Blood sugar: More than just a diabetes marker

Most people think of blood sugar as a marker for diabetes risk. As blood sugar goes up, diabetes risk goes up with it.

But blood sugar isn’t just the defining marker for type 2 diabetes. It’s also relevant for heart disease, cancer, dementia, and other diseases of modernity. Your blood sugar is a snapshot of your metabolic health, and your metabolic health is synonymous with your overall health.

Because of this, it pays to keep your blood sugar within healthy ranges. Not only will you feel better (energy levels track with blood sugar levels), but you’ll also set yourself up for a longer, healthier life.

Managing blood sugar is a holistic endeavor. It means doing the things I’m always hammering home: sleeping well, exercising, avoiding refined sugar, and not snacking near bedtime.

For some, this may be more difficult than for others. When you have a bowl of ice cream routinely at 10 PM, it can be hard to cut it out.

I’ll admit that I’m not perfect here, but if you’ve never measured your blood sugar response to different foods, it’s hard to connect with what I’m saying at a visceral level. You generally can’t feel when your blood sugar shoots past 125. It just happens, and your internals pay the price. That said, many do notice vision or even hearing issues as rapid increases in blood sugar can negatively affect our eyes, nerves in our ears, and a host of other tissues.

In this article, I’ll cover why you should care about your blood sugar levels. If you already care, good for you—you’re ahead of the game. But you’ll still probably pick up something useful.

What Is Blood Sugar?

Blood sugar (also called blood glucose) refers to the amount of glucose circulating in your blood. It’s the primary marker doctors use to assess diabetes risk.

Glucose, by the way, is a simple sugar—a type of carbohydrate called a monosaccharide—with the molecular formula C6H12O6. Plants make glucose via photosynthesis, then they store it for energy.

Plants store it, animals eat it. And when animals eat plants, the glucose ends up in the bloodstream as blood glucose.

Glucose is a critical source of energy. Through a process called glycolysis, glucose is converted to pyruvate, which is then converted to ATP and NAD—the two primary energy currencies for the human body.

We need glucose in our blood to live. Dangerously low blood sugar levels (called hypoglycemia) can be fatal. There IS a bit of wiggle room to this story if an individual is fat adapted, but even for the most keto-tastic individual, some glucose is necessary for certain tissues such as red blood cells.

But we don’t have to eat glucose to maintain blood sugar levels. Glucose can also end up in our blood through:

  1. Glycogenolysis: the release of stored glucose (glycogen) from muscle and liver cells.
  2. Gluconeogenesis: the creation of glucose in the liver from materials like lactate and protein.

These are our glucose backup systems. They kick in to help normalize blood sugar lows. But how does the body regulate blood sugar levels? That’s where a critical hormone, insulin, comes in.

Blood Sugar, Insulin, and Insulin Resistance

When blood sugar rises, your pancreas takes notice. And by releasing insulin, blood sugar is decreased to more manageable levels.

Insulin is arguably one of the most important hormones in your body. This hormone helps bring blood sugar out of your blood and into your cells for safe storage. If blood sugar rises unchecked, there are bad consequences.

I’ll talk more about those soon, but insulin helps prevent that. Under ideal circumstances, insulin facilitates the movement of  blood sugar into muscle and liver cells to be stored as glycogen. And if we’ve gotten over our metabolic ski tips, it’s moved into adipose tissue (where excess glucose can increase our fat mass). When your ability to store glycogen maxes out (around 500 grams), insulin starts storing blood sugar as fat.

If blood sugar stays high—say, from eating a high-sugar diet—the pancreas needs to release increasing amounts of insulin to keep up. This is the beginning of a quite complicated condition called insulin resistance.

To worsen the matter, pumping more insulin into the body doesn’t resolve the fact that, on a high-sugar diet, there’s still nowhere for insulin to put the excess blood sugar. Well, nowhere besides fat cells, that is. Muscle and liver glycogen storage is fairly limited. Storing excess glucose and calories in fat is not quite infinite, but close enough for our purposes here.

The result? Blood sugar remains high, insulin levels stay elevated, and the body stays in runaway fat storage mode. This is an operational description of type 2 diabetes.

High Blood Sugar and Chronic Disease Risk

When someone is insulin resistant, their ability to dispose of glucose via insulin is impaired. That means their blood sugar stays high. Fat storage is your body’s last plea to mitigate that. From there, it’s a short hop to the metabolic disease called type 2 diabetes.

The main signs of type 2 diabetes are:

  • Hyperglycemia (high blood sugar levels)
  • Hyperinsulinemia (high insulin levels)
  • Insulin resistance
  • Obesity
  • High triglycerides
  • Low HDL cholesterol
  • Higher risk of death and chronic disease

Let’s zoom in on the last bullet. Type 2 diabetes is bad enough (about 30 million Americans have it), but it can lead to worse situations like:

  • Heart disease. Heart disease is the number one cause of death in type 2 diabetics. High blood sugar drives inflammation that accelerates the formation of arterial plaques.
  • Cancer. High insulin levels (which follow high blood sugar levels) are linked to accelerated tumor growth.
  • Cognitive decline. Hyperinsulinemia predicts cognitive impairments in the offspring of people with dementia.

For the rest of this article, let’s get practical. Let’s answer the question: how can we measure and manage blood sugar?

How To Measure Blood Sugar

If you want to measure your blood sugar, there are four main tests:

  • Fasting Blood Glucose: Your blood sugar level after at least twelve hours of fasting.
  • Postprandial Blood Glucose: Your blood sugar level 1 to 1.5 hours after eating a meal.
  • Oral glucose tolerance test (OGTT): Your blood sugar level 2 hours after drinking 75 grams of liquid glucose.
  • Hemoglobin A1c (HbA1c): Your average blood sugar over several months. HbA1c assumes that blood cells live for three months. But since this varies from person to person, it’s an imperfect measure.

To measure fasting or postprandial blood sugar, simply use a finger-prick device at home. The Keto-Mojo meter and the Precision Xtra meter are both good options.

You can also order an at-home kit to test HbA1c. The OGTT requires a lab visit.

What’s A Healthy Blood Sugar Level?

Now that you have your blood sugar numbers, what do they mean? Let’s start with how the American Diabetes Association (ADA) classifies diabetes risk in terms of fasting blood glucose (FBG) and HbA1c:

  • Normal: FBG under 100 mg/dl, HbA1c under 5.7%
  • Prediabetes: FBG from 100 to 125 mg/dl, HbA1c from 5.7% to 6.4%
  • Diabetes: FBG over 125 mg/dl, HbA1c over 6.4%

But when you look at the data, you see that what the ADA considers normal isn’t exactly optimal.

For instance, one large study found that people with an FBG from 95-99 mg/dl were 2.33 times more likely to develop diabetes than those below 85 mg/dl. I’d say that's a pretty significant gap. There are similar data on HbA1c. In a study of over 4000 people, those at “normal” HbA1c levels (5.4-5.6%) had a higher risk of heart disease than those below 5%.

It’s also worth mentioning that insulin resistance and many of its associated problems can brew for months or years before we see blood glucose elevations. Blood glucose elevations are a sign that the system has largely tapped its ability to handle excess calories and glucose levels.

My view? Based on the science, healthy fasting blood sugar is somewhere south of 90 mg/dl and healthy HbA1c is somewhere south of 5%. There are a LOT of caveats to this. For example, some folks show fairly high fasting glucose due to the stress of the procedure or a process called Dawn Phenomena. Glucose levels in these folks look a bit scary, but then when we look at A1C, it turns out all is fine. We will dig into more of that in later articles.

6 Tips to Keep Blood Sugar Within Healthy Ranges

Most of the strategies to keep blood sugar low are also strategies to promote healthspan, and that’s no coincidence.

#1: Avoid refined carbs

When it comes to metabolic health, diet is paramount. And the Standard American Diet (SAD)—high in sugar and refined carbs—is metabolic enemy number one.

Nothing spikes blood sugar like eating simple, refined carbohydrates. I’m talking about sucrose, high fructose corn syrup (common in soda and fruit juice) cookies, crackers, and other processed garbage.

Even a moderate amount of fructose, it’s been shown, impairs insulin function. And there’s nothing moderate about the way Americans drink sugary beverages and sports drinks.

My recommendation? Eat mostly whole foods, and you’ll crave processed foods less.

I should mention, most folks get the bulk of their sodium from processed foods. Cut these out, and you’ll likely need to get your sodium (paramount for hydration) from other sources, especially if you’re eating a low-carb diet, fasting, or exercising consistently.


If you’re craving a tasty beverage but want to avoid sugar, LMNT can help you stay hydrated while pleasing your taste buds.

#2: Exercise

Exercise of all flavors can improve blood glucose regulation. When you use your muscles, you activate GLUT4 receptors in muscle cells that suck up blood sugar like a vacuum in a dusty room.

Intense exercise is a great way to activate these receptors. In one study, researchers found that just three sessions per week of high-intensity interval training (HIIT) dramatically improved insulin sensitivity in older adults.

And if you’d rather go easy, that can be beneficial too. Just one session of low-intensity weight lifting improved blood sugar regulation in type 2 diabetics.

#3: Get enough sleep

When you’re sleep-deprived, insulin function suffers. To make matters worse, you also crave more carbs as hunger hormones spiral upwards like a runaway hot air balloon.

Most people need 7-9 hours per night for optimal health. Carve out that time and guard it like a mother goose guards her eggs.

#4: Try a low-carb or keto diet

According to a 2019 consensus report published in the journal Diabetes Care, low-carb diets are the intervention with “the most evidence” for combating high blood sugar in type 2 diabetics.

My favorite piece of evidence is a study from 2018. It found that one year of supervised Keto dieting reversed type 2 diabetes (as measured by HbA1c) in 60% of 218 patients. Just as impressive: 94% of them were able to reduce or eliminate their supplemental insulin.

If you want to nerd out on this topic, check out my article on keto for type 2 diabetes.

#5: Consider intermittent fasting

Tyler Cartwright, co-founder of both LMNT and Ketogains, went deep on intermittent fasting for type 2 diabetes.

Intermittent fasting has similar metabolic effects to keto. By taking breaks from food (especially carbs) you keep blood sugar and insulin levels low. This helps stave off the insulin resistance spiral I covered earlier, but this is not via some kind of magic. IF is, first and foremost, a tool for calorie control.

Fasting can help you stay metabolically flexible, but be careful not to overdo it. Fourteen to eighteen hours seems to be the sweet spot for active folks seeking to maintain muscle, assuming they’re strength training and consuming adequate protein. Anything longer and you risk losing lean mass.

#6: Spices and supplements

A variety of foods and supplements have been shown to help with blood sugar management. These include:

  • Collagen
  • Berberine
  • Cinnamon
  • Turmeric
  • Bitter melon

Mastering Your Blood Sugar

If you want to be the master of your health, blood sugar should grab your attention. It’s a top 5 biomarker for healthy aging, so it’s definitely worth minding.

Stay in good standing by avoiding sugar, exercising, getting enough sleep, and periodically fasting. That’s how our ancestors stayed metabolically flexible, and it’s how you can too.