OCTT questions

WilliamEE · Nov 5, 2014

I just have a couple of questions in relation to the Oral Glucose Tolerance Test

1) If someone has been successfully low carbing for quiet some time (i.e. over 6 months and longer) and then has this test, which as I understand it requires a carb intake requirement, over the 3 days prior what sort of affect does this have on the result?

2) Same question, but only low carbing for 2 to 3 weeks rather than a longer period of time?

CollieBoy · Nov 5, 2014

Well, when I was required to have my OGTT , no warning was given by my endo, and the nursing staff who did the test were clueless about the requirement to up carbs to 120g for ~3 days!
I Did the carb upping as i understand that lack of carbs an reduce ability to deal with the carb loading!
BTW my waking fasting was a "normal" 5.4 but the long fasting journey induced a liver dump and I tested @ 6.5 before the OGTT.
my +2hr was 4.9!

Lazybones · Nov 5, 2014

As I understand the OGTT it is conducted on someone who has not changed their life style for a few weeks (possibly 4 weeks) and stuck with what they consider to be their NORMAL diet during that time (it can be LCHF or whatever).
At the test the person will have fasted for the 12 hours or so prior to the test commencing (this is why it's usually conducted in the morning) and firstly a sample of thier blood is taken which forms the initial reference for their fasting blood glucose.
They are then given a specific glucose loading (usually it's 100ml of Lucozade to drink) and periodically at various time intervals a sample of their blood will be taken in order to measure their blood glucose level at that specific time.
Sometimes the samples are taken at 1/2 or hourly intervals for either the next 2 or 3 hours.
From the resultant data of all of these various samples it is them possible to see how well or badly the individual is at absorbing and processing a fixed amount of glucose over a given time period, and from this data it then becomes easier to predict if the individual is a true diabetic, pre-diabetic or non-diabetic from these results.
The individual being tested should as I have stated NOT change their lifestyle or diet in the 4 weeks that preceded the testing and should also be healthy and free of any illness/colds.
I hope this information is of some use and helps clear a few of your concerns.

Enclave · Nov 5, 2014

Lazybones said:
As I understand the OGTT it is conducted on someone who has not changed their life style for a few weeks (possibly 4 weeks) and stuck with what they consider to be their NORMAL diet during that time (it can be LCHF or whatever).
At the test the person will have fasted for the 12 hours or so prior to the test commencing (this is why it's usually conducted in the morning) and firstly a sample of thier blood is taken which forms the initial reference for their fasting blood glucose.
They are then given a specific glucose loading (usually it's 100ml of Lucozade to drink) and periodically at various time intervals a sample of their blood will be taken in order to measure their blood glucose level at that specific time.
Sometimes the samples are taken at 1/2 or hourly intervals for either the next 2 or 3 hours.
From the resultant data of all of these various samples it is them possible to see how well or badly the individual is at absorbing and processing a fixed amount of glucose over a given time period, and from this data it then becomes easier to predict if the individual is a true diabetic, pre-diabetic or non-diabetic from these results.
The individual being tested should as I have stated NOT change their lifestyle or diet in the 4 weeks that preceded the testing and should also be healthy and free of any illness/colds.
I hope this information is of some use and helps clear a few of your concerns.

I had this test yearly .. I was following the nice eating guidelines at that time .. With very little sugar and moderate carbs ... On my 4 th year of being tested this way my Dr almost jumped for joy as it proved I was T2 diabites.. In hind sight I wish I had not had these tests as they did always make me feel very unwell for several days after .. Now LCHF and keeping away from Drs

phoenix · Nov 5, 2014

I don't think it takes even a few weeks for the effect to show . Himsworth showed back in the 1930s that glucose tolerance was altered after just week on a low carb diet ( was the first person to do research on this, with lots of experiment on people and animals, his findings are still quoted in papers ) . Here is the glucose profile showing the results of an OGTT on a 'healthy young male' after a week on a high carb and a week on an high fat diet..
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2444943/pdf/brmedj07161-0009.pdf

Most places say to make sure that you are eating a higher carb amount for 3 days but I have seen a week or longer mentioned.

Lamont D · Nov 5, 2014

I'm on to my fourth in the new year!
I have never been told about what to eat or not what to eat only that I fast, because my fasting is always in the low 4mmols.
I have always had bloods taken before and every half hour for more than 4 hours to see if I hypo after spiking!
Unfortunately, the last test I did go hypo, so my meds were increased!
The reason was because I hadn't had a hyper for so long that my body couldn't cope with such a high glucose level. And I flushed too much insulin into my blood stream to cope with it!
I never had lucozade!!
The first time I had one and I hypoed. They insisted I had a bottle of lucozade to get my BSLs up. However the same thing happened again and I went hyper then hypo again!!
I had to stay an extra couple of hours till I normalised!!!

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