Impaired Fasting Glucose: Causes and How to Improve It

Your fasting glucose indicates the amount of sugar in your blood when you haven’t eaten for at least eight hours. Impaired fasting glucose means that this number is higher than it should be. Fasting glucose values give you a sneak peek into your metabolic status, providing valuable information about your health.

If you have impaired fasting glucose, you aren’t alone. More than 9 million adults in the United States have impaired fasting glucose. It’s a red flag that warrants a closer look into what’s happening in your body. People with impaired fasting glucose are at significant risk for developing more chronic conditions like type 2 diabetes1 or heart disease2.

But it’s not all doom and gloom if you have impaired fasting glucose. Lifestyle factors significantly impact your blood sugar. So while this condition may be a warning sign, it can also serve as an opportunity for change!

This article will explain the details about impaired fasting glucose and what you can do to optimize your numbers.

What Is Impaired Fasting Glucose?

Impaired fasting glucose3 is defined as glucose values of 100 to 125 mg/dL when you first wake up and before you’ve eaten anything for the day. Prediabetes is the same thing as impaired fasting glucose and it’s a sign that glucose is not being used efficiently in the body.

Let’s start with how things should work. The cells in our bodies rely on glucose as a primary source of energy. It powers everything from your muscles to your organs to your brain and keeps it all running smoothly.

While your liver can make small amounts of glucose, the majority comes from carbohydrate-rich foods like fruits, veggies, grains, treats, and starches. Carbs are eventually broken down into glucose, which travels throughout your body in your bloodstream. Whatever isn’t used by the cells for energy is stored in your liver, muscles, or fat cells.

Regulating glucose is critical—your body carefully monitors how much stays in your blood versus how much is taken in by your cells. When glucose rises, insulin is released from your pancreas.

Insulin is the hormone that signals that it’s time to get sugar out of the blood. Once it moves into your cells, your blood sugar drops, and insulin should decrease as well.

Ideally, your glucose should stay low while you sleep, but as it gets closer to morning, blood sugar can rise slightly as part of a normal wakening response. This is known as the dawn phenomenon.

The dawn phenomenon is the body’s way of preparing for the day by releasing hormones that signal the release of glucose from your liver. At the same time, insulin sends the signal to move glucose out of the blood and into the cells to give you energy to get up. This is a normal response, and the rise should be temporary until insulin does its job.

With impaired fasting glucose, your body doesn’t process glucose normally. Instead, your morning blood sugar remains high.

What Causes Impaired Fasting Glucose?

Impaired fasting glucose happens for two main reasons:

Your body doesn’t make enough insulin
Your cells aren’t responding to insulin as they should (called insulin resistance).

While there can be multiple root causes, impaired fasting glucose is linked to several risk factors4, including:

Sedentary lifestyle
Over the age of 45
Overweight or obesity
Family history of type 2 diabetes
Gestational diabetes
PCOS
High blood pressure or high cholesterol
Certain ethnicities, including African American, American Indian, Asian American, Latinx
Sleep apnea

But here’s the good news: Even if you can’t change risk factors like your ethnicity or family history, many of these are modifiable. Your lifestyle choices and habits can go a long way to supporting healthy blood sugar.

How Do You Test and Diagnose Impaired Fasting Glucose?

Testing for impaired fasting glucose is a simple blood test. It’s usually part of a routine physical with other blood tests. You need to fast for at least eight hours before getting tested, including avoiding that morning cup of coffee with cream or collagen.

And while 100 mg/dL or below is technically considered normal, anything above 90 mg/dL is still creeping up close to that cut-off. Ideally, your fasting values should be 72-90 mg/dL for optimal health.

Does Impaired Fasting Glucose Have Any Symptoms?

Impaired fasting glucose has no symptoms. Without testing, you can go for years without a diagnosis. Aside from increasing your risk for diabetes, impaired fasting glucose can impact other areas of health and make it more challenging to lose weight (as you will learn below).

Does Impaired Fasting Glucose Make it Harder to Lose Weight?

The short answer is yes, elevated glucose can make it more challenging to maintain a healthy weight. The relationship is complex and related to insulin.

As noted above, insulin rises in response to increased blood sugar. This is a healthy, normal physiological response so you can maintain normal glucose levels in your blood.

But on the flip side, if your cells aren't responding as they should, your body will continue trying to find balance by releasing more and more insulin. Over time, excess exposure to insulin can make it harder to lose weight.

Insulin is considered an anabolic or growth hormone. Aside from stimulating your fat cells to take in glucose, it contributes to fat storage by making it more difficult for your body to break down stored fat (lipolysis).

In normal conditions, lipolysis is turned on to give your body an alternative source of energy5 when you are fasting or don't have quick access to glucose in the blood. Once you start eating again, the release of insulin inhibits lipolysis because you now have glucose for energy.

This process isn't a problem for people with a normal glucose response because insulin is only in the blood short-term. However, chronic exposure to higher than average amounts of insulin can be a problem for people with blood sugar dysregulation. Essentially, insulin shuts down the metabolic pathways6 that promote cellular clean-up and fat burning.

People with impaired fasting glucose also produce more insulin at bedtime to decrease their blood sugar. Sleep is usually a time for repair, restoration, and fat burning (because you’re fasting). But, those with IFG have higher insulin levels, which promotes the building and storage of fat instead of breaking it down.

What’s the Difference Between Impaired Fasting Glucose and Prediabetes or Diabetes?

Impaired fasting glucose and prediabetes are the same thing. Both mean that your body is not handling glucose efficiently. But diabetes is a more serious diagnosis.

The following are the ranges for prediabetes and diabetes7 based on fasting glucose:

Normal: less than 100 mg/dL
Prediabetes: 100 mg/dL to 125 mg/dL
Diabetes: 126 mg/dL and above

All three conditions share the same foundational principle that something happens in the body to interrupt the normal regulation of glucose and insulin.

People with diabetes often need medications in addition to lifestyle changes to help manage their blood sugar. However, people with impaired fasting glucose can still reverse progression.

Does Impaired Fasting Glucose Mean You’ll Get Diabetes?

Prediabetes or impaired fasting glucose is like a check-engine light going off in your car. You wouldn’t ignore your car’s warning light and keep driving until it breaks down. If you have impaired fasting glucose, you can get the car back on the road with lifestyle changes.

On the other hand, if you have impaired fasting glucose and don’t pay attention, it’s much more likely that you will progress to diabetes. Your cells can lose sensitivity to insulin, and in some cases, your pancreas will just give up and make less. This is what happens to people with diabetes who need to rely on outside sources of insulin or medications that stimulate the pancreas to make more insulin.

It’s also helpful to note that some of the same health risks associated with diabetes are seen with impaired fasting glucose. The association between diabetes and heart disease is well known, but having impaired glucose, especially in women, may be just as risky.

The Framingham Heart Study8, a notable long-term research project, found that women with impaired fasting glucose have similar heart disease risks as women with diabetes. The same results weren’t seen for men, but it does show how critical it is to work on blood sugar control, even if you don’t have diabetes and are otherwise healthy.

What’s the Connection Between Impaired Fasting Glucose and Insulin Resistance?

In some cases, impaired fasting glucose can be related to insulin resistance9, but not always. It can be a combination of insulin resistance or that your body just isn’t making enough insulin to regulate blood sugar.

Insulin resistance means that while your pancreas releases insulin, your cells ignore the signal. Glucose stays in your blood and remains high. It’s like insulin keeps calling, but no one answers.

It’s a vicious cycle because your body will keep pumping out more and more insulin to find equilibrium. Sometimes the cells will eventually wake up and answer the phone, but it takes more insulin to keep the phone ringing. But other times, the pancreas will just give in and hang up, and insulin production drops off completely.

How Can You Improve Your Fasting Glucose?

Lifestyle habits are incredibly effective for regulating blood sugar. A well-known program called the Diabetes Prevention Program10 (DPP) has been used all over the country for people with prediabetes and impaired fasting glucose. Studies show that people who follow the suggested lifestyle modification program reduce their risk of progression to diabetes, even compared to people who rely on medications.

Impaired fasting glucose is a wake-up call. It’s information you can use to motivate you to make changes. Here are some of the ways you can improve fasting glucose:

1. Maintain a healthy weight

Excess body fat doesn’t just impact our blood sugar. It also puts us at risk for many other chronic diseases. But you don’t have to starve yourself to see results. Even losing 10 percent of your body weight can significantly improve blood sugar.

2. Minimize simple and processed carbs

Simple carbs like sugar, soda, juice, bread, or pasta quickly spike your blood sugar and are filled with empty calories that provide minimal (if any) nutritional value. Although we all respond to carbs differently, complex carbs from veggies, fruits, or whole grains like oats or quinoa don’t spike your blood sugar in the same way because they are also high in fiber, which takes longer to digest.

3. Avoid high-carb foods at night

Eating too many carbs right before you go to bed means your body must work to stabilize your blood sugar right when you’re winding down. If you have impaired fasting blood sugar, try eating more protein and fat with small amounts of complex carbs before bed.

4. Bump up your physical activity

Exercise helps make your cells more sensitive to insulin while adding lean body mass. Lean body mass boosts metabolism, so it increases how many calories you burn while at rest. Studies on healthy people have found that exercise can improve insulin sensitivity and glycemic control11, particularly in those who exercise in a fasted state. Plus, it’s an instant mood enhancer and stress buster.

5. Get enough sleep

The amount of rest you get overnight is closely linked to your fasting glucose and blood sugar response throughout the day. Sleep deprivation is associated with increases in stress hormones like cortisol that can raise your blood sugar and negatively impact insulin sensitivity12. Plus, lack of sleep is associated with many other health concerns, including cardiovascular disease, depression, and weight gain13. Aim for 7 to 8 hours each night for optimal rest and recovery.

Impaired Fasting Glucose Summed Up

In the end, it’s helpful to remember that small changes add up to big results. Elevated fasting blood sugar may be a warning sign from your body that something needs attention, but there are plenty of things you can do.

If you need to make changes, start with one new action and keep adding on until they are part of your daily routine. Whether it’s focusing on your sleep, diet, or meal patterns, all of these habits support better blood sugar balance and optimal long-term health.

FAQ About Impaired Fasting Glucose

What are the differences between impaired glucose tolerance and impaired fasting glucose?

Impaired glucose tolerance refers to alterations in your blood sugar response after eating. Impaired fasting glucose refers only to the measure of blood sugar when you’ve gone at least eight hours without eating. Both are essential markers for glucose metabolism and may increase your risk for developing diabetes.

What is impaired fasting glucose during pregnancy?

Impaired fasting glucose happens in pregnancy because the placenta releases hormones that affect how your body uses insulin. Checking fasting glucose is part of standard labs during pregnancy, but the glucose tolerance test is how it’s diagnosed. Getting your glucose in check during pregnancy is especially important because high blood sugar increases the risk of complications for mom and baby.