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Understanding Fasting Blood Sugar Levels: Normal Range and Test

Last updated on : 28 Feb, 2025

Read time : 8 min

Fasting blood sugar levels are a crucial indicator of your body’s ability to regulate glucose and maintain overall metabolic health. By understanding what fasting blood sugar is, its normal range, and how the test is conducted, you can gain valuable insights into your well-being and effectively manage conditions like diabetes. In this blog, we will explore these key aspects of fasting blood sugar to help you stay informed and proactive about your health.

What is Fasting Blood Sugar?

Fasting blood sugar, also referred to as fasting blood glucose, is a measurement of the glucose concentration in your blood after you have abstained from consuming any food or beverages (except water) for a period of 8 to 12 hours. This test is usually conducted in the morning, before having breakfast, and is commonly used to diagnose conditions such as prediabetes, diabetes, and gestational diabetes. By assessing your blood sugar levels in a fasted state, healthcare providers can gain a clearer understanding of how your body manages glucose in the absence of recent food intake.

Normal Range of Fasting Blood Sugar

Knowing the normal range of fasting blood sugar is essential for assessing your metabolic health and identifying potential issues. Here are some key points to keep in mind:

  • A normal fasting blood glucose level typically falls between 70 to 99 mg/dL (3.9 to 5.5 mmol/L).
  • If your fasting blood sugar is between 100 and 125 mg/dL (5.6 to 6.9 mmol/L), it may indicate impaired fasting glucose, which is a form of prediabetes.
  • Fasting blood sugar levels at or above 126 mg/dL (7 mmol/L) are often indicative of diabetes.
  • It’s important to note that these values may vary slightly among different laboratories, so it’s always best to consult with your doctor for personalised interpretation of your test results.

Why is Fasting Blood Sugar Important?

Fasting blood sugar is a key indicator of your metabolic health and plays a crucial role in managing diabetes. Here are some reasons why fasting blood sugar is important:

  • It helps assess how well your body manages glucose between meals, reflecting your body’s ability to produce and respond to insulin.
  • Elevated fasting blood sugar levels are linked to insulin resistance, diabetes, and increased risk of heart disease, kidney disease, and other metabolic disorders.
  • High fasting glucose can lead to the formation of advanced glycation end products (AGEs), which can damage blood vessels and contribute to oxidative stress and inflammation, affecting your overall health and quality of life.
Do you know that fasting blood sugar not only reflects glucose levels but also provides insights into metabolic health, insulin resistance, cardiovascular risk, liver function, hormonal balance, and stress levels? Maintaining normal blood sugar is achievable through a healthy diet and an active lifestyle.

Factors Affecting Fasting Blood Sugar Levels

Various factors can impact your fasting blood sugar levels, affecting how your body regulates glucose. Let’s explore some of these factors in more detail.

1. Diet

The food you eat plays a significant role in maintaining normal fasting blood sugar levels. A healthy diet rich in fibre, whole grains, and high-protein foods can help regulate blood sugar. Choosing whole grain bread and pasta over white varieties, limiting sugar and salt intake, and incorporating nonstarchy vegetables into your meals are all beneficial strategies for managing fasting blood sugar.

2. Lifestyle

Your lifestyle habits can also influence your fasting blood sugar levels. Regular exercise, such as walking, swimming, or cycling, can increase insulin sensitivity and help lower fasting blood sugar by promoting muscle glycogen storage. Getting adequate sleep (7-8 hours per night) and practising stress-reducing techniques are also essential for maintaining healthy glucose levels.

3. Medications and Illnesses

Certain medications and health conditions can significantly affect fasting blood sugar levels. Some diabetes medications, if not properly adjusted, can cause blood sugar to drop too low. On the other hand, conditions like gum disease and hormonal imbalances can lead to elevated blood sugar levels. Additionally, stress hormones released during illness or chronic stress can cause a rise in fasting glucose levels.

How to Test Fasting Blood Sugar Levels?

A simple and commonly used test is employed to determine your fasting blood sugar levels:

  • Preparation: Fast for 8 to 12 hours before the test, consuming only water if necessary.
  • Procedure: A healthcare provider will take a blood sample from a vein in your arm or use a finger prick to collect blood.
  • Testing Location: The test can be conducted in a doctor’s office, lab, or hospital.
  • Measurement: The blood sample is sent to a lab for testing, or it can be measured immediately using a blood glucose monitor and test strip.
  • Results: The results are usually available quickly, within hours or days, indicating your blood glucose level in mg/dL.

Causes of Abnormal Fasting Blood Sugar Levels

Abnormal fasting blood sugar levels can be caused by various factors, including health conditions and other medical issues.

High Fasting Blood Sugar

High fasting blood sugar levels (126 mg/dL or higher) indicate diabetes, often resulting from inadequate insulin production or insulin resistance. Other causes include pancreas difficulties, endocrine disorders like Cushing syndrome, certain medications, and gestational diabetes during pregnancy. On the other hand, low fasting blood sugar levels can also be a cause for concern.

Low Fasting Blood Sugar

Low fasting blood sugar levels (below 70 mg/dL) can be due to diabetes medications lowering blood sugar too much, other medications, or conditions such as hypoglycemia. It may also result from excessive insulin dosing or delayed meals.
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Tips to Maintain Healthy Fasting Blood Sugar Levels

Adopting a healthy lifestyle is essential for maintaining optimal fasting blood sugar levels. Here are some practical tips to help you keep your blood sugar in check:

  • Consume a well-balanced diet rich in fibre, whole grains, and lean proteins to promote stable blood sugar levels
  • Minimise your intake of sugary and salty foods to prevent sudden spikes in blood glucose
  • Stay well-hydrated by drinking ample water and avoiding sugary beverages
  • Engage in regular physical activity to improve insulin sensitivity and regulate blood sugar
  • Practice stress management techniques like meditation or yoga to keep stress-induced blood sugar fluctuations at bay
  • If you are on diabetes medication, follow your doctor’s instructions carefully to prevent hypo- or hyperglycemia

Risks of Uncontrolled Fasting Blood Sugar

Failing to maintain healthy fasting blood sugar levels can put you at risk for various complications. Some of the potential risks include:

  • Damage to blood vessels, nerves, and vital organs, increasing the likelihood of heart disease, stroke, kidney failure, and vision problems
  • Life-threatening diabetic emergencies such as diabetic ketoacidosis (DKA) in type 1 diabetes or hyperosmolar hyperglycemic state (HHS) in type 2 diabetes
  • Increased risk of developing chronic conditions like hypertension, obesity, and other metabolic disorders
  • Reduced quality of life due to frequent hospitalisations, impaired mobility, and overall decreased well-being

When to Contact a Doctor

If you experience any of the following, it is important to reach out to your doctor promptly:

  • Consistently high blood sugar levels, i.e., above 130 mg/dL when fasting or above 180 mg/dL after meals
  • Symptoms of hyperglycemia, such as excessive thirst, frequent urination, or blurred vision
  • Episodes of hypoglycemia caused by low blood sugar

Conclusion

Maintaining fasting blood sugar levels within the normal range is crucial for preventing diabetes-related complications and ensuring overall well-being. By adopting a healthy lifestyle that includes a balanced diet, regular exercise, and adherence to prescribed medication, you can effectively manage your blood sugar levels. Regular monitoring and timely medical intervention, when necessary, are key to maintaining optimal health and preventing the risks associated with uncontrolled fasting blood sugar.

FAQs

What is the normal range of fasting blood sugar?

70-100 mg/dL is the normal fasting blood sugar range for healthy individuals.

Is a fasting blood sugar level of 117 mg/dL bad?

Yes, 117 mg/dL falls in the prediabetes range (100-125 mg/dL).

What is the danger level of fasting blood sugar?

126 mg/dL or higher indicates diabetes and requires medical attention.

What is a good non-fasting blood sugar level?

Below 140 mg/dL for healthy individuals and under 180 mg/dL for diabetics.

How many hours of fasting are required for a blood sugar test?

An 8-12 hour fast is required for accurate results.

What if my fasting blood sugar is 200 mg/dL?

A level of 200 mg/dL indicates uncontrolled diabetes and needs urgent care.

How can I reduce my blood sugar level immediately?

Stay hydrated, eat fibre-rich foods, avoid sugar, and follow medical advice.

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Our healthcare experts have carefully reviewed and compiled the information presented here to ensure accuracy and trustworthiness. It is important to note that this information serves as a general overview of the topic and is for informational purposes only. It is not intended to diagnose, prevent, or cure any health problem. This page does not establish a doctor-patient relationship, nor does it replace the advice or consultation of a registered medical practitioner. We recommend seeking guidance from your registered medical practitioner for any questions or concerns regarding your medical condition.

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