Wednesday, November 08, 2006

When To Test After Meals

When we first received our brand new blood glucose meter the majority of us were told by our doctor or qualified diabetes educators to test twice daily - before breakfast, also known as "fasting" and before the evening meal. Some, not many, of us were also told to test occasionally two hours after meals.

The "us" I speak of are the thousands of newly diagnosed type 2's I've met in cyberspace over the past four years. Over that time, in three diabetes usenet newsgroups, eight Yahoo diabetes newsgroups and a couple of others via the web, I have yet to meet a single newby who was told by their doctor to test one hour after every meal or snack. In fact I've only recently met a few who were advised to test one hour after any meal at all.

So, why do I recommend that we should? Well, I must admit - it wasn't my idea; I learnt it from Jennifer and her Test, Test, Test advice. I also learnt from Derek Paice and his e-book Diabetes and Diet

Any test is wasted if it neither informs nor confirms some information. The tests prescribed by your medics are designed to help them analyse your progress, to assist in their decisions for your treatment - but they do very little to help you personally manage your diabetes. The doctor wants to see your "static" numbers, not the ones that might be very high or low as a result of the carbs you ate, or ignored, at your last meal.

And that's why I add those one-hour post-prandial (after-eating) tests - they help me directly. They are the "dynamic" numbers that showed the direct effect of the food I ate and the exercise I did. I call them one-hour, but the real term should be "peak" or maximum "spike"; mine is one-hour but you'll have to find your own.

I don't think the timing of the spike is as important as it's peak level and duration.

Think about it logically. Why would a spike of 10(180) affect you any differently if it occurred at 30, 60, 90 or 120 minutes? It's duration would be a factor - but post-prandial timing of the actual peak should be irrelevant. It still got to that peak, no matter when it occurred.

So, I learned to find my peak. That is slightly different, but reasonably predictable, with different foods and meal mixtures. Drinks, like OJ, spike me very quickly within 30 minutes and drop just as quickly. Which is why some people use them as hypo treatment. Starchy carbs, without much fat, will spike me in 30-45 minutes. But add fat - and it's about 60 minutes. A normal meal combining moderate fat, protein and low GI carbs leads to a peak at 45-75 minutes for me, and so on. That's why I settled on using the 1hr post-prandial test as my guide, but I occasionally do a 30 minute one if the food was low-fat and high-GI.

As to whether a brief spike causes damage - not enough research has been done. There appears to also be a possibility that spikes have a damaging effect at lower thresholds for type 2 than type 1, partly from anecdotal discussions I've followed over the past four years and partly from the slight differences in results in studies like the DCCT and UKPDS. Let's face it - only type 2 have beta cells to lose anyway. Therefore I am swayed by the reports here, on Jenny's excellent web-page; there is enough evidence to convince me that staying under 8(140) is worth the effort - no matter when it occurs: Research Connecting Organ Damage with Blood Sugar Level

Of course, I tend to always aim a little tighter, so these days I set the level at 7(126) for my one-hour post-prandial maximum. What you do is up to you.

Cheers, Alan

Everything in Moderation - Except Laughter.


Cindy Moore said...

Just found your blog from Regina's blog.

I'm learning new things all the time!! I am a RN, have been for over 30 years, but I'm out of the clinical work now, and have been for about 15 yrs, although I do keep up on research, etc.

What you are being told makes no sense at all!!! The purpose of testing is supposed to be to make sure your treatment is working and the only way to do that is to test AFTER meals!!!

I can understand the fasting reading, but the one before dinner???? Before dinner??? No, it should be after dinner.

I am not diabetic, but have a very strong family history, so I'm following a low carb diet in the hopes of preventing it.

Feeding carbs to diabetics, restricting fat and protein in diabetics, now you're saying that patients are being told to test before meals only??? Insanity!!!

Good luck with your plan...looks like you know what to do!!!

Alan said...

Hi Cindy

I can't disagree with you. To be fair, that's what I was told as a brand-new diabetic. My doc takes a different view these days.

Remember the different reasons for testing. Most medics are looking for the steady-state numbers; but those of us using the meter to fine-tune our menu need the worst-case numbers.

Cheers, Alan

Anonymous said...

Hi Allan, I've read your excellent posts on for years. It's good to see you have a blog now.

The way I think of it is:
1. It's high blood sugar that does the damage. What's high? Pick a number. 140 is the current winner.
2. I test before a meal when I am trying to calculate how many carbs I can eat.
3. I test after a meal because that's when food is digested and sugar is released into my body.
4. What I ideally want is continuous monitoring to determine my BS and when I go over my limit.
5. We don't have continuous monitoring so I have to pick when to test. Realistically I won't test very often after a meal. From experience I notice peaks at different times depending on what I eat. One hour and 2 hours seem to capture the response for most foods. Is the one hour number more important? I don't know, but I do know my 1 hour number and my 2 hour number can be very different. So with an unfamiliar food or meal I do both.

Anonymous said...

My doctors (both my diabetes doc and primary care has me testing as follows, test at all pre meals ant at bedtime (Not Snacks) on any given day test 1 hr and 2 hour after a meal. so I test after breakfest today and tomorrow I would test after lunch. 1 a week take my BG at 2:00 AM My orignal diabetes doctor would only do pre meals. Not very good on the control side.
as well as logging BG the diabetes doctor has me logging carbs, and meals. Went from HgA1C of 11.47 (9/07) to a 6.3 12/07 and 6.4 6/08

Anonymous said...

My doctor did exactly what you said. Test when I first get up in the morning and before dinner in the evening. Therefore, that is what he wrote my prescription for my testing supplies. After reading on ADA and your site here, I am right now in the process of multiple tests throughout the day. I am keeping a log of what I eat, when I eat it, and what my BG levels are various times. It is taking alot of time, but I can see it is definitely worth it. I thought I was doing well for the past year, but now I know better. My A1C was at 6.8 last test but I want it better. I am only on my second day of this and I know I will run out of test strips before I can refill my prescription, but it will be worth it. At least I will know better what to eat and when. I realize there are lots of variables, but it will still be better than what I am doing now.

Thanks for your useful information.


debit202 said...

hi and thanks for your warm welcome to newcomers(me)and your information. I just was checking the forums to see what we are striving for in after meal glucose levels. my fasting glucose is all over the chart-from 76-118 but im trying to grt it more consistent. before dinner testing makes sense to me cuz right now mine is 122because of all the peanutbutter i ate-at least 1/2 lb with 15 carbs of crackers-lol. I am slightly under weightso i dont want to lose weight but dont want to gain weight either. finding meals to fix for 1 person isnt easy and i dont like to cook. any ideas? again thank you for your blog