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Pre and Post meal Blood Glucose Readings

G

Gillianc23

Active Member
Messages
26
Type of diabetes
Don't have diabetes
Hi folks

I’m prediabetic and have got the Freestyle Libre 2 for the 2 week free trial. I’m a bit confused about BG pre and 2 hour post meal readings. I’ve read different things in different places. Which of the following is correct?
a) The reading 2 hours after the meal should ideally be back to your pre meal reading.
b) The reading 2 hours after the meal should ideally be equal to or less than 7.8.
c) some other rule?

Other questions:

1) Does it matter how high the spike in between the two readings goes?
2) What counts as a spike, rather than a general undulation up then down? Are there any figures as a guide for this?
3) If you follow any of the Glucose Goddess hacks to reduce the spike, although the spike isn’t quite so high, it takes longer for the glucose to be absorbed so stays in your blood longer, albeit at a less high level, so this will affect your post meal reading - i.e. it won’t be back to normal in 2 hours - how does this interface with a), b) or c) above?
4) The Libre comes with the range for reports already set to 3.9-10, although this can be changed. Is this the correct setting for someone trying to get out of the pre-diabetic range into the normal range? If so, why not 3.9- 7.8? I did try to ask Abbott this but they just kept saying to ask my GP. (Which I’m not going to do. You have to be dying to see my GP).
5) If your reading isn’t back to where it should be 2 hours after the meal, is it ok to continue eating similar meals provided you exercise after to bring the spike down quicker?
6) I’ve been doing VLCHF (<50g carbs most days) for a couple of weeks but haven’t seen a change in weight. I’ve got about 3 stone to lose. I think it’s because I’m eating too many nuts. Any suggestions on how to kick start the weight-loss? (Apart from stopping the nuts?)!

Thanks

Gillian
 
There’s a lot to unpack in your post. I can’t claim to answer all your questions and my knowledge isn’t gospel.

However, for me, I was advised that foods that are ‘safe’ for me and not ‘spiking’ my glucose is less than a 2mmol rise between pre and 2 hour post.. ie pre reading 5.2, 2 hour post reading 6.2 - this is a 1 mmol rise and a decent low carb enough meal.

In addition, ideally, post meal I was advised to be under 8.5mmol.

Further to this, very low carb for me would be under 20g per day. Before I was on insulin I was diet controlled with carbs and the amount of carbs I could tolerate was between 20-50g.. but I class very low carb under 20g. Under 20g is quite strict and not always needed.

These days I’m around 20-40g. We are all different and what your body can handle will vary to mine and other peoples.

Oh and the last part about weight, being low carb has never magically helped me with weight loss - I also need to be in a calorie deficit. For some just cutting carbs is the key. I don’t eat a lot of high fat because I have enough fat for my body to burn
 
The 2 hour reading, is to assess if the carb content was too high. A non diabetic should be back to about the same as before, at 2 hours.
We aim to be no more than 2 mmol above the pre meal reading, so as to mimic normal sugar control as much as possible, but ideally no higher than 7.8 mmol. Great if you can get to pre meal level, very difficult but not impossible for us diabetics.
If the reading is higher than 2 mmol above the pre, then there were too many carbs in that meal for YOU. The action to take then is identify what caused the raise, then lower the amount in that meal next time, or kick it out altogether. You can continue to eat the same meal if you wish, but it would be better long term to avoid those higher readings.
The Libre range is a default setting that can be altered to suit yourself, but unless you are taking any medication to lower blood sugar, then it is redundant as far as type 2 s are concerned. All you need is to be able to track your readings as a guide to how you are doing.
If less than 50g a day is not working, then like me you will need a lower amount to kick you into Ketosis, i needed to go to 20g a day. Once in Ketosis and fat burning, weight will start to come off, and may be rapid at the start. Once fat burning you can start to find the level at which you can stay in Ketosis. It may be your 50g a day, but you need to kick into Ketosis to start it off.
 
Hi @Gillianc23 and welcome to the forum.
There are a range of opinions ( personal, medical, organisational) on the subjects you ask about. So don't worry about the small details - it's the big picture that matters plus what 'feels right for your body' !
a). Ideally for a non-diabetic (who has never been diabetic) - yes!
b). For a pre-diabetic or a T2 diabetic with very good Blood Glucose control - yes ! Or 8.0 , or for those struggling with a high HbA1C and not wanting to reduce too fast (because of potential temporary vision problems as BG drops) even as high as 8.5 .
c). Yes, the spikes no more than 2.0 mmol rule.

Personally to get my T2D under control I used a combination of less than 2.0 mmol spikes at 2hrs from pre-prandial and max 2hr post prandial spike no higher than 8.0 mmol.

1). Not unless you have reactive hypoglycaemia, which is a rare 'rollercoaster blood glucose' condition.
2). I don't know if there is a fixed rule for this, but to me a spike is something caused by something you eat or a medication like insulin which (can)have a rapid BG lowering effect. So I don't count as spikes the general BG raising effect of : lack of sleep, stress, illness, injury, exercise (ye, it can either rise or lower BG), or medications such as statins, steroids etc.
3). I have no knowledge of 'Glucose Goddess, however if you (for example) take alcohol, it delays the processing of carbs (because the body recognises it as a toxin) and so gives priority to making that safe. However the carbs will still eventually get processed. When this happens and how high a spike you get together with how high your BG stays in the background.
4). Most Type 2's just use finger-prick BG meters, so Libre ranges apply mostly to Type 1 diabetics who need to monitor BG under-shoots (hypos) as well as over-shoots (hypers).
5). I wouldn't advise it, because it's tricky to control BG through exercise, though the more muscle on your body the more glucose it can safely absorb.
6). Not everybody loses weight on Low Carb, particularly if they tend to over-eat nuts and/or cheese. Nobody (medics included) fully understands metabolism and weight loss, many don't accept that it's carbs rather than fat that's the reason for so much modern diabetes and obesity, similarly some believe that hormones play a large part in obesity, but the details are not yet completely clear.
Most obese diabetics do lose weight on Low Carb once they get 'fat adapted' i.e. they get their insulin down long enough that their body fat becomes available as fuel.
 
I was diagnosed with T2 over 9 years ago, and by eating a low carb/ketogenic style diet, I'm able to keep my :glucose at high end normal/low end pre-diabetic levels. I lost a fair amount of weight (20 kilos/about 3 stone) in the first few months because although I've always eaten normal fats, to start with I was also burning body fat having cut right down on carbs as my main fuel without actually upping my fat consumption to compensate.

My pre and post meal targets are more or less identical to @ianf0ster's targets of less than 2.0 mmol spikes at 2hrs from pre-prandial and max 2hr post prandial spike no higher than 8.0 mmol. but I aim for a slightly lower 7.5mmols post meal, which according to these recommendations, is slightly lower than top end of normal/bottom of pre-diabetic range. Under the right circumstances I can sometimes get post meal results virtually identical to my pre meal levels - essentially a nice "bonus" for me. I aim to keep below a maximum of 50g carbs a day, often much lower, or occasionally more if I indulge in a bit of "naughty eating", but generally it's non dietary issues (stress, pain, etc) than will cause spikes or longer high levels (e.g. steroids).

I used one of the original Libre sensors for a while, and for the most part saw lower longish humps rather than short sharp spikes, and this is what I aim for (and expect!) due to my main fuel source being more stable slower acting fats/ketones rather than glucose spikes from quick acting short term carbs. I know nothing about your Glucose Goddess or her hacks, but I keep my glucose levels stable by avoiding higher carbohydrate foods that my body no longer tolerates very well.

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I am newly diagnosed Prediabetic, with a relatively low 43 HbA1c so hoping to get things back on track with diet. At the recommendation of a friend, got hold of a Libre for 2 weeks to find out how my body responds to different carbs. Revelatory and helpful- it has helped me change my diet to get my fasting BG level fairly rapidly back down to 'normal' levels. Alas our family favourite squash and sweet potato soup is going to have to be an occasional treat for me from now on....

I'm trying to understand what to aim for more generally, and this thread has been really helpful - thanks to the OP for the excellent and detailed questions and everyone who replied.

The one thing I still dont quite understand is when you speak about spikes at a given time (For example, from above 'max 2 hours post prandial spike no higher than 8', or on the Diabetes UK link you give 'under 7.8 at least 90 minutes after eating'.) Does this mean the spike should not go higher before that time, or it might go higher but come back down again by that time?

For example, my lunch started at 5.1, fairly quickly rose to 9.2, fell to 7.8 at about the 80 mins mark, and then returned to around 5.2 by the 2 hour mark. That appears to 'break' the maximum spike rules, such as 'spikes no higher than 2', but meet the others. Am I correct or am I misinterpreting?

Thanks if any of you are still monitoring this thread!

Chris
 
Everybody spikes when eating carbs, to a degree how high is irrelevant. The only important thing is how quickly your system got the level back down. This is why we aim for no more than a 2 mmol rise at 2 hours post first mouthful, and a maximum of 7.8 mmol. this is an attempt to mimic non diabetic behavior. if you don't drop quickly enough, then the initial spike was too high for your metabolism, because of too many carbs.
 
Thanks, that is really helpful! Squash soup still out, though
 

Sounds like your numbers are getting stable already, 5.1 prior to lunch isnt to shabby


I’m also pre diabetic, I found out in July 23 and I also used the Libre2 sensor. What a great tool.

For what it’s worth I basically looked at around 8 on the graphs as a maximum 2 hours after eating. I soon found this was easy as I cut everything out of my diet that caused a spike. I might have gone a little OTT but that’s me.

I only use a CGM on occasions now, there isn’t any point as my graphs are flat ( yippeee
) but I still have one put away, I’ll use it as and when .

Anyway you sound like you have it sorted , well done and good luck
 
I find the use of the word "spike" often to be unhelpful. Eat carbs and your blood glucose will rise - a rise by itself is not a spike, it's what happens to everyone. The peak will almost certainly be somewhere in the first hour. The issue for us as T2 is how well our systems deal with the added glucose - how long the levels stay elevated. So the test is not to see "how high you go" it's to see whether (given the amount and type of carb in what you ate) your system is capable of dealing with the glucose so that by two hours you are somewhere close to where you started (within 2mmol/l) and not over 7.8 (or 8.5, if that's you preference).

I have this example that I quote far too often, data from CGM - one small latte, starting point 5.3. After 30 mins, 9.5. After one hour, 5.4. After 2 hours, 5.1.

I can cope with that latte. Although between 20 and 30 mins I'm over 9, my insulin system hasn't really got going. It deals with the latte (on its own) and by two hours it's as if I'd never had it. You'll see similar things if you look at CGM graphs produced by people who are non-diabetic.

I would be concerned if instead of 9, I was hitting 19 (which I would consider a spike) and I'd really want to find out why. You might find this an interesting read as well - basically an analysis of CGM profiles for non-diabetic people.

Continuous Glucose Profiles in Healthy Subjects under Everyday Life Conditions and after Different Meals - PMC

This study investigated continuous glucose profiles in nondiabetic subjects. Continuous interstitial glucose measurement was performed under everyday life conditions (2 days) and after ingestion of four meals with standardized carbohydrate content ...
www.ncbi.nlm.nih.gov
 
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