Measuring 2 hours after a meal... how would you make that more clear?

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thezak posted on Wed, Jun 15 2011 7:12 AM

a) What is the range of time for an accurate reading when you're told to measure blood glucose 2 hours, 120 minutes after a meal?... would 2 hours 10 minutes, 130 minutes after a meal give an accurate reading too?... 2 hours 20 minutes, 140 minutes after a meal?... what about 1 hour 50 minutes, 110 minutes after a meal?... within 20 minutes before or after the 2 hour mark?... within 10 minutes before or after the 2 hour mark?... or even narrower a range of the 2 hour mark?... or at least 2 hours after not before the 2 hour mark?

b) What is the reason for doing it 2 hours after a meal?...

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Answered (Not Verified) nance replied on Wed, Jun 15 2011 8:32 PM
Suggested by psb

Doctor should have some answers for you, but, I would think that the answer to question a) would vary slightly from time to time and day to day due to various individual and circumstantial factors.  That is the reason why I consider the 2 hour postmeal test time to be an "approximately" good time for me to test.  As for question b) the reason for doing it 2 hours after a meal: that's the time when blood sugar is back to normal in people who don't have diabetes, and what I like to aim for after my postmeal exercise around the 1 hour postmeal point.  We and our doctors can use that number to determine how well our management control methods of diet, exercise, and/or meds are working, and make adjustments accordingly as we go along meal to meal, day to day, etc.  How are you doing so far, Thezak?

Nance, T2 dx 7/98; diet and exercise/no meds 11 yrs; 500mg Glucophage XR 4/day, 5mg Glucotrol XL 3/day; A1c av. in 6s.  Treadmill, elliptical, biking, Arc trainer, dumbbells, other resistance moves -- 30-60 minutes a day.

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zrebiec replied on Fri, Jun 17 2011 4:34 PM


If only diabetes treatment was so precise! Not only do blood glucose levels continually fluctuate, but blood glucose meters have a range of inaccuracy, and many factors in addition to food may effect the result. So exact minutes and numbers matter little. Take for example, continuous glucose monitors that provide a constant stream of data - the numbers in themselves are less important than the trends. So blood glucose checking is more like a compass that gives you information to help decide on which direction to go. I often suggest that people think of blood glucose checking as a personal scientific experiment that helps you to understand how your body reacts to various foods and activities.

John Zrebiec, MSW, CDE

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RobertIA replied on Fri, Jun 17 2011 5:00 PM

John Zrebiec gave you an excellent answer; however, there is more.  Postprandial reading are important also for determining how different foods affect your body and whether to delete a food from your menu or try reducing the serving size.  Another key is the amount of fat contained in the food.  The pizza effect is an example.  Normally at the 2-hour mark you will think, good - that did not affect me.  Wrong, if there is a lot of fat, the spike can be anywhere from 3.5 to 5 hours after first bite.  This again will vary from person to person and that is the reason for the variance of time. 

This is why, if you can afford the test strips for a period, test at half hour intervals starting at one hour through three hours for normal foods.  (Some recommend every 15 minutes, but that should not be necessary).  You don't need to do this after every meal, just when the carb count is higher than maybe it should have been or you are suspicious of the food and want to know how it affects you.

Once you see how your own body reacts to the different foods, then you can go back to testing at the times when you saw the blood glucose readings at or near the peak.  Generally, I suggest that the increase from premeal (or fasting) to after meal readings not be an increase of more that 40 points.  Example:  fasting (or pre meal) of 106, 2 hour post meal 146 is the maximum you are wanting.  Others will allow more, but for excellent blood glucose management I follow the 40 point increase rule.  No, this is not what ADA recommends.  They recommend a reading of no more than 180 as the upper limit.  I personally reject this because with the meter variances you could actually be more that 180 by up to 20 percent.

John used the word activities, but I prefer the word exercise.  This always if good if you are medically capable of exercise.  I am not saying it has to be running, as walking, swimming and even dancing can be helpful.  Find something that you enjoy doing and just do it.

Type 2 (10/2003)   Lantus and Novalog   Now added Metformin      Retired


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Biomass Pellet Mills

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shortie replied on Thu, Jan 5 2012 5:54 AM

"So blood glucose checking is more like a compass that gives you information to help decide on which direction to go. I often suggest that people think of blood glucose checking as a personal scientific experiment that helps you to understand how your body reacts to various foods and activities."  John Zrebiec


I like that answer John....very helpful.  Thanks.  I copied and pasted it here in quotes in case someone else missed it back in June.  I still do not like the format of this blog cause I miss great posts---like this one of yours.Yes



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Camilla replied on Sat, Feb 18 2012 10:02 AM

I would keep it simple. If you eat at 7pm make sure to check at 9pm. A few minutes makes no real difference. By checking this post prandial level you are seeing how your body dealt with that meal. The level should be 6.7mm maximum (that is my rule). If it is higher than that it indicates you need to eat less carbs in your meals. Best not to let it ever be above 7.8mm as that is the level that damage to the body is known to begin.

The ideal would be to stay around 5mm all the time with just small spikes up to about 6mm after meals. Completely normal people stay like that and always get back to below 5mm within 2 hours of eating. So if we can keep our bg at normal levels we can usually stop worrying about complications and enjoy good health.

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amrad replied on Sat, Feb 18 2012 4:58 PM

I usually check about 3hrs after a meal (unless I feel funny). For me that is when the blood glucose seems more accurate, and after the humalog has done it's job.

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