hours] |
0 |
0.5 |
1 |
2 |
3 |
4 |
5 |
6 |
|
bG [mg/dl] |
90 |
90 |
90 |
100 |
90 |
100 |
80 |
90 |
This is a flattened glucose tolerance curve. This curve
may be characteric for people who
conduct a dull, monotonous life.
They complain about chronic fatigue, boredom, disinterest and
loss of libido.
