Oral glucose tolerance test

lck23 said:

Can someone tell me why you have to fast for 8-12hrs before doing one of the glucose tests that requires you to drink 75g glucose/carbohydrate?

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It is to start us with a "level playing field" wrt carbs before the test. (except the 3 hours awake & multiple bus journeys to attend prompted a massive liver dump )

lck23 said:

Also, what should the different readings be?

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Fasting :
6.1-6.9 mmol/L - IFG
<7 mmol/L - IGT
@2hrs :
> 11.1 -is a diagnosis of diabetes.
> 7.8 and <11.1 - is indicative of glucose intolerance – pre diabetes.
< 7.8 at two hours - is "normal"

Not covered in standard OGTT (but should be IMHO ) is a measurement of when & level of spike of BG to analyse primary/secondary insulin response.

I notice you say you are diet controlled at the moment.
What sort of diet are you on?

lck23 said:

Thank you!!! Would having breakfast and swimming before hand be likely to give you a higher reading?

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It would certainly affect the fasting test they do initially.

lck23 said:

Thank you!!! Would having breakfast and swimming before hand be likely to give you a higher reading?

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Wold certainly foul up the initial fasting reading not necessarily up or down as would depend on carb intake , timing and energy expenditure!

When are you having this test?

lck23 said:

Thank you!!! Would having breakfast and swimming before hand be likely to give you a higher reading?

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you need to eat a minimum 150g of carbs a day for a few days before, no exercise or breakfast, or as you say, a higher reading

lck23 said:

I don't know if you've seen my multiple other threads stressing out as I visited my doctor and he diagnosed me with prediabetes using a glucose monitor not that much different to my Acu Chek Aviva - certainly all it involved was a finger prick and drop of blood on to a test strip...

So I've been annoying everyone in the forum with a million questions :/

So basically all I'm doing is low carb which I was doing regardless in a bid to lose weight!

I thought I'd do a trial oral glucose thing today, but didn't do it currently - I drank 550ml original lucozade (77.4g of glucose) and this was about 3hrs after breakfast (2 petit filou yoghurts and a bowl of apple and blueberry porridge) plus a swimming lesson with my little one... Anyway after I drank the lucozade (which was vile) I pottered around bathing the baby, feeding the boys, going upstairs etc and took readings at 30 mins, 1hr30 and 2hrs15...

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What results did you get?

lck23 said:

So I've been annoying everyone in the forum with a million questions :/ .

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Ick23 Don't stress re questions they help us ALL learn!

lck23 said:

So basically all I'm doing is low carb which I was doing regardless in a bid to lose weight!

I thought I'd do a trial oral glucose thing today, but didn't do it currently - I drank 550ml original lucozade (77.4g of glucose) and this was about 3hrs after breakfast (2 petit filou yoghurts and a bowl of apple and blueberry porridge) plus a swimming lesson with my little one... Anyway after I drank the lucozade (which was vile) I pottered around bathing the baby, feeding the boys, going upstairs etc and took readings at 30 mins, 1hr30 and 2hrs15...

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These notes from another forum: (Have highlighted/underscored errors in your methodology)
A proper clinical test, following NHS procedures, can easily be self-administered at home following the correct procedure, as described below.

You MUST eat at least 150 grams a day of carbs in the 2 to 3 days leading up to the test. See the article below from Dr Eades on why youneed to carb up before an OGTT

• Buy a 500 ml bottle of ORIGINAL flavour lucozade.

• The night before, pour out 394 mls (the amount needed for the test) and leave in a jug to go flat. (makes it easier to drink quickly and put it in the fridge to chill it as this will reduce the sickly sweet taste)

• Fast for 12 hours, starting the night before the test. The test itself should be carried out in the morning.

• Take a BG reading, and note the reading and the time when it was taken. Official advice is to abandon the test if the pre-test reading is 6.1 mmols or higher, but meaningful results can be obtained even if readings are higher.

• Drink the lucozade in 5 minutes, and start testing every 15 minutes if you can afford the strips, or at least every 30 mins if not. Make notes of all your results together with the times when they were taken. Keep testing up to 3 hours after drinking.

• During the period of the test, you must eat and drink nothing, and must just sit down. No exercise. (exercise helps the body to deal with the glucose)

Carbing up for OGTTs
From Dr Michael R Eades
Following a low-carb diet makes one a little glucose intolerant, which is the reason that the instructions for a glucose tolerance test always include the admonition to eat plenty of carbs in the week before the test. Why? Because all the macronutrients–glucose, fat and protein–are broken down by enzymes during the metabolic process. And all the enzymes necessary for the metabolism of the various macronutrients are made on demand but not immediately.

If you are on a high carbohydrate diet, then you will have plenty of enzymes on hand to deal with the carbohydrates you consume. If you switch to a low-carbohydrate diet, it takes a while to manufacture the enzymes in the quantities needed to deal with the extra fat and protein that your metabolic system hadn't been exposed to. This deficiency of protein/fat metabolizing enzymes is the reason people starting a low-carb diet become so easily fatigued–they've got plenty of enzymes on hand to break down carbs, they just don't have the carbs to metabolize. Once they produce the enzymes necessary to deal with the load of protein and fat, which takes a few days, they become low-carb adapted and no longer feel fatigued.


Once people become low-carb adapted then the same thing happens if they go face down in the donuts. They don't have the enzymes on board to deal with the sudden influx of glucose, and, as a consequence, their blood sugar spikes higher than it would on a person eating the same amount of carbohydrate who is already carb adapted.

@lck23 Please stop stressing yourself out, this will do you and your family no favours. You know your daily readings are normal. You are not showing any diabetic levels from what you have shown us on other threads. We can't diagnose you. Please go to the doctors. Only he can give you the proper tests and make a diagnosis.

lck23 said:

30 mins - 8.3

1hr30 - 7.8 & 7.9

2hrs15 - 5.9 & 6.0


I'm having all 3 tests done properly - I just need to book them in :/

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@Ick23
Did you have a starting (time =0) BG?
your classic OGTT would probably score you as normal as you were below 7.8 @ 2 hours but that spike in the first hour would suggest a primary insulin response deficit (as does mine!) so you could be part way to D . A controlled carb/GI diet could prevent further deterioration.
This is not a diagnosis, only a explaination of what I found from my Endo. Go see your Doc, please

settle down you are getting all hypochondriac on us ...you are fine.. you wouldn't get a normal response from the the sugar because you have had had low carb for a while. your first response is pre programmed from recent meals

I think it was @phoenix that put this link up with a test of the same person on LC and HC diet response
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2444943/pdf/brmedj07161-0009.pdf