Keto And Diabetes. Why is my FBS still so high?

I have type 2 diabetes. I’ve cut my carb intake to almost nothing, but my fasting blood sugar is still high. Where is all that sugar coming from?

Good news/Bad news

First the good news. I’ve been on a Ketogenic diet combined with intermittent fasting for nearly 6 months. In that time I have lost 90 lbs. My Ha1c went from 11.1 to 6.4. I’m feeling great and I’m rarely hungry.

Now the bad news, well, not really bad, just less good. When first diagnosed with T2D, my Fasting Blood Sugar was above 300 mg/dl. Even with drugs, Metformin and Glipizide, it was still in the 200s. After only 4 months of keto, it was averaging in the 90s. “That’s great news!” You’d’d say. Yeah, but. I tried cutting back on the Glipizide. FBS elevated a little, averaging around 110. Then I ran out of Glipizide and my blood sugar shot up to 137.

I’m back on my regular dosage and things have normalized. This morning’s reading was 84. But I’d like to get off diabetes drugs eventually. I have heard from many other type 2 diabetics that keto has made that possible. But for now, I need to stick with the medication.

Along the glucose trail.

When you eat carbs, the digestive system extracts the sugar, or glucose from them and sends it to the blood stream. Your blood sugar reading goes up. Beta cells in the pancreas notice this and release a hormone called insulin. Insulin’s job is to carry the glucose to all the other cells in the body and open them up to receive it, where the glucose is used as energy. When insulin has performed this task, your blood sugar goes back down

That’s how it works normally. But if there is too much glucose in your bloodstream, the receptors in your other cells become overwhelmed and accept no more, or so we’re told. So the glucose stays in your blood. This is called insulin resistance.

Who’s on first?

Your body burns dietary glucose first. It’s the most readily available energy source and the one it’s most accustomed to. If there isn’t enough in your diet, it turns to the stored glucose in your liver and muscles. It will also start creating ketones from fat as a supplemental energy source. When the stored glucose is gone your body switches to ketones as it’s primary source. But your body, specifically your brain, needs some glucose. If you’ve run out of dietary glucose and stored glucose, your body can start manufacturing it in a process called gluconeogenisis. Fat is broken down into fatty acids which are converted to the necessary glucose. This process is inefficient. It takes 100g of fat to create 50g of glucose. This really burns fat!

So, if you’re taking in glucose in you diet, you’ll burn less fat. If you have lots of stored glucose, and we all do, you can run on it for a while. This is one reason you can have plateaus and high sugar early in keto even if you’re eating zero carbs. There is a lot of that stuff but it is finite. Hang in there.

Insulin Resistance

The theory is that when you eat too much, especially too much sugar and starch. You’d pancreas respond by creating too much insulin. When the cells in your body get thus overwhelmed with both sugar and insulin the receptors begin to resist, and it takes more insulin to open them. Or they don’t open at all. Sugar enters the blood stream, raising blood sugar, but can’t leave through the cell walls. The glucose backs up and the blood sugar rises even more. Deprived of energy, the cells begin to die, causing all the permanent damage associated with diabetes, from blindness to gangrene.

That’s the theory, but it’s really a educated guess. It is an observation that makes sense but has never really been proven. When one sees the sun going down, one can conclude either that the sun is moving or that the earth is rotating. Both conclusions explain the observation but before Copernicus, the moving sun theory made more sense. If the earth were spinning wouldn’t we feel it? Wouldn’t we be flung off?

I use this analogy, not to belittle Insulin Resistance, it’s the best best theory we have at the moment, but only to point out that is only a working theory, not a fact. If new studies cast doubt on it, we need to be open-minded.

Dr Jason Fung, renowned nephrologist and expert on type 2 diabetes, points out that during so called insulin resistance, insulin is bombarding the liver with glucose which it converts to glycogen, leading to fatty liver disease. This could not be happening, he observes, if the receptors in liver cells were resisting the insulin and staying shut. But the receptors are open and receiving like gangbusters. Where is the insulin resistance? Clearly, there isn’t any.

On the other hand, with type 2 diabetes, some cells, most notably nerve cells begin to die causing permanent damage including damage. These cells seem to be starved for energy despite the overabundance of glucose available in the blood.

Clearly something is blocking the transfer of glucose from the blood to the cells. Since insulin is the mechanism for opening up the cells to receive glucose, we call this condition insulin resistance. The exact nature of this resistance is not entirely understood, but it’s effect is clearly apparent.

Meanwhile, back at the blood sugar.

So, with the insulin resistance model, your taking in carbs but can’t get them into the cells fast enough (or at all) so it stays in the blood stream your FBS goes up and stays there. Even if you stop eating carbs, your body has a lot of glucose stored in the liver and muscles and of course, in fat. These stored carbs are converted back into glucose by a process called glucogenolysis, and that glucose enters the blood.

The opposite of glucogenolysis is glycogenisis. Glycogenisis converts excess glucose to glycogen for storage. glycogenolysis converts the glycogen converts the glycogen back into usable glucose.

When you remove carbs from you diet and you start converting glycogen to glucose, some of that new glucose, if fasting blood sugar is high can get to the liver and get converted back into stored glycogen and also to fat. This creates a feed back loop that can keep your blood sugar higher than it ought to be.

Thankfully, if you eliminate or greatly reduce your dietary intake of glucose (carbohydrates), this becomes a diminishing feedback loop. It may take some time for this diminishing to show up in your FBS, but it will happen.

Another process, gluconeogenisis, converts fat to glucose. This only happens when all other sources of glucose are exhausted, but this, too, shows up in your FBS.

What to do.

So, if the problem is not just too much glucose in my blood, but too much glucose in my whole body. The course of action is clear. 1. Don’t add any more glucose. 2. Use up what you have.

Don’t add any more.

This is step one of the Ketogenic diet, the elimination or severe restriction of carbohydrates in your diet. Your brain needs glucose to function properly, but the liver can create all the glucose the brain needs out of fat through Gluconeogenisis. The truth is, we don’t really need any dietary glucose at all. A diet completely devoid of carbohydrates is completely healthy provided you are getting sufficient nutrients from others sources like meat, eggs and healthy fats. Sufficient nutrients, but not excess. In the broadest sense, calories still matter. Whatever you eat, if you eat too much, your body is going to store it.


Use up what you have.

Just keeping your body at 98.6 burns most of it. You’d can use up the rest faster by increasing your metabolism. Exercise helps. The amount of calories you burn in exercise is surprisingly low, but exercise raises your metabolism, so you burn calories faster for the rest of the day.

Studies have shown that intermittent fasting also raises the metabolism. The traditional low fat low calorie “Biggest Loser” diet, on the other hand, actually lowers the metabolism. You’d body adjusts itself to living off of less. It’s called homeostasis. Since intermittent fasting is just that, intermittent, it doesn’t have this same effect. When you stop eating, your body increases your metabolism to give you the energy to got out and hunt.


I got type 2 diabetes from too much sugar in my system over a long period of time. It’s funny diabetes used to be called “sugar diabetes”. ( I don’t know when we stopped or why, but my conspiracy theories I’ll save for another post.)

But the fact is, my fasting blood sugar numbers don’t just show how many carbs I ate in my last meal, but how much sugar is in my blood from all sources. If I have stored a lot of glucose, in what ever format, it’s going to affect my blood sugar for a while. But not forever.

It’s important, to keep your blood sugar from getting dangerously high and staying there. Cutting carbs and medication in combination may be a good way to do that. But I believe in the long run, my blood sugar will normalize naturally once I’ve rid my body of all that sugar. So I’ll keep calm and Keto on.

Leave a Reply

Your email address will not be published. Required fields are marked *