Newly diagnosed pre diabetic, and Freestyle Libra spikes/crashes

robnas said:

Hi all,

I have recently been diagnosed with pre-diabetes, back in January I had a HbA1c reading of 41 which was borderline pre-diabetes. I gave up all sugary foods and eat much better, this continued for around 6 months until the death of my mum and I consequently fell off the wagon a little, no where near as much as what I was already doing through prior to having the result of 41, I had always had a sweet tooth and was a vegetarian for 10 years so eating carbs a lot to help fill me up.

Fast forward to last week when I had bloods done and I’ve moved up to 45 HbA1c so I have pre-diabetes now! Ever since hearing this news I’ve been very confused and feeling down. I have cut out all sugar again and also have cut out simple carbs almost fully along with starting swimming again, I have also got a Freestyle Libre 2 to show me where I’m going wrong, whist this technology is amazing and very useful it’s driving me crazy with worry and obsession with the figures and reports! One thing I wasn’t ready for was the fact I have been eating shredded wheat for 20 years in the belief that it’s the healthiest breakfast you can have but in-fact this spikes me more than a lot of other foods!

I have a few questions if anyone can help me please, it’ll help put my mind at rest!

1. Shredded wheat spikes my blood sugars quickly to around 10.5 mmol/L, this does drop quite fast afterwards and within a couple of hours of eating I’m back down to a normal range (often having a crash), is that ok? Is that what should happen when eating foods? Spike and then drop quickly?

2. I’m not sure what spikes should be when eating certain foods, obviously the challenge is to keep sugar levels down and consistent, but what would be a ’normal’ range, and is this range for pre-diabetics or non-diabetics too?

3. How does spiking work for non-diabetes? Do they have a spike if they eat a cake like us, is it just the time it takes for the spike to go down for us that makes it bad?

Many thanks

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Hi and welcome.

A BG of 41 is normal. Your current BG of 45 is not, and I'd take that as a sign that something's not right. So I'd fully endorse your decision to do something about it.

The issue for many of us with this sort of issue is that we do not process properly the glucose derived from carbohydrates - that's starches and sugars. Typically because we have a problem dealing with glucose entering the body system we wind up with more glucose floating around not just in our blood but in saliva, tears, lymph, etc. High blood glucose can of itself do damage to nerves and capillaries. I had quite severe and painful symptoms with BGs of around 43/44, others can have no symptoms whatsoever with much higher BGs. So it's a bit more complex than just the BG level.

A rise in BG after eating carbohydrate is perfectly normal and to be expected. One small latte will take me to 9.6 after 30 minutes (from the milk lactose), but it's gone by the hour. I don't think it's at all helpful to refer to this sort of thing as a "spike". The attached bit of research shows what happens to the BG of non-diabetics after eating various meals: it goes up, higher usually if it's a higher carb meal. High point reached around 45 minutes after eating, back to baseline afetr 2 hours or so. Normal rise and fall.


As I mentioned above, the issue is how quickly and how well the body's system deals with the extra glucose. Some of it might be used as fuel immediately, but most goes into storage in muscles (mainly) and the liver. If you have insulin resistance, it becomes harder to clear the glucose. The body then produces more insulin which, while it might do the job, also contributes to even greater insulin resistance in future.

So there's nothing about BG being "consistent". It will rise and fall in response to food, but also in response to your liver deciding to add glucose to your system because it thinks you might need it. People report BG going up in the cold, in the heat, in response to stress, in response to illness, all sorts of things not connected with eating.

Personally I don't eat shredded wheat - it is just too carby. That goes also for things like bread, pastry, rice, pasta, most fruit, most root vegetables etc, as well as anything sugary. As you have a CGM, you can gauge what impact different foods have on your BG. You're looking to note the reading before you eat, and then again at the plus two hour mark. This is not about "how high you go". This is about judging how well you can currently handle what you've just eaten. Obviously if your aim is to reduce BG you would tend to reduce the amount of carb eaten, and therefore the amount of glucose produced.

So - if at the +2 hr point you're seeing a figure that is within 2mmol/mol of the baseline figure, and which is not above 8mmol/mol, your system handled the carb in the food. Readings outside this range would indicate that there was too much carb for you to deal with currently. You'll have to learn what works for you, and what foods you can and can't manage. Different things affect people in different ways. I'd recommend keeping a diary and recording food (and any other events, like illness) and also your BGs. That way you can begin to build up a picture.

Best of luck. If this isn't clear, please ask questions - and have a look around the rest of the forum. It's a great source of advice and experience.

robnas said:

Thank you so much for your reply, that really clears up some of my worries/questions!

I have given up all breakfast cereals now as they clearly don't help with my BG levels, the bit that I'm just getting my head around is that some of the foods I saw as healthy in the past aren't good for anyone with pre-diabetes or T2 so our diet has to change, some of the foods I thought were unhealthy and probably still are from a fats point of view don't seem to raise my BG as much as healthier foods. It's a huge learning curve isn't it!

Hopefully I am on the right path though, I've cut back massively on carbs, completely cut out all cakes, sweets, ice creams etc and am also eating foods in certain orders which helps with slowing down the increase. I will get back on the right side of this as I don't want to be in a position where I'm T2.

Many thanks again

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Exactly. I often say that I wish that someone had told me a few years back to forget everything I'd ever been told about "healthy eating". Most of the "healthy eating" advice since around 1980 urges you to eat more carb.


You may well start to find that many carby foods are also highly processed. I eat very little these days that isn't prepared (by me) from fresh ingredients and I batch cook several meals at once to save time. All meals are based around something like meat, fish, cheese or eggs, with green veg alongside. Bear in mind that I'm aiming for a total carb intake of around 20g/day, so you may be able to add in a bit more carb than I do.