Your Guide to Fasting Blood Sugar Levels by Mehdi Yacoubi

Your Guide to Fasting Blood Sugar Levels
Posted on
July 18, 2021

The amount of sugar in your blood changes throughout the day. From snacks and meals to physical activity and sleep, your blood sugar levels are directly influenced by your daily habits. That's why it's important to check your fasting blood sugar levels to determine what is “normal” for your body.

Measuring your blood sugar is a simple task that requires only a continuous glucose monitor, or CGM. By implementing blood sugar tests into your daily routine, you gain access to data that provides insights into your personal health.

If you're looking to optimize your metabolism, understanding your fasting blood sugar levels is a great place to start. Let’s take a closer look at your blood sugar, why it changes, and what steps you can take to monitor and manage your blood sugar over time.

What Are Normal Fasting Blood Sugar Levels?

Your blood sugar levels are tested by measuring the amount of sugar (glucose) in your blood, either at the doctor's office or with an at-home device. This measurement is read in milligrams (mg) of glucose per deciliter (dl) of blood, abbreviated as mg/dl.

According to the American Diabetes Association (ADA), people are classified into one of three categories depending on their glucose levels: normal, prediabetic, and diabetic. When a measurement is taken after not consuming calories, it's referred to as fasting plasma glucose (FPG) or fasting blood glucose (FBG).

A normal range is considered less than 100 mg/dl after not eating (fasting) for eight hours, or less than 140 mg/dl two hours after eating. Levels ranging from 100 mg/dl to 125 mg/dl are classified as prediabetes. And those with diabetes will have fasting levels of 126 mg/dl or higher.

Even though blood glucose levels below 100 mg/dl are considered normal, it is possible for them to go too low. Readings below 70 mg/dl are usually a sign of low blood sugar, or hypoglycemia. If your blood sugar is too low, you may experience side effects such as shakiness, anxiety, sweating, or even confusion.

What Affects Blood Sugar Levels?

Fasting blood sugar levels: A man stretches outdoors with a group

Your body's systems are influenced by any number of factors both internal and external, and your blood sugar is no exception. These are the factors that will influence your blood sugar on a daily basis.


Food, or diet, will impact your blood sugar levels, as the carbohydrates in your food are used by your body for fuel. Those with diabetes will have a harder time absorbing blood sugar because the pancreas cannot produce insulin to regulate the amount of sugar in your blood. 


Physical activity will directly influence blood sugar levels, and some individuals will see changes in blood sugar levels up to 48 hours after exercise. Activity can lead to lower blood sugar levels over time as your muscles use more glucose to fuel increased energy demands.


Numerous medications exist that can involuntarily raise blood sugar. These include steroids, birth control pills, statins, cough syrup, and Niacin (a B vitamin). Other medications, such as Metformin, will lower blood sugar levels in those with high blood sugar, or hyperglycemia. Always consult your doctor when taking new medications if you have elevated blood sugar levels or if you’ve experienced elevated levels in the past.

Medical Conditions

Medical conditions, such as low levels of "good" cholesterol (HDL) or high levels of triglycerides, can increase one's risk of high blood sugar levels.

Diabetes is another medical condition that causes high blood sugar. It occurs as a result of the body's inability to produce insulin via the pancreas. Those with Type 1 diabetes cannot produce insulin to remove sugar from the blood, whereas individuals with Type 2 diabetes experience an insulin resistance within the muscles, fat, and liver.

Monitoring Your Blood Sugar Levels With a CGM

Though we often associate monitoring blood sugar levels with diabetes, this simple action should be performed by those with normal blood sugar levels too. Thanks to advancements in glucose monitoring technology, tracking your fasting blood sugar levels is easier than ever before.

A continuous glucose monitor measures blood sugar every few minutes using a sensor under the skin. A blood sample is taken, and it reads the amount of glucose in your blood, allowing you to determine if you need to make any immediate or long-term changes for your body. The latest sensor sends the information to your smartphone or smartwatch where data can be analyzed to understand trends and shifts within your body.

What Should You Do With Your Fasting Blood Sugar Readings?

Fasting blood sugar levels: A closeup of a CGM sensor on a man's arm

When it comes to optimizing your health, we recommend a three-part framework: Track, Understand, and Act.

We’ve already talked about the first step: Track. By using a CGM, you’ll not only be able to track your fasting blood sugar levels in real time, but also, you’ll get insight into what your levels are doing all day. This will give you the best picture of what’s happening inside your body.

Once you’re tracking, the next step is Understand. In addition to the blood sugar numbers themselves, take note of what you’re eating, your physical activities, and how your mood and energy change through the day. This will help you see how your blood sugar levels (and body) are reacting to the things you do. For example, you might notice that your blood sugar spikes when you eat berries or a carb-heavy meal.

The third step is Act. Now that you know how your body is responding to your daily diet and activities, you can start making changes to optimize your metabolism and keep your blood sugar balanced.

Should you find that your blood sugar readings are elevated over time, consider making a few simple changes that aim to lower your blood sugar and help you manage your levels. One such change includes drinking more water, as this helps remove excess sugar from your blood through your urine and helps you avoid dehydration. Adjustments can also be made to your diet — such as eating more whole grains, fruits, vegetables, nuts, and legumes. Lastly, consider exercising more to help your body use sugar as fuel.

If you notice consistently high blood sugar readings that aren't responding to lifestyle changes or you’re experiencing symptoms such as increased urination, thirst, and sudden weight loss or gain, you should see your healthcare provider. If left untreated, high blood sugar levels can lead to health conditions that include heart disease, high blood pressure, and a higher risk of heart attacks.

Understanding Fasting Blood Sugar Levels

Your fasting blood sugar levels will provide a detailed illustration of your body's current health status. Based on what we’ve learned, a continued focus on blood sugar levels will allow you to understand your body, what it needs, and what changes can be made through diet and exercise to optimize your personal health.

If you are looking to improve your health, boost your metabolism, or increase your longevity, continuous glucose monitoring can help. Sign up today with Vital to begin understanding your fasting blood sugar levels and receive personalized recommendations about exercise, food, and daily habits.

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