Testing Blood Glucose Levels on a Low Carb Diet – Facts and Myths

Last month Jimmy Moore started testing his blood sugar after eating popular low carb products. Here’s the facts and myths about blood glucose levels when eating low carb.

Do Popular Low-Carb Products Raise Blood Sugar?
Truth About Blood Glucose Tests

Saturday was the first time I heard about Jimmy Moore testing his blood glucose levels after eating some of his favorite low carb foods.

Many low carbers stop by Jimmy's blog every day or two, but I quit stopping by about a year ago when videos became the norm there. At that time, I didn't have a high-speed internet connection, so I wasn't getting anything out of that blog.

Saturday, I just happened to be reading tweets at Twitter and saw that Jimmy had announced that his blood sugar testing results from eating Julian Bakery’s CarbSmart breads was in. Since I now have high-speed access, I clicked on the link he provided, and began to read the post.

It quickly became apparent that in my absence, I’d missed Jimmy’s first test using Dreamsfield Pasta, so I followed the link he provided back to that first experiment. 

When I saw what he actually did – how he compared the coated pasta to regular pasta – I gained a new respect for him. I never thought I’d ever see him confront low-carb products in the way he’s currently doing. 

However, there are a few myths about blood glucose levels and low-carb diets that I need to address here on this blog.

Is Dreamsfield Pasta Low-Carb Pasta?

Many diabetics can tell you from their own experiments that Dreamsfield Pasta digests the same as regular pasta, and that’s what Jimmy’s self test clearly showed as well.

There is no such thing as protected carbs.

However, Jimmy stopped testing his blood sugar after 180 minutes. Pasta takes 5 to 7 hours to digest completely, so most diabetics and pre-diabetics see a sharp rise in glucose somewhere between 5 and 7 hours. 

For those who don’t see that sudden upswing 5 hours later, they generally see much higher fasting glucose levels the following morning.

Both the Dreamsfield pasta and regular pasta curves on Jimmy’s chart are within safe margins for glucose toxicity. You can clearly see that Dreamsfield’s pasta digested slower, but that means potentially higher insulin levels over a much longer time period since his blood sugar level kept bouncing. 

Plus, we don’t know what happened between the significant 5 to 7 hour period.

Are Julian Bakery’s CarbSmart Breads Really Low in Carbs?

When eaten the way Jimmy would normally use bread, Jimmy’s curves fit well within safe margins for glucose toxicity – even when eating regular wheat bread. 

What we learn from his experiment is that his blood glucose levels tend to spike much faster than the average person's glucose would. If you test at 1 and 2 hours, as recommended, you could easily be deceived by the results.

At 1 hour the low-carb breads left Jimmy’s sugar level at just above or just below 100 mg/dl; and at 2 hours, the raisin-free bread allowed his blood glucose level to return to his typical fasting level. The raisin bread stayed about the same as where it was at 1 hour. 

The chart is extremely enlightening, because the 9-grain bread (not low carb) actually gave Jimmy the best blood sugar control.

What's the Real Low-Carb Myth Here?

You might be tempted to interpret these results as Dreamsfield Pasta and Julian Bakery deceiving low carbers. These low-carb breads and pastas must have more carbohydrates than what the label claims. Right?

But that isn’t necessarily true. Blood glucose control doesn’t fall in line with how many carbs you eat. 

That’s the real low-carb myth.

The glycemic index spawned the South Beach Diet and other low glycemic plans, but the folks who participated in the study were healthy non-diabetics. This makes the chart (even the glycemic load chart) useless for those with insulin resistance, pre-diabetes, or diabetes. 

Eating low and lower glycemic foods like berries or even vegetables doesn’t guarantee good blood sugar control.

Problem Testing Blood Glucose When Restricting Carbs

When you eat only low-carb foods, the body down-regulates basal insulin levels, the amount of insulin you store, and the enzymes needed to digest carbohydrate foods. 

If you haven’t been eating carbs and you suddenly eat something like bread or pasta, your blood glucose levels will rise higher than they otherwise would – if you ate that amount of carbohydrates on a daily basis.

Results won’t be accurate – unless (like Jimmy) you just want to test these foods within a low carbohydrate context

If you want to know your true level of glucose control, you must eat carbohydrates for at least 3 or 4 days prior to testing. You can’t just go from 20 or 30 grams per day to 60, 80, or 100 grams without raising your blood sugar levels for a couple of days while your body re-learns how much insulin to store and up-regulates necessary enzymes.

The Role of Food Sensitivities

In my own experience, food sensitivities play a major role in blood glucose control. 

If you have un-diagnosed celiac disease, gluten intolerance, or a wheat allergy or sensitivity, low-carb products can raise your blood sugar higher than is safe, even though it might not raise someone else’s. This is because the inflammation produced by allergies, sensitivities, and autoimmune issues keeps your body in a state of alert.

The body uses extra glucose to heal inflammation and fight off invaders. Higher cortisone levels, triggered by stress, also keep blood sugar and insulin levels elevated, as well. But there is also the strange phenomenon of food individuality.

Since I began testing my glucose levels, I’ve learned that the number of carbohydrates I eat doesn’t accurately predict the amount of glucose produced from food, nor whether or not my body is able to create, store, and secrete enough insulin to handle what I eat. 

It doesn’t predict whether my insulin receptors are working properly. Glucose control depends on what type of defects I have in my metabolic system, and whether or not my immune system is working appropriately.

Thus translates into some pretty freaky results. 

For example:

My daughter-in-law (a diabetic) can eat white rice with her meat and veggies, and her blood sugar stays within acceptable limits. But if she tries to eat the same amount of brown rice, her glucose levels go through the roof. This result is backward to what the glycemic index says should happen.

If I eat 40 carbs of homemade gluten-free oatmeal bread (2 slices like Jimmy ate in his experiment), my blood glucose levels go above 140 mg/dl at 1 hour – putting me in glucose toxicity.

In fact, the homemade gluten-free hamburger bun I tried last week sent my sugar level soaring to 175 mg/dl at 1 hour, and stayed high for 2 hours before dipping back down below 120 mg/dl (the safe zone). 

But –

If I eat a 40-carb baked potato, my blood sugar level only goes up to about 105 and then returns to normal, around 84, by the 2nd hour. This makes white potatoes a perfectly acceptable maintenance food for me.

Everyone is Not Insulin Resistant

The biggest myth floating around low-carb circles today is that if you’re overweight or obese, you’re insulin resistant – period.

Carbohydrates will raise your blood sugar, low-carb diets will automatically correct that, and lowering insulin levels is a good thing. 

However, some of us don’t make enough insulin. 

You might be insulin sensitive – and not insulin resistant. Lowering your current insulin level can result in glucose toxicity if you can't make enough insulin, quick enough, to take care of the elevated glucose. That’s not a good thing.

This is why testing your own blood sugars and finding what foods work for you is essential. You'll never regain your heath if you consistently depend on the results of others to point the way.


  1. Dear Vickie,
    Many thanks for your post.
    But how do I start?
    I've found that eating exactly the same foods on different days produces different results. (maybe stress plays a part?)
    I feel worse after breakfast, but less affects after lunch or dinner?
    Also you imply that previous days eating affects your blood sugar levels?
    I await your response.

  2. Eh-san,
    You said, "But how do I start?" I'm not sure what it is you want to start. Do you want to know how to start a low carb diet?

    Stress plays a very large role in glucose control. Cortisol is a hormone released when we are under stress. Its job is to get fuel as quickly as possible so we have the energy we need to handle the emergency (real or imagined). Its also released about 3 in the morning to start waking us up.

    Depending on our physical condition, cortisol can signal the liver to mobilize stored body fat to fuel glyconeogenesis or it can signal the pancreas to release insulin so the liver will use its glycogen stores.

    Morning is when most people have the least glucose control. Dr. Bernstein recommends eating no more than 6 carbs at breakfast. Mostly, that's due to the cortisol that's released to help us wake up and get moving.

    Feeling worse in the morning could also mean your fasting blood sugar is too high.

  3. I am on the Paleo diet, and to my shock my fasting blood glucose went from 90 before Paleo to 115 after Paleo. That's enough of a warning that something isn't quite as expected that I have a glucometer on order and will start using that. Is there any way to interact with you by email? Do you have a Contact form on some site?

  4. Hi P1,

    Somehow, I accidentally deleted by email from the sidebar. Thanks for asking. I put it back. It's toward the top on the right now.

    Sorry to hear you're having blood glucose issues with Paleo.

  5. There are no “special” foods for diabetes; rather, some food choices are better than others. A healthy diabetes diet is a diet that would benefit anyone, says Alison Massey, RD, LDN, CDE, a registered dietitian and diabetes educator at the Diabetes Center of Mercy Medical in Baltimore. The American Diabetes Association recommends a diet that is low in fat with meals centered around whole-grain foods, vegetables, and fruits.
    Facts And Myths About Diabetes


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