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Jan. 12, 2026

Is fasting good for prediabetes?

Patricia Castaneda, PA

Medically reviewed by:
Patricia Castaneda, PA

One of the health trends that may have an impact on prediabetes is fasting. You may have heard about fasting and how it can affect your health.

Prediabetes is a significant health threat for Americans today. In fact, experts estimate that as many as 98 million American adults currently have prediabetes.1 Without intervention, prediabetes can turn into type 2 diabetes—a chronic condition that can have devastating health consequences. These consequences include blindness, nerve pain, amputation and severe infections. This is why health professionals are interested in finding ways to manage and even reverse prediabetes.

Read on to learn more about the growing interest in fasting and how it can impact your health if you have prediabetes.

Understanding prediabetes

To understand the role of fasting in prediabetes, it’s important first to understand prediabetes. Prediabetes is a condition of above-normal blood glucose. While blood glucose levels are abnormal in prediabetes, they are not high enough to be officially labeled as type 2 diabetes. Prediabetes can indicate a developing problem that can be reversed. You can consider prediabetes as a critical warning sign that diabetes might not be too far on the horizon.

Prediabetes can happen if your body is developing resistance to the hormone insulin. To determine whether you have prediabetes, health professionals can look at various blood tests.

Blood tests for prediabetes

Three main blood tests can be used to assess for prediabetes.

  • Fasting blood sugar level: This is a blood test that measures the glucose (sugar) level in your blood after you’ve fasted for a specific length of time. In prediabetes, your fasting blood sugar level is between 100 and 125 mg/dL.
  • 2-hour post-glucose challenge test: A blood test that measures blood glucose (sugar) at a fixed interval after consuming a standard glucose drink. In prediabetes, your 2-hour post-glucose challenge test is between 140-199 mg/dL.
  • Hemoglobin A1C test (HbA1C or simply A1C): This can also be used to define prediabetes, as it measures your average blood sugar level over the past 8 to 12 weeks. Having an HbA1C level of between 5.7% and 6.4% also means you have prediabetes.2

How blood sugar regulation works

The hormone insulin is very important for blood sugar regulation. Typically, when you eat a meal, your digestive system breaks down food into small parts. Carbohydrates break down into smaller glucose molecules. These glucose molecules travel from your digestive system into your bloodstream. The bloodstream helps deliver glucose to the cells in your body that use glucose as energy. However, these cells need help pulling the glucose molecules from the bloodstream into their cell bodies for use. This is where the hormone insulin comes into play. The pancreas makes insulin. It helps transport glucose from the bloodstream into cells.

In prediabetes and diabetes, your cells become less responsive to insulin. This is known as insulin resistance, or decreased insulin sensitivity. Insulin resistance means that less sugar gets pulled into cells, and more sugar remains in the bloodstream. Your pancreas can try to create more insulin to try to make up for the increased sugar levels, but it often can’t keep up. Over time, elevated blood sugar levels can cause damage to your body’s small blood vessels and nerves. This can result in severe health consequences, such as blindness, nerve pain, amputations and severe infections.

Why lifestyle changes are critical in prediabetes

The good news about abnormal blood sugar regulation in prediabetes is that it can be reversed. Lifestyle changes—like changing your diet, exercising more and even fasting—can reverse the body’s insulin resistance.3 These lifestyle changes can help lower abnormal glucose levels and positively impact how your body uses the hormone insulin.

What is fasting?

Put simply, fasting refers to any period of time during which you are not eating food. You generally fast at least once a day while sleeping. For example, if you finish eating dinner at 7 pm and eat breakfast at 7 am, you are naturally fasting for 12 hours overnight.

During fasting, your body turns to other sources of energy aside from the quick release of sugar into the bloodstream. During a fasting state, your cells can use glucose from other stores, such as the muscle cells and liver. These stores are known as glycogen. Sometimes, alternative energy sources, such as fat, can be used for energy as well. When you are fasting, your body’s natural processes are not devoted purely to the breakdown and digestion of food. Other processes, such as cellular repair, get more attention.

When people talk about fasting, they define it as more intentional periods of going without food. Fasting comes in different forms. Each form introduces a period of time without eating. Some are longer than others.

Different types of fasting:

  • Intermittent fasting: This is a type of fasting where you have defined periods of time when you are eating a low number of calories or no calories. At other times, you are eating your normal amount of calories. Examples of this include 5:2 fasting, in which you eat a low number of calories for 2 days in a row, then eat a normal amount of calories for 5 days. Other types of fasting include alternate-day fasting, in which you switch off every day between normal caloric intake and reduced caloric intake.
  • Time-restricted fasting: This type of fasting essentially extends your regular overnight fast each day. It establishes a fixed time window, usually between 6 and 10 hours each day, in which you eat your daily food. The rest of the day, you are fasting. This can benefit your metabolic health in prediabetes. For example, recent research shows that eating meals early in the day, within the first 6 to 8 hours, can reduce blood sugar spikes throughout the day.4
  • Prolonged fasting: This typically refers to fasting for a long period of time, 24 hours or more at a time. This type of fasting can promote weight loss, which can improve metabolic health.

How fasting affects metabolism

Fasting can positively affect your metabolism because it can help stabilize your blood sugar levels. When you are not eating frequently throughout the day, your blood sugar does not have dramatic spikes and dips.5 Instead, fasting can help lower your overall blood glucose and keep your blood sugar levels more steady. Since fasting can also lead to the breakdown of glucose stores and fat, it can lead to weight loss. Weight loss can help reduce your chances of developing diabetes, and it can even help reverse prediabetes.

Potential benefits of fasting for prediabetes

Fasting can help keep blood sugars from large spikes and valleys. Health professionals call this phenomenon improved glycemic control. In this way, fasting can improve insulin sensitivity. Researchers have found that certain forms of fasting can lower hemoglobin A1c (HbA1C), which helps improve prediabetes.6 Fasting can also help you lose weight. Weight loss alone can improve blood sugar levels and reduce insulin resistance. These effects may reverse prediabetes for some people.

Risks and considerations with fasting

Fasting can be a helpful tool in managing prediabetes. However, fasting is not an appropriate tool for everyone. If you have certain medical conditions, like heart or kidney problems, insulin-dependent diabetes or pregnancy, fasting may not be advisable. Fasting can cause side effects such as dangerously low blood sugar, low blood pressure or nutrient deficiencies. It’s important to discuss with your physician whether fasting is right for you.

Practical tips for safe fasting

If you have decided to try fasting, it’s essential to do so safely. Here are some helpful tips for safe fasting:

  • Start gradually. To give your body a chance to adjust to being in a fasting state more frequently, start gradually. You can try to extend your natural overnight fast by an hour or two, and stay like this for a week to adjust. Or introduce a day of lower-than-normal calories just once a week, then increase to twice a week or to alternate days.
  • Pay attention to nutrition. It’s important to give your body the balanced nutrition it needs during the time that you are not fasting. This means following a healthy diet of fruits, vegetables, whole grains, healthy fats and lean proteins. This will ensure that your body is taking in high-quality nutrients, and you are more likely to feel full for longer.
  • Monitor blood sugar during fasting. If you are in the habit of checking your blood sugar, it’s a good exercise to continue doing so when fasting. This can help you track how you feel at different blood sugar levels. It can also help you recognize a condition of dangerously low blood sugar, known as hypoglycemia.
  • Stay well-hydrated. It’s important to drink lots of water while fasting. This can help you avoid certain side effects, such as muscle cramps or headaches that can come from feeling hungry.7

Alternatives to fasting

It’s important to know that fasting is only one method of improving blood sugar control in prediabetes. If fasting is not appropriate for your lifestyle, there are other ways to lose weight and improve glycemic control. These include:

  • Reducing your intake of highly processed carbohydrates and added sugar
  • Increasing physical activity
  • Reducing sedentary behavior
  • Improving sleep hygiene

The bottom line: Is fasting good for prediabetes?

When carried out under the guidance of a medical professional, fasting can be a very effective tool. Fasting can help improve your glucose metabolism by reducing blood sugar fluctuations. It can also help you lose weight, which can have an independent benefit in prediabetes. Yet, fasting is not a one-size-fits-all solution for everyone with prediabetes. Fasting may not be appropriate for you if you have certain medical conditions or take certain medications. In these cases, some alternative lifestyle measures can help you manage or even reverse your prediabetes.

If you are interested in learning more about fasting’s effect on prediabetes, it’s important to get evaluated by your primary physician. Your doctor can help pinpoint your current state of glucose regulation. Then they can help you develop a plan to improve your glycemic control, including fasting. To learn more about prediabetes and to get support in managing your blood sugar levels, get in touch with WellMed today.

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