Table of Contents
Key Takeaways
Fasting blood sugar is checked after not eating for at least eight hours to help screen or track diabetes and prediabetes.
A normal fasting blood sugar is 70–99 mg/dL, while repeated readings of 126 mg/dL indicating high blood sugar and readings of lower than 70 mg/dL indicating low blood sugar.
Fasting blood sugar can be checked at home with a glucose meter, test strips, and a quick finger prick.
It’s important to track levels over time and know when to call a doctor to help manage treatment and prevent complications.
Normal fasting blood sugar levels are an important factor in looking at overall health, especially when they’re measured in the morning before eating. Testing fasting blood sugar can help individuals and their healthcare providers assess diabetes or prediabetes.
Getting an idea of these levels doesn’t have to be complex either. They can often be tested with a quick finger-prick test. For many people with diabetes, checking fasting blood sugar can be helpful for watching glucose trends and adjusting treatment as needed.
What is Fasting Blood Sugar?
Fasting blood sugar is the amount of glucose in the blood after not eating or drinking anything for at least eight hours. It’s a measure of how well the body is managing blood sugar levels in a fasted state.
The body uses glucose as an energy source by releasing insulin, a hormone that helps pull glucose into the muscles and tissues for energy. Glucose mainly comes from certain food sources, namely carbohydrates. However, without any food intake for several hours, the body works to keep glucose levels steady.
A fasting blood sugar test is often recommended by doctors and healthcare providers first thing in the morning. It’s typically used to screen for diabetes, prediabetes, and gestational diabetes.
The test is usually done as a blood draw or a finger-prick test. While finger-prick results are usually quick (within seconds), a blood draw could take hours or days to come back with a result.
What is a Normal Fasting Blood Sugar Level?
Different ranges are used to help give meaning to a person’s fasting sugar levels. Blood sugar levels that are too high could mean a person has diabetes or is at a higher risk of diabetes.
According to the American Diabetes Association (ADA), the following are the usual ranges for normal fasting blood sugar levels and prediabetes or diabetes:
70 to 99 mg/dL: Normal
100 to 125 mg/dL: Prediabetes
126 mg/dL or higher: Diabetes
Are Normal Fasting Blood Sugar Levels the Same for Everyone?
These ranges apply to most adults, but normal fasting blood sugar can vary based on the person and the protocol of the clinic or institution measuring the levels. For example, an older adult may have different goals since they may be at a higher risk of low blood sugar.
Healthy blood sugar levels should stay below 140 mg/dL two hours after eating. A reading below 70 mg/dL is considered low blood sugar and may be a medical emergency.
How to Check Fasting Blood Sugar at Home
Most people can check their fasting blood sugar levels at home. Glucose meters are a convenient way to check blood sugar at any time and don’t require complicated steps. You can buy a glucose meter with different features based on your preferences and lifestyle. These meters might include:
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You’ll also need test strips and lancets or a lancing device. However, most meters come in test kits that include everything you’ll need to start testing. Test strips are often specific to the brand of the meter.
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Steps to Check Fasting Blood Sugar
Before testing blood sugar levels, it’s important to fast for eight to 12 hours. In other words, avoid eating or drinking anything but water for this period. Most people test after waking up in the morning, before eating breakfast. Then, use the following steps as a guideline:
Wash your hands with soap and warm water
Turn on the glucose meter and insert a new test strip
Use the lancet or lancing device to prick the side of a fingertip
Gently squeeze from the base to the tip of the finger to create a small blood drop
Touch the tip of the test strip to the blood
Wait for up to 10 seconds until the results appear
Since blood glucose meters can differ, it’s best to check the instruction manual for the one you have.
Make sure to track your blood sugar trends by noting down the measurement and the time when you take it. That way, you can provide this information to your healthcare provider at your next visit.
Always keep the test strips in their original containers when not in use and check the expiration date. Rotating which finger you prick can help prevent soreness or calluses.
How to Manage High or Low Fasting Blood Sugar
If you find that your fasting blood sugar levels are higher or lower than normal, there are several things to keep in mind. What you need to do will depend on whether the levels are high (126 or higher) or low (less than 70).
High Blood Sugar
A high fasting blood sugar of 126 or higher (hyperglycemia) could mean that you have diabetes or that your current treatment isn’t working well enough if you’ve already been diagnosed. High blood sugar can be caused by the wrong medication dose, eating late at night, illness, stress, or hormonal changes. Here’s what you can do if you have high blood sugar:
Recheck your fasting levels on different mornings to see if there’s a pattern
Review nighttime snacks, alcohol intake, or missed medications
Track readings to share with your provider
Ask if medication, insulin timing, or lifestyle changes need to be changed
Low Blood Sugar
A low blood sugar level of less than 70 (hypoglycemia) usually happens in people who take too much insulin or certain diabetes medications, but it can also happen in those who skip meals or who exercise more intensely than normal without eating enough. Symptoms might include shakiness, dizziness, confusion, and headache. Here’s what you can do if you have low blood sugar:
Consume 15 grams of fast-acting carbs, such as glucose tablets, juice, or hard candies
Recheck blood sugar after 15 minutes
Avoid skipping meals, especially dinner or bedtime snacks
Talk to your healthcare provider about making a medication or dose change if lows become regular
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Know When to Consult Your Healthcare Provider
While out-of-range fasting glucose levels can happen to anyone, a pattern of lows could be more serious. It’s important to consult a healthcare provider if fasting blood sugar is out of range on a regular basis.
Call your doctor if you see any of the following:
Fasting blood sugar 126 mg/dL or higher on two or more mornings
Consistent low readings below 70 mg/dL, especially overnight or in the morning
Symptoms like confusion, fainting, severe dizziness, or trouble waking up
Blood sugar swings even while taking medications as prescribed
A serious illness, infection, or use of steroids that may affect your readings
Medical advice from a professional can help keep fasting blood sugar levels in check. They may recommend other glucose tests, like an A1c test, to see average levels over a longer period. In many cases, certain lifestyle changes, such as a balanced diet and exercise, can help maintain normal fasting blood sugar levels.
Bottom Line
Fasting blood sugar can give a tangible look at how the body is managing blood sugar. Regularly checking blood sugar can help with tracking diabetes and starting or making changes to treatment as needed. At-home tests are available to help see changes and catch problems early. If your normal fasting blood sugar gets too high or too low, a healthcare provider can help you decide what to do next.
Sources:
Blood Glucose and Insulin, American Diabetes Association (n.d.)
Prediabetes, Mayo Clinic (2023)
Diabetes Diagnosis, American Diabetes Association (n.d.)
Older Adults: Standards of Care in Diabetes—2025, American Diabetes Association (2025)
Hyperglycemia, StatPearls (2023)
Low Blood Glucose (Hypoglycemia), National Institutes of Health (2021)
FAQs
Why is fasting blood sugar checked in the morning?
Morning fasting levels show how your body controls blood sugar without food. This makes it useful for diagnosing diabetes or prediabetes and managing treatment problems.
Do I really need to fast for a full eight hours?
Yes, eating or drinking calories before testing can raise blood sugar and affect the accuracy of results. Water is fine during the fasting period.
Is one high fasting reading enough to diagnose diabetes?
No, diabetes is usually diagnosed after two or more fasting readings of 126 mg/dL or higher, or with additional tests like an A1C.
How often should I check fasting blood sugar at home?
That depends on your overall condition, medications, and healthcare provider’s instructions. Some people check daily, while others check several times a week.
