By Dr Joe

To fully understand what causes high blood sugar levels in non-diabetics, it makes sense to go back to first principles of blood glucose regulation.

You will be glad you did, because by the end of this blog post, you will have the fundamental knowledge to connect all the dots regarding why blood sugar may be high in a non-diabetic.

what causes high blood sugar levels in non-diabetics


So, let’s do that, shall we:

Behind your stomach is an organ called the pancreas. The pancreas has a cluster of cells scattered within it called the beta cells.

The beta cells are very important to us. As little in size as they are, their importance cannot be over-emphasized.

Why is this?

Because Beta cells of the pancreas are responsible for producing, storing and releasing insulin when called upon.

You need insulin to survive. Without insulin your cells cannot access the glucose in the blood circulation. Without insulin energy production will cease. Insulin is the hormone that drives sugar from the blood circulation into the cells.

When glucose gets inside the cells, it can then be used by the mitochondria (the power house of the cell) to produce energy. This is the energy we need to perform both basic and advanced everyday activities.

How does insulin interact with the food we eat?
When you eat, digestion of food begins in the mouth. The glucose in the food you eat gets released by the process of digestion via enzymes in your saliva and stomach.

What this means is within a few minutes of chewing your food, blood sugar begins to rise. Of course, the dynamism of this process of digestion varies from food to food.

High glycemic foods will have their glucose released pretty rapidly. Whereas complex carbs for instance are low glycemic in nature. Low glycemic foods will have their glucose released a lot more slowly.

As soon as glucose gets absorbed, it triggers the release of insulin into the circulation to correct blood glucose levels to normal levels.

The trigger point for insulin release is when the blood glucose level hits 100 mg/dl (5.5mmol/l). This is called the First Phase Insulin Release. It is expected that the first phase insulin release should correct the blood glucose level to normal.

Following the first phase insulin response, the beta cells hold back, pause and wait for about 20 minutes to see if blood sugar levels are back to normal.

If this first phase insulin release does not normalize the blood sugar to 100mg/dl (5.5mmol/l), then a second wave of insulin is released by the beta cells of the pancreas to lower the blood sugar level.

This is called Second Phase Insulin Release.

It is also expected that this second wave of insulin release should fix the blood sugar fluctuation back to normal levels.

Physiologically, the combination of the First and Second Phase Insulin release is what prevents blood glucose fluctuations beyond the 140mg/dl (7.0mmol/l) mark.

So, what causes high blood sugar levels in non-diabetics?

Now that you know the dynamics of food digestion, glucose absorption into blood circulation and the expected insulin response, explaining what causes high blood sugar in non-diabetics becomes logical.

So, here it goes:

If you have a fully functioning beta cells in your pancreas that produce, store, and release insulin in response to blood sugar rises when you eat, then a quick response is expected to regulate blood sugar. This quick response prevents unnecessary blood glucose fluctuations.

And this process of blood sugar correction works so efficiently that within an hour and half of eating, your blood sugar levels should return to the fasting blood sugar levels of below 100mg/dl (5.5mmol/l).

In fact, at 2 hours after-meal, both the first phase and second phase insulin release from the beta cells should have your blood sugar levels down to 80mg/dl (4.5mmol/l).

However, if your First phase insulin response and more importantly, your Second phase insulin release is defective or sluggish for whatever reason, then you will have high blood sugar level even if you are non-diabetic. This is actually referred to as Impaired Glucose Tolerance.

Persistent impaired glucose tolerance is actually pre-diabetes.

Impaired glucose tolerance precedes Type 2 diabetes. If your blood sugar level remains high despite your first and second phase insulin release best efforts, such that it hits 200mg/dl (11mmol/l) 2 hours after eating, then by definition, you are now diabetic.

high blood sugar in non-diabetics

Insulin resistance in the making – How does insulin resistance occur?

Your liver cells and muscle cells take up over three-quarters of the glucose produced by your meal. When your beta cells release insulin, the insulin drives the sugar from the blood circulation into the cells.

It is anticipated that the liver and muscle cells should be very responsive to the prompt by insulin to allow glucose inside those cells under normal circumstances.

The more responsive the cells are the more insulin sensitive you are.

However, there is a situation where even though your beta cells show a good first phase response, the amount of insulin released will not be enough to clear the circulating glucose from the blood.

This is because of what is happening peripherally in the receiving target organs – the liver and muscles.

The cells of the liver and muscles become stubborn. They become unresponsive to the insulin released. The liver and muscle cells are resistant to the signals from the insulin to allow the glucose into them.

What happens next is that the second phase insulin release is prolonged. The second phase response is prolonged because the beta cells have to make and release lots more insulin to force a response by the resistant liver and muscle cells.

This lack of response by the liver and muscle cells to allow glucose inside their cells despite a persistent prompt by insulin is described as insulin resistance and is indeed how insulin resistance occurs.

At this stage of the metabolic disturbance, you end up with high levels of insulin circulating in your blood. This is the result of the pancreas working overtime to drive down the elevated blood glucose by secreting lots more insulin.

This is called hyperinsulinemia.

If you have insulin resistance, you most certainly will have high circulating levels of insulin in your blood (hyperinsulinemia).

Why have the liver and muscle cells become unresponsive to insulin?

It is a tolerance issue. Eating refined carb meals for years leads to heavy demand on the pancreas. The pancreas does its job perfectly in the preceding years.

But refined carb meals always need lots of insulin to restore blood sugar to normal. And in the preceding years, your liver and muscle cells always respond positively by letting sugar into them.

However, as the years roll by and our diet remains unchanged, the liver cells and muscle cells become tolerant to the insulin. They therefore become unresponsive due to the tolerance they have developed.

Meaning they’ve become resistant!

And this insulin resistance is the reason your blood sugar is high as a non-diabetic. Because at this stage, your blood sugar is high but hopefully not high enough for you to be classified as a diabetic.

Insulin resistance may persist undetected for a good number of years. Most times insulin resistance may last up to a decade and even beyond. During all of this time, it will remain undetected and you will to all intents and purposes consider yourself as non-diabetic.

In the end, the beta cells will become exhausted and unable to produce enough insulin to drive down the glucose to normal levels. Blood glucose remains persistently high ultimately leading to Type 2 diabetes.

You may be somewhat “lucky” such that you grow new beta cells that will make and store enough insulin to use in the first and second phase insulin release. But you won’t make enough insulin to lower your blood sugar to normal levels within the usual time frame.

The second phase might take a lot longer.

However, your beta cells will make just enough insulin to stop you drifting into the ‘diabetic zone‘ but not enough to normalize you blood sugar. What that means is; you remain stuck in the ‘impaired glucose tolerance’ stage.

This results in metabolic syndrome. Metabolic syndrome is synonymous with insulin resistance. In fact, metabolic syndrome is also known as insulin resistance syndrome.

In a nutshell, high blood sugar in a non-diabetic can be innocuous when it occurs transiently.

However, frequent and persistent high blood sugar in non-diabetic is not that innocent and can be attributed to:

  • Some failure at the level of the pancreas to efficiently produce and release enough insulin
  • Failure of the liver and muscle cells to respond to insulin signalling.

In essence, high blood sugar in a non-diabetic especially when it occurs frequently is likely due to insulin resistance or metabolic syndrome and later on with the build-up of higher blood sugar Type 2 diabetes becomes inevitable.

what foods cause high blood sugar in non diabetics

What foods can cause high sugar in non-diabetic?

Below is a list of foods that can cause your blood sugar to be high even if you are non-diabetic:

  • Bagels
  • Muffins
  • Sports drinks and energy drinks
  • Black tea
  • Coffee
  • Dried fruits
  • White bread
  • Potato chips and fries
  • Green tea
  • Chinese foods
  • Alcohol
  • Regular pasta
  • Yogurt with added sugar
  • Cakes
  • Pastries
  • White rice
  • Baked potato
  • Waffles
  • White chocolate
  • Soda and other fizzy drinks
  • Fruit juices
  • Certain fruits like pineapple, dates, watermelon
  • Candies

Of course that list is by no means exhaustive.

What causes blood sugar to rise without eating?

For the most part, food as you gathered from above, is the main driver for rises in blood sugar. However, life as you know is never a straight line.

There are other factors that can cause blood sugar to rise without eating. Some of that has to do with inter-play of hormones.

Stress hormones like cortisol, catecholamines (adrenaline and noradrenaline), mobilize glucose from the stored glucose in the liver. Glycogen is the stored form of glucose in the liver.

These hormones cause a rise in blood sugar without eating both in diabetics and non-diabetics. Any thing that causes stress to your body will cause your blood sugar to rise.

Prescription and some over-the-counter medications like nasal decongestants can also cause your blood sugar to rise without eating.

Below are some of the causes of high blood sugar without eating:

  • Steroid medication
  • Stressful job
  • Diuretics – pills that make you pee
  • Nasal decongestants containing phenylephrine or pseoudoephedrine
  • Poor sleep

As you tell from the above list, yes, stress can cause high blood sugar in non-diabetics. Stress from whatever origin has the potential to increase cortisol levels in the blood.

And as I explained earlier anything that causes liver cells to mobilize their glycogen stores unnecessarily will raise your blood sugar. Stress will do just that.

Should non-diabetics check blood sugar?

If you’ve read this far, you will have figured that non-diabetics can have blood sugar spikes without the individual being aware of it. And non-diabetics may have raised blood sugar for years without being diagnosed as having raised blood glucose issues.

Your doctor may not suspect you have blood sugar regulation problems unless you have symptoms. Sadly, lots of people stay in the ‘Impaired Glucose Tolerance’ zone for years without symptoms.

That’s the reason at least a third of the adult population are going about their business without actually realising they have insulin resistance. Only the eagle-eyed amongst us will exclude themselves from this raging scourge.

And Guess what…

The best way to ensure your high blood sugar as a non-diabetic is not a fluke but a much more serious condition like insulin resistance is to test yourself for blood sugar level when you eat.

So, yes, my advice is that non-diabetics can test for blood sugar, if you are looking for some guidance on the matter.

You can just do random blood sugar 1 hour and 2 hours after a meal and see where you stand metabolically speaking.

I have a more detailed technique of doing this. It’s called Eating To Your Meter. Go see it on that link. I have it written there in a step-by-step way for easy digestion (no pun intended).

Yes, test your blood sugar even if you are non-diabetic. Your doctor probably won’t do it as you have no symptoms. Someone’s got to…

Suggested further reading:
3 Unique Veggies That Fight Abdominal Fat?