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Metabolic health

Glucose

Also known as: Blood sugar test, Blood glucose test, Fasting blood glucose (FBG), Random glucose test, Oral glucose tolerance test (OGTT)

Glucose is the body’s main source of fuel. When you eat, carbohydrates break down into glucose, which enters the bloodstream. The hormone insulin helps move glucose into cells for energy, while the hormone glucagon raises glucose when levels dip.

A glucose test measures the concentration of glucose in the blood. It’s one of the most common and important blood tests because abnormal levels can signal diabetes, prediabetes, hypoglycemia, or other metabolic issues. Because abnormal blood sugar can cause immediate symptoms (like shakiness or confusion) and long-term complications (like heart disease or kidney damage), timely testing and follow-up care are critical.

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Key takeaways

  • Sample required: Blood, usually from a vein or a finger stick

  • Tests for: Measures blood sugar to help evaluate for diabetes, prediabetes, hypoglycemia, and other metabolic conditions.

  • Healthy range: Normal fasting glucose range is between 70 and 100 milligrams per deciliter (mg/dL)

What can a glucose test tell you?

Glucose testing provides insights into how well your body regulates sugar and energy. It can help:

  • Diagnose diabetes or prediabetes. Your healthcare provider may order fasting or random glucose tests if diabetes is suspected. Persistently high results, confirmed on a separate day or alongside symptoms, can indicate prediabetes or diabetes. 

  • Monitor treatment. People with diabetes often check their glucose levels daily and through lab testing to track therapy effectiveness.

  • Detect hypoglycemia. Low glucose levels can explain symptoms like dizziness, sweating, and palpitations.

  • Screen at-risk populations. Testing is used in routine care and for people on certain medications that can raise blood sugar, including steroids.

What is being tested?

Glucose is a simple sugar and the body’s preferred energy source. A glucose test can detect: 

  • Too much glucose (hyperglycemia), which can damage blood vessels and organs, increasing the risk of cardiovascular disease, kidney failure, and vision problems.

  • Too little glucose (hypoglycemia), which can deprive the brain and muscles of energy, leading to confusion, seizures, or loss of consciousness.

Because glucose levels shift throughout the day, providers select different tests—such as fasting, random, glucose tolerance, or hemoglobin A1C—based on whether they need a short-term or long-term picture of blood-sugar control..

Where is the glucose test typically included?

A provider may order a stand-alone glucose test if symptoms suggest high or low blood sugar. Glucose tests are also commonly included in the following panels:

  • Basic metabolic panel (BMP). Evaluates blood sugar, electrolytes, and kidney function

  • Comprehensive metabolic panel (CMP). Adds liver function measures to the BMP

  • Screening protocols. Used in preventive care to detect diabetes and prediabetes

Who should get a lucose test?

Providers may recommend glucose testing if you:

  • Have diabetes risk factors: Age 35 or older who have overweight, obesity, a family history of diabetes, limited physical activity, or related conditions such as high blood pressure, PCOS, or high triglycerides.

  • Have symptoms of hyperglycemia: Increased urination (polyuria), thirst (polydipsia), hunger (polyphagia), blurred vision, fatigue, or frequent infections

  • Have symptoms of hypoglycemia: Shakiness, sweating, palpitations, irritability, or confusion.

  • Take medications that affect blood sugar: Steroids, beta blockers, or diabetes medications.

How Labs by Hers works

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    Book your test

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  • 2

    Get your results

    Review your lab results to understand which areas of your health may need attention.

  • 3

    Spot early signals

    Identify potential health risks or system imbalances before they become more serious.

  • 4

    Get your action plan

    Receive expert guidance tailored to your health profile and test results.

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    Improve over time

    Track your progress through a mid-year panel and ongoing provider check-ins.

Not available in all 50 states. Eligibility and provider order required. Lab results alone are not intended to diagnose, treat, or cure any condition. A provider will reach out about critical results and plans include access to 24/7 provider messaging.

Images for illustrative purposes only.

Frequently asked questions

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What causes changes in glucose levels? 

Glucose levels can rise or fall for many reasons related to diet, hormones, medications, or underlying health conditions. High glucose, known as hyperglycemia, is most often linked to diabetes (type 1 or type 2), but it can also occur with steroid use, other medications, acute stress or illness, endocrine disorders like Cushing’s syndrome, or periods of inactivity combined with high-carbohydrate meals.

Low glucose, or hypoglycemia, is frequently caused by diabetes medications such as insulin or sulfonylureas, but it can also result from prolonged fasting, excessive alcohol use, hormonal deficiencies affecting the adrenal or pituitary glands, or severe liver or kidney disease. In rare cases, an insulin-secreting tumor (insulinoma) can lead to persistently low glucose. Because glucose levels fluctuate throughout the day and can be influenced by food, stress, and activity, providers typically interpret results alongside medical history and other lab findings to determine the cause.

What is a healthy range for glucose?

Normal fasting glucose range is between 70 and 100 milligrams per deciliter (mg/dL), though it can vary by lab.

Do I need to fast for a glucose test?

Yes, for at least 8 hours before a fasting blood glucose test. Random glucose and HbA1c tests do not require fasting. Always follow test-prep instructions from your provider.

How often should I get tested?

There is no formal cadence recommendation for glucose testing. The U.S. Preventive Services Task Force (USPSTF) recommends screening adults aged 35 to 70 who have overweight or obesity for prediabetes and type 2 diabetes at least every 3 years. Fasting plasma glucose, HbA1c, or an oral glucose tolerance test can all be used for this screening.

Can glucose be tested at home?

Yes. Blood glucose meters and continuous glucose monitors are available, but lab tests are still required for diagnosis and ongoing care.

What symptoms suggest high blood sugar?

Excessive thirst, frequent urination, fatigue, blurred vision, or slow-healing wounds suggest high blood sugar.

What symptoms suggest low blood sugar?

Shakiness, sweating, irritability, confusion, or — in severe cases — seizures suggest low blood sugar.

Is glucose testing covered by insurance?

Yes. Screening and monitoring for diabetes are typically covered by insurance when it’s medically necessary, such as for diabetes screening or monitoring.

What tests are related to this biomarker?

• HbA1c (Hemoglobin A1C)

• Oral glucose tolerance test (OGTT)

• Basic metabolic panel (BMP) 

• Comprehensive metabolic panel (CMP)

• Urine glucose test

The information provided here is for informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always talk to a qualified healthcare provider about your specific health concerns.

Related biomarkers

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Uric Acid

Uric acid is the natural waste product when your body breaks down certain foods and drinks. It usually dissolves in your blood and is removed by your kidneys when you urinate.

Learn more about Uric Acid

Hemoglobin A1c (HbA1c)

Hemoglobin A1c (HbA1c) shows your average blood sugar levels over the last 2-3 months. When the number is in a good range it indicates that your blood sugar has been steady.

Learn more about Hemoglobin A1c (HbA1c)

Insulin

Insulin is a hormone that helps your body use and store sugar, or glucose, for energy. A healthy insulin level means your body is doing a good job of moving sugar from your blood into your cells, which helps keep your blood sugar steady.

Learn more about Insulin

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Reviewed by Felix Gussone, MD

Published 12/04/2025