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DIY OGTT

NHS Grampian output the following:
75g Oral Glucose Tolerance Test


It can easily be performed in primary care but a standardised protocol must be followed and laboratory glucose analysis must be used. This test should not be performed during intercurrent illness. On rare occasions two oral glucose tolerance tests may need to be performed before a diagnosis of diabetes can be confirmed.


The patient should maintain an adequate carbohydrate intake (> 150g) for at least three days prior to the test.
Fast overnight for a minimum of 10 hours (water only permitted).

75 g oral glucose dissolved in 250 to 300ml water to be consumed in no more than 5 minutes followed by a further 100mls water.

Acceptable alternatives are;

Lucozade 394ml (73kcal/100ml formulation) or 410 mls (70Kcal/100ml formulation )
Please note that until the end of 2007 there potentially will be two types of lucozade available

Maltodextrins in appropriate volume to provide 75g carbohydrate (e.g. Calsip 150ml)

Blood for glucose estimation to be taken before (zero minutes) and 120 minutes after consumption of the drink.
Urine may also be tested for glucose to estimate the renal threshold, but this does not contribute to the diagnosis of diabetes, which is based on the fasting and two-hour blood glucose results.
The method of blood sampling is important and must be specified: venous or capillary, plasma or whole blood. Venous plasma is most commonly used. (Aberdeen Diabetic Clinic uses capillary glucose).
The patient should remain sedentary and not smoke, eat or drink for the duration of the test.

Interpretation of 75g Oral Glucose Tolerance Test (WHO 2000)


Glucose (mmol/l) Fasting 2 Hour


Diabetes Mellitus
11.1Venous Plasma
12.2Capillary Plasma


Impaired Glucose Tolerance
Venous Plasma < 7.8,7.0 and < 11.1
Capillary Plasma < 8.9,7.0 and < 12.2
 
Bearing in mind your run of HbA1cs, are you doing this to ascertain if the Big D has really gone?
 
By mapping the BG against elapsed time, you can see how high & fast you spike and how fast you recover.
e.g. my last home OGTT, as well as a fasting BG of 5.2 and t+2hr of 5.4, Ifound that I peaked at t= 50min with a BG 0f 10.3 and that it continued to fall to 3.8 before recovering to 4.4.
 
@AndBreathe I'm doing it to confirm that my one and only hba1c that confirmed a diabetes diagnosis is correct. I suspect it was correct but I just need to confirm it and move on.
 
FergusCrawford said:
By mapping the BG against elapsed time, you can see how high & fast you spike and how fast you recover.
e.g. my last home OGTT, as well as a fasting BG of 5.2 and t+2hr of 5.4, Ifound that I peaked at t= 50min with a BG 0f 10.3 and that it continued to fall to 3.8 before recovering to 4.4.
Click to expand...


Does that not confirm you are not diabetic?
 
VinnyJames said:
@AndBreathe I'm doing it to confirm that my one and only hba1c that confirmed a diabetes diagnosis is correct. I suspect it was correct but I just need to confirm it and move on.
Click to expand...

Did you have regular finger prick tests at the outset in the diabetic ranges? If not, what is your personal hypothesis relating to the potentially erroneous initial test?
 
Yes I believe I started finger pricking within 3-4 weeks of diagnosis. I don't have a hypothesis I'm just seeking clarification of what the situation is. At the time of diagnosis I was recently bereaved and my diet and alcohol intake was not very good. I want to know if it was just for 3 months or I do indeed have some insulin resistance. At this stage, I simply do not know.
 
I find it curious that I can be as negative as I wish with NHS treatment of diabetes but it seems that to want a second opinion of my diagnosis elicits a quite different response. It's interesting :)
 
VinnyJames said:
Yes I believe I started finger pricking within 3-4 weeks of diagnosis. I don't have a hypothesis I'm just seeking clarification of what the situation is. At the time of diagnosis I was recently bereaved and my diet and alcohol intake was not very good. I want to know if it was just for 3 months or I do indeed have some insulin resistance. At this stage, I simply do not know.
Click to expand...

Have you dropped any poundage along the way? If so, you have probably improved any insulin resistance present at the time.

I'll be interested to hear how it goes.
 
You also have to bear in mind that fasting readings from capillary blood and venous blood are similar . However, they differ considerably during the post prandial period. Capilliary blood can be 20-25% higher during an OGTT but the difference is apparently very individual. For these reasons, the conversion as in your method above has been not been found to be very reliable.(comes from the WHO and was meant to be used as a guide in countries where lab tests weren't available)
This paper shows how there can be quite a lot of variabilty if OGTTs aren't done to standard procedures (and even when they are)
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3024379/
 
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