March 11, 2010

One Hour Blood Sugar Test is Best Predictor of Future Diabetes Risk

A study just published in the journal Diabetes Care confirms what I have suspected for a long time. The one test that gives the best indication of whether a person is in the process of developing diabetes is not the fasting glucose test used by 99% of family doctors. Nor is it the two hour value found on an oral glucose tolerance test--which has long been the gold standard endorsed by the American Diabetes Association.

What best predicts diabetes in people who are in that middle ground of not normal but not frankly diabetic is the result seen on a blood sugar test taken one hour after a glucose challenge--i.e. after eating a significant amount of carbohydrate.

You can read this study here:

Minimal Contribution of Fasting Hyperglycemia to the Incidence of Type 2 Diabetes in Subjects With Normal 2-h Plasma Glucose. Muhammad A. Abdul-Ghani. Diabetes Care March 2010 vol. 33 no. 3 557-561. doi: 10.2337/dc09-1145

In this study the researchers looked at the records of 3,450 subjects who started out with 2-hour plasma glucose concentration <140 mg/dl.[7.7 mmol/L] These subjects were participants in the San Antonio Heart Study (SAHS) and the Botnia Study for 7–8 years.

The researchers found that while incidence of type 2 diabetes at follow-up was related to the fasting, 1-h, and 2-h plasma glucose concentrations,
... when the 1-h plasma glucose, but not 2-h plasma glucose, concentration was added to the model, FPG [fasting plasma glucose] concentration was no longer a significant predictor of type 2 diabetes in both studies (NS).

When subjects were matched for the level of 1-h plasma glucose concentration, the incidence of type 2 diabetes markedly increased with the increase in 1-h plasma glucose, but the increase in FPG was not associated with a significant increase in the incidence of type 2 diabetes.
I get a lot of mail from people whose home testing is showing blood sugars well over 140 mg/dl (7.7 mmol/L) but whose doctors insist they are "fine" based on their fasting glucose readings.

If you fall into that category, and are having trouble getting your doctor to take your concerns about your blood sugar seriously, track your one hour blood sugar test results and if they are routinely over 140 mg/dl, print out this abstract and take it with you to your appointment.

You can learn how to use a blood sugar meter to test your blood here:

Am I diabetic? How to test your blood sugar to find out.

There is a less common variant of diabetes usually seen in males where the fasting blood sugar is very high but post meal blood sugar is not. If you have normal post-meal blood sugar, but see fasting blood sugars heading towards 120 mg/dl (6.7 mmol/L) you might be developing diabetes in this manner. Over time it may proceed to full fledged diabetes. Because most family doctors diagnose diabetes based on fasting tests people who develop diabetes in this pattern are more likely to have their diabetes diagnosed early.

You can read about what research has revealed about the different patterns in which diabetes develops and the likelihood of having your blood sugar dysfunction progress to diabetes HERE .

But what if your blood sugar is not going over 140 mg/dl when you eat carbohydrates? Unless your fasting blood sugar is near 120 mg/dl, you are fine. This sounds obvious, but I get a surprising amount of mail from people who have normal fasting blood sugar and normal one hour readings who are convinced there is something wrong with them. There may be, but it is usually not because they are developing diabetes.

That's because normal people's blood sugar fluctuates and may reach the upper 130s an hour after eating and then drop back to normal. The only time you might have a valid concern if your blood sugar at one hour is spiking into the 130s is if it is still in the 130s two hours after eating and even three hours after eating.

This would suggest that your body is having trouble with its second phase insulin response, which you can read about HERE. But this is rare. The most common progression to diabetes begins with one hour readings over 140 mg/dl that resolve or even produce reactive hypoglycemia. This then proceeds to readings over 140 mg/dl that stay over 140 mg/dl for another hour or two.

Though this is technically the "prediabetic range" researchers now know that the incidence of neuropathy, heart attack, and diabetic retinopathy all start to rise as one hour blood sugar goes into the range over 140 mg/dl. (More about that HERE and HERE)

If steps aren't taken to lower blood sugar when it is in the prediabetic range it may rise eventually into the official diabetic range--over 200 mg/dl. But it is very foolish to do what too many family doctors do--ignore oncoming diabetes until a person has an official diagnosis.

That's because the interventions that lower blood sugar are so much easier and more effective when you begin them when blood sugar is only modestly abnormal. When you are only seeing spikes slightly above 140 mg/dl at one hour, usually all it takes to lower blood sugar is to cut down on the amount of carbohydrate you eat at each meal.

Because blood sugars over 140 mg/dl are toxic to the beta cells that produce insulin and can, over time, kill enough of them to make you permanently diabetic, taking steps early can keep your diabetes from progressing, whatever your family history might be.

And because the most effective intervention is one that requires no prescription or help from a doctor, there is nothing to keep you from embarking on a program of healing whether or not your doctor takes your mildly abnormal blood sugars seriously.

You'll find detailed instructions for how to lower your blood sugar safely on your own here:

How to Get Your Blood Sugar Under Control

39 comments:

RLL said...

Doctors could apply this so cheaply and effectively. Home style meters would be entirely accurate enough, and people could eat a MacDonald's pancake breakfast an hour before they got to the office, at the end of the appointment they could even do a two hour reading. If they needed to do some fasting tests they could be alternated from year to year.

Jenny said...

It should be easy. But when I have run into doctors or nurses with meters--which hasn't happened much, they have sometimes been years out of date. Just two years ago I went to the town nurse who was running a diabetes screening, thinking I could double check my meter. She had what had to be a 10 year old meter--the old kind that uses tons of blood, old strips, and her meter read about 40 mg/dl lower than mine.

That meant of course, she was missing diagnoses left and right.

sonny said...

I get spikes of near 180 after I eat oatmeal and most cereals, but no significant spikes (maybe 120)with other foods.
Fortunately after reading your blog and the heartscan blog I am in more control of my diet, probably just in time.
Thanks!

Liz H. said...

I'm a LADA, and if I didn't shoot insulin, my blood sugar would be way over 600 mg/dl(That's as high as the one touch ultra meter goes!) But, years ago, my one hour blood sugar was way over 200 at the frist hour on a glucose tolerance test, and the doctor said "That doesn't mean anything. You are not diabetic." I figure my beta cell were beginning to die from autoimmune attack then, but it was ignored.

Athena M said...

I routinely test my blood sugar now that I am "pre" diabetic and it always spikes very early, sometimes 30 minutes after my first bite (or 20 after my last bite). In one hour it's on the way down, and at two hours it's gone back down to a low range. I've read your book and I'm trying to figure out what it means about my physiology. Do those 30 minute spikes count?

Jenny said...

Liz H. I had a similar experience--my blood sugar tested at 240 mg/dl on the doctor's blood calibrated meter in the office, but she told me it was "nothing," because my fasting blood sugar was around 100.

Athena. Years ago I read a study that said that the 1/2 hour spike was the only one that did NOT correlate with complications if it resolves. That seems to be what these more recent other studies suggest too.

Betty said...

So what are the implications of this finding in terms of testing? Should one test at 1 hr or 2 hr? If I test at 2 hr I may miss the spike. Would splitting the difference to 1 1/2 hour be better and what would be the target then--130?

Jenny said...

The implications for those of us who already test aren't big--mostly that 1 hour readings will generally be higher than 2 hour readings, which we all know.

The significance is for diagnosis. Because so many people with serious pre-diabetes end up with reactive hypos 2 hours after a very high spike--they may be told they are normal based on that two hour low--or that low might be 139 after a spike to 250--and they'll be told they're normal again, which they aren't. Any repeated blood sugar reading over 200 is diagnostic of diabetes even according to the ultr-conservative
ADA.

There are several very good reasons for testing at 2 hours, but if you aren't using insulin and have limited strips, the 1 hour reading probably is more informative unless you are eating pasta or pizza which are notorious for producing later spikes.

Stefan Sjodin said...

I notice that coffee rais my bloodsugar levels. If I dont eat anything except coffe in the morning my bloodsuger goes up.

Im trying to lose weight by burn fat, so glucagon is my friend. Is there anyone knowing if coffein rais bloodglucos via adrenaline/cortisol or by blocking insulin?

Jenny said...

Stefan,

I notice the same thing. If you aren't putting sugar in your coffee, it may well be adreniline. There is only about 1 gram of carb in a cup of black coffee and 1 more in cream or half and half. If you had no insulin production at all that could raise your blood sugar 5-10 mg/dl depending on your weight. But most Type 2s can handle 2 grams without a spike.

nonegiven said...

I just assumed the spike from coffee first thing in the morning was from a liver dump. You're taking in a little something but not very much so you aren't getting your insulin going so you get the glucose spike because your body thinks it's starving.

Rachael said...

I have been having morning readings of 115-120 most days, though my pp readings are 95-120 if I eat low carb. I was wondering if it's because of my mild sleep disorder raising my stress hormones in the night. Like the coffee? I have tried a protein snack at bed time, but it makes no difference.

Rachael said...

Well, I did the home oral glucose tolerance test with a cup of rice today and was over 200 at an hour. So I guess my high fasting levels are because I am diabetic, not because of stress hormones. I ate 150 grms of carb a day for three days first and got 175s after meals. So that's that.

Anna said...

For folks who are self-testing, it helps a lot to do a few "test" meals with very frequent tests (every 15-20-30 minutes?) for several hours and graph them out. I know that's a lot of test strips, but the data they can yield is probably well worth it. And it's "real world" testing that represents daily life instead of the artificial factors of a GTT in the lab.

PRIVATE said...

Hi, your blog is very informative, glad I found it ! I have a few questions and I'm hoping someone can help.
I was told that in order for the GTT to be accurate, you have to eat normally 3 days prior, but I wasn't aware of that. I wasn't eating very much and I was eating low carb because I've become so carb intolarant I can't even look at carbs or eat many other foods for that matter !
So anyway, I had the test and the results from my glucose meter were higher then the test results, (which is weird), the results at the one hour mark were 12.2 mmol/L and at the end of the two hour mark it was 8.4 mmol/L. Does this mean I'm already diabetic or about to be ? I have so many symptoms of diabetes but the results are confusing. I also have high insulin, (hyperinsulinemia).

Jenny said...

PRIVATE,

Eating low carb before a glucose tolerance test will push the results up a bit. That said, a normal person would NEVER go over 11 mmol/L no matter what they were eating. I would treat that test result as evidence that your glucose control is damaged. However, if you are controlling well with a low carb diet, keep at it.

It is the daily exposure to high blood sugars, usually after meals, not any underlying condition that causes diabetic complications. Control the blood sugars and your early diabetic symptoms should abate.

PRIVATE said...

Thanks so much for responding !
I thought that with all the symptoms I have that I was already diabetic. Can a person who has severe insulin resistance, (or on the verge of diabetes) have blurry vision, hunger, thirst, and rashes on the skin ?
I also find so much information out there really confusing.
For example, if the 2 hour test goes above 11 mmol/L then you have diabetes, but mine didn't so I'm prediabic.
Then there's other info that says that if your one hour test goes over 10 mmol/L and the two hour goes over 8.3 mmol/L then your diabetic. So that means that I am because the one hour went to 12.2 mmol/L.
Oh man, this is all so CONFUSING !

Jenny said...

PRIVATE,

Ignore the confusion and concentrate on what matters.

What blood sugar levels are associated with the development of heart disease and diabetic complications?

Click HERE to find out.

Blurry vision can be caused by fluctuating blood sugar levels. It is different from the irreversible retinal damage caused by diabetes which has no sypmtoms until you have eye bleeds. Blurry vision resolves when you lower blood sugar.

Rashes often come from yeast which is promoted by high blood sugar.

Weight gain and exhaustion can come from high blood sugars and insulin resistance, but also from Thyroid disease which can also increase insulin resistance.

Find yourself an endocrinologist as they are often more helpful than family doctors for blood sugar and thyroid problems.

PRIVATE said...

You know it's funny that sometimes a complete stranger can be so helpful rather than the people who are in your life or the people who you know very well. I'm so appreciative when I get even a little help from anyone because so many doctors and endocrinologists I've seen have not been helpful at all. Thanks again ! By the way, what does your exercise routine look like ? Are you working out hard every day ?

Jenny said...

PRIVATE,

I have some serious tendon and lumbar disc problems, so I don't work out. I walk when I can and garden. Though it has many benefits, my experience proves exercise is not necessary for either weight loss, weight loss maintenance, or blood sugar control.

Rachael said...

PRIVATE, Jenny is such a wonderful resource, do listen and be reassured by what she says! You sound like me, I am borderline pre/diabetic, high insulin. I have managed to get my blood sugar down to a level where I shouldn't get too many complications and Jenny's recent post about the average and post meal being important make a lot of sense. Good luck.

PRIVATE said...

If I don't exercise my blood sugar is wildly out of control. I think exercise is really important, unless you have info that says otherwise :-)

Jenny said...

PRIVATE,

We all have different things going on.The usefulness of exercise varies greatly. When I have been able to do vigorous exercise it hasn't made any appreciable difference in my blood sugar, but I'm not insulin resistant. For some people exercise will greatly reduce insulin resistance. Others, who have mitochondrial defects won't see much impact, either.

There are some interesting studies that document the impact of the mitochondrial defects on how useful exercise may be to an individual.

PRIVATE said...

I'm still concerned that the OGTT didn't diagnose my diabetes. My blood sugar is much more uncontrollable now than it was a year ago but my results don't reflect that. (only my glucose meter was higher). I'm so carb intolerant it's not even funny, sometimes I barely eat anything all day because food in general bothers me. I'm afraid that my low carb diet and lack of eating normally may have cleaned up my results and made them look as if I don't have diabetes. I'm also frequently hypoglycemic.

PRIVATE said...

Sorry to post again but maybe my posts can help others as well who are going through the same thing I am ;-) Anyway, I'm assuming that the OGTT will diagnose diabetes no matter what you've been eating (or not eating)....isn't that what the test is for ? To challenge your body and see how it handles sugars ? I'm clearly pre-diabetic with very high insulin, but still not convinced that the blurry vision, rashes, etc. are pre-diabetes related.

Jhakaas said...

This is one of the most informative blog I found yet……….
I am highly confused…..Pleaseee… help……
On 30th march one of the doctor by chance checked my blood levels a1c was 8.6, random 3 hours after meal was 124 & urine was 4….. doctor shockingly adviced me that I am diabetic…….
I am 34 yrs male & was having very bad food & sleep for last one year till that day. Over eating with junk food & working day/night……..
Next day I came to normal healthy food & yoga, 3 weeks later from 21st april, I started home testing everyday, My fasting is mostly between 90-102, did GTT at home 1 hour 180 & 2 hour 129,
After good meal (70-100 grams of carb) 1 hour 130-160, 2hours 115-140
A1c on 28th may was 5.9 (2 month from 1st test)
I am confused , am I diabetic & already crossed the point of no return ? or still on borderline & it can be cured permanently at this times ?
I hope you will help……….

Jhakaas said...

This is one of the most informative blog I found yet……….
I am highly confused…..Pleaseee… help……
On 30th march one of the doctor by chance checked my blood levels a1c was 8.6, random 3 hours after meal was 124 & urine was 4….. doctor shockingly adviced me that I am diabetic…….
I am 34 yrs male & was having very bad food & sleep for last one year till that day. Over eating with junk food & working day/night……..
Next day I came to normal healthy food & yoga, 3 weeks later from 21st april, I started home testing everyday, My fasting is mostly between 90-102, did GTT at home 1 hour 180 & 2 hour 129,
After good meal (70-100 grams of carb) 1 hour 130-160, 2hours 115-140
A1c on 28th may was 5.9 (2 month from 1st test)
I am confused , am I diabetic & already crossed the point of no return ? or still on borderline & it can be cured permanently at this times ?
I hope you will help……….

Jenny said...

Jhakaas,
With blood sugar there is no "cure" only control. You can keep your blood sugar in the normal range and avoid all diabetic complications, but if you eat a lot of carbohydrates your blood sugar most likely will go back up and over a period of years cause many problems.

So focus on keeping blood sugar normal, and you are doing all you have to do no matter what the underlying condition.

Jhakaas said...

Thanks for your reply........

With the healthily normal food i was normal stright on...In my case what do think how many beta cells already died ? i am overwheight & no family history of DM.......
pl advice.......

Jhakaas said...

Thanks for your reply......

I have adoubt....as with healthily normal food i was normal stright on.... what do you think that how many beta cells already dead as i dont have family history of DM & i am overweight....main reason seems to be overeating and inactivity....
thanks
Jhakaas

PRIVATE said...

I just read in a book about diabetes (not sure if you want the name of the book posted), but it states that when doing the GTT, if during the first hour it's over 10 mmol/L, and at the end of the first hour it's over 11.1 mmol/L, and at the end of the second hour it's 8.3 mmol/L then you are diabetic.
Also, do you know why the meter I tested with had higher readings then the blood tests I took ? According to the above criteria, if I go by what my meter results were then I am diabetic.
Then it goes on to say that if you have high fasting insulin during the Glucose insulin tolerance test then again you are diabetic. Does this make any sense to you ?

Susie Lockhart said...

I just had an oggt. Blood was drawn at o 60 120 and 180 minutes. I used my meter to test also. 0 minutes - 91, 45 minutes 339, 60 minutes 179, 120 minutes 69, 180 minutes ? (I ran out of strips). Because my blood was not drawn at my peak how to I get the doctor to understand that there is a problem. My vision has dramatically decreased in the last 6 months and I continue to suffer from bad headaches. My memory has been horrible. Any thoughts, Susie

Susie Lockhart said...

I just had an oggt. Blood was drawn at o 60 120 and 180 minutes. I used my meter to test also. 0 minutes - 91, 45 minutes 339, 60 minutes 179, 120 minutes 69, 180 minutes ? (I ran out of strips). Because my blood was not drawn at my peak how to I get the doctor to understand that there is a problem. My vision has dramatically decreased in the last 6 months and I continue to suffer from bad headaches. My memory has been horrible. Any thoughts, Susie

Jenny said...

Susie,

The numbers you report would make it clear to your doctor that you have reactive hypoglycemia, which is a very early stage of the process that sometimes leads to diabetes. It is normal to see a very high number early on in a GTT because a huge amount of glucose hits the blood stream so fast, but your body took care of it fairly well.

Your vision problems do not sound like the kind that are associated with diabetes nor does the memory loss. Something else is probably causing them, possibly hormonal changes?

But you are fortunate that your blood sugar is in the range that can be controlled completely just by by cutting down on your carbohydrate intake. I would not stress about it.

Tim said...

Jenny,

I know this post is a little old now, but it's the only thing I've seen that addresses what I've been experiencing and I was wondering if you had any advice or info.

As a result of some family history with diabetes and my own experiences in managing weight, I recently decided to read your book and website and have gained a lot from them. I've begun measuring my levels, and here's what I've noticed:

Fasting blood glucose is fine, always in mid 80s.

After a meal without any carbs, I'm usually in the 90s or barely above FBG at 1 hour, and back to FBG at 2 hour.

After a meal WITH carbs (rice, potato, bread), my 1 hour will usually be somewhere between 100 and 115. But my 2 hour will almost always be HIGHER. Sometimes in the mid to high 130s. Almost never above 140, however. At 3 hours, I will usually be back down to where I was at 1 hour.

So my question is: while my levels never seem to quite hit the danger zone, should I still worry since I show such an irregular pattern, with my 2 hour being higher than 1 hour? Could this mean I have an impaired phase 2 response, as you describe in this post?

Thanks so much for any guidance. Your work is really appreciated.

Jenny said...

Tim, It doesn't sound like you have anything to worry about now. It may be possible that you have delayed digestion. That can happen due to some conditions that affect the valve at the bottom of your stomach.

Check your blood sugar every six months or so, because of the family history, eat sensibly, avoid sodas and other sources of the fructose we know damages the liver and causes insulin resistance, and exercise and you should do fine.

Tim said...

Jenny,

Thanks so much for this. I will continue to keep an eye on things and will of course take all the preventative measures. Thanks again for your great work!

Me said...

Hi all,

I know that this is a rather old thread, but it hits on some questions that I've been searching for answers for.

I am a 36 year old male with a history of great health. In July of 2013, I went to my doctor for a routine checkup (after not going for nearly 5 years which was rather boneheaded on my part). During a blood screen, he noticed that my A1c was at a 5.7, and I had tryglycerides in the 220's. Not good at all. He asked that I take an OGTT. I was unable to take the OGTT for around one month. In that time, I was terribly frightened and began low carb dieting and exercising rigorously.

When I went in for my OGTT, my doc said nothing to me about preparing for the test apart from fasting for at least 8 hours prior. I have read numerous accounts that eating a low carb diet can sway OGTT results. I have also read that stress can also play a part in the numbers. In the three months before my A1c was tested, I was incredibly stressed out by a work situation where I ultimately lost my job and, subsequently, my insurance. I was angry and depressed during much of this time and terrified for my family's future (we're all fine now BTW--great new job working from home).

I guess my question regards how much of an influence these factors can really play in my test numbers, particularly one aspect of the test--the one hour reading.

When my test began, my fasting number was 91 (not too bad). My one hour reading had skyrocketed to 240 (which ultimately landed a diagnosis of Type 2), and my 2 hour reading was 142 (not great, I know).

My doctor immediately made a diagnosis and prescribed meds. I have read elsewhere that a second test is typically required to make a formal diagnosis, but he has not done that.

My fear is that I already know the answer to my question, but I'm just curious if it's worth my time to be retested. I have been checking my numbers for a while now and have had nothing in the abnormal range. I've never had a one hour over 128 and certainly no two hour close to that. I've also lost over 30 pounds since that time through diet and exercise (I was 175 in July and down to 145 in October)--I am 5'8'. I've tested my meter on others (particularly my "prediabetic" mother-in-law), with control solution, and everything seems to check out.

At this point, if I'm diabetic, then I'm diabetic. I just want to have a diagnosis based on an accurate test. Is this just wishful thinking?

Jenny said...

Eating a low carb diet for a few weeks might raise your blood sugar perhaps 20-30 mg/dl, but that 250 was a very high reading, since anything over 200 mg/dl is considered diagnostic. You can be pretty sure that you have some kind of blood sugar abnormality. The gradations between "pre-diabetic" and "diabetic" are pretty much useless, in terms of health, since diabetic complications start to occur when people have blood sugars in the supposedly "pre-diabetic" range.

But it sounds like you are doing all the right things and have regained control, which is all you have to do. So the most helpful way to deal with this is to think of yourself as someone with diabetes who has regained normal blood sugars through the lifestyle changes you have made. Keep doing them and you should be fine. Stop doing them and you go back to being a person with abnormally high blood sugars as truly normal people even when stressed will not see numbers as high as what you got on that GTT.

The very good news is that since you caught the problem quickly, you can expect to have normal health. I doubt a new GTT would be all that informative. It isn't any more useful than meter testing after meals since it is such an artificial test (unless you routinely suck down 70 g of carbs, for fun.)

Also, if your blood sugar has come down because you are taking meds, you want to be very careful about stopping the meds now that your numbers are good. Some diabetes drugs are not healthy, but if you are taking metformin, it could explain both the weight loss and the improved blood sugars.

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