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 diabetes<sup>1</sup> or heart disease<sup>2</sup>.
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 glucose<sup>3</sup> 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.
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 also decrease.
Ideally, your glucose should stay low while you sleep, but as it gets closer to morning, your blood glucose levels 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 the energy to get up. This is a normal response, and the rise should be temporary until insulin does its job.
With impaired fasting blood glucose, your body doesn’t process glucose normally. Potential signals of impaired fasting glucose and high blood sugar (hyperglycemia) include, but are not limited to:
- Changes in vision: High blood sugar levels can cause the eye's lens to swell, making it more difficult to focus an image.
- Increased need to urinate: When excess glucose is excreted in the urine, it pulls water to balance glucose and water. This causes more frequent urination that results from excess glucose in the urine.
- Increased thirst: When you excrete excess glucose and water in the urine, your body becomes dehydrated, and you are thirsty. Increased thirst is to compensate for fluids lost from increased urination.
- Fatigue: When body cells do not get enough glucose for energy, it can cause fatigue.
- Weight loss: Calories are lost when glucose is lost in the urine. High blood sugar also indicates insulin resistance, which means body cells cannot access glucose for energy, so they break down body fat for energy instead.
What Causes Impaired Fasting Glucose?
Impaired fasting blood 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 factors<sup>4</sup>, including:
- Sedentary lifestyle
- Over the age of 45
- Overweight or obesity
- Family history of type 2 diabetes
- Gestational diabetes
- High blood pressure or high cholesterol
- Certain ethnicities, including African American, American Indian, Asian American, Latinx
- Sleep apnea
But here’s the good news: Many of these are modifiable even if you can’t change risk factors like your ethnicity or family history. Your lifestyle choices and habits can go a long way to supporting healthy blood sugar.
IFG Diagnosis and Treatment
Testing for impaired fasting glucose is a simple blood test. It’s usually part of a routine physical and could accompany other blood tests. You must fast for at least eight hours before performing the test.
While 100 mg/dL or below is technically considered normal, anything above 90 mg/dL still creeps up close to that cut-off. Ideally, your fasting values should be 72-90 mg/dL for optimal health.
Impaired Fasting Glucose vs. Prediabetes vs. 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.
- 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 and lifestyle changes to help manage their blood sugar. However, people with impaired fasting glucose can still reverse progression.
What’s the Connection Between Impaired Fasting Glucose and Insulin Resistance?
In some cases, impaired fasting glucose can be related to insulin resistance<sup>9</sup>, but not always. It can be a combination of insulin resistance or your body 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 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.
A Memo: Why Stable Blood Sugar
Lifestyle habits are incredibly effective for regulating blood sugar. A well-known program called the Diabetes Prevention Program<sup>10</sup> (DPP) has been used nationwide 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, increasing how many calories you burn while at rest. Studies on healthy people have found that exercise can improve insulin sensitivity and glycemic control<sup>11</sup>, particularly in those who exercise in a fasted state. Plus, it’s an instant mood enhancer and stress buster.
5. Get enough sleep
The rest you get overnight is closely linked to your fasting glucose and blood sugar response throughout the day. Sleep deprivation is associated with increased stress hormones like cortisol that can raise your blood sugar and negatively impact insulin sensitivity<sup>12</sup>. Plus, lack of sleep is associated with many other health concerns, including cardiovascular disease, depression, and weight gain<sup>13</sup>. Aim for 7 to 8 hours each night for optimal rest and recovery.
6. Limit alcohol
When you drink, a small amount of alcohol is absorbed in the stomach, but the majority of the absorption occurs in the small intestine. Once absorbed, alcohol moves to your liver, where it is processed with the help of specialized enzymes that break it down to remove it from the body.
The liver helps regular blood sugar by releasing stored glucose into the bloodstream when you need an energy source. Alcohol inhibits this process because the liver prioritizes metabolizing the alcohol<sup>14</sup> before anything else. As a result, your blood sugar drops. In fact, gluconeogenesis can drop by almost half after four drinks.<sup>15</sup>
Interestingly, alcohol can also temporarily increase insulin sensitivity<sup>16</sup>, which can also lower blood sugar as the body pulls more glucose out of the blood.
7. Avoid smoking
Tobacco use can increase blood pressure by damaging the inner lining of blood vessels and by stimulating the sympathetic nervous system. Smoking stiffens blood vessels, which increases resistance and raises blood pressure. In one study, researchers found that smoking even a single cigarette increases blood vessel stiffness in both smokers and nonsmokers.<sup>17</sup> Smoking increases the risk of heart disease secondary to high blood pressure by two to three times. However, this risk decreases within two to three years if you stop smoking!<sup>18</sup>
Nicotine can also induce insulin resistance. While cigarette smokers may be less sensitive to insulin while smoking, their insulin sensitivity increases within one to two weeks after they stop smoking.
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 of 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 checked during pregnancy is especially important because high blood sugar increases the risk of complications for mom and baby.
Can you reverse impaired fasting glucose?
Yes, impaired fasting glucose can be reversed. By adopting some of the lifestyle changes that were mentioned in this article, you can lose weight, lower your blood sugar levels, and prevent diabetes from developing.
How does impaired fasting glucose affect your health?
Impaired fasting glucose is a type of prediabetes, and individuals living with this condition are at an increased risk of depression, anxiety, and other mental health challenges.19 However, this condition should be closely monitored as it could worsen and escalate into diabetes. It is crucial to place importance on exercise and eating a balanced diet to mitigate the symptoms of prediabetes and reduce the risk of developing diabetes in the future.
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Topics discussed in this article:
- Mahmud A, Feely J. Effect of smoking on arterial stiffness and pulse pressure amplification. Hypertension. Jan 2003;41(1):183-7. doi:10.1161/01.hyp.0000047464.66901.60
- Rehill N, Beck CR, Yeo KR, Yeo WW. The effect of chronic tobacco smoking on arterial stiffness. Br J Clin Pharmacol. Jun 2006;61(6):767-73. doi:10.1111/j.1365-2125.2006.02630.x
- Deschênes SS, Burns RJ, Graham E, et al. Prediabetes, depressive and anxiety symptoms, and risk of type 2 diabetes: a community-based cohort study. J Psychosom Res. 2016;89:85-90. doi:10.1016/j.jpsychores.2016.08.011