Blood Glucose Test

What is a blood glucose test?

A blood glucose test, also known as a blood sugar test, measures the amount of glucose (sugar) in blood. This test is commonly used to diagnose and monitor diabetes, a condition characterized by high blood sugar levels.

What are the types of blood glucose test?

Capillary blood glucose test: This involves obtaining a small amount of blood, typically through a fingertip prick. The blood sample is applied to a test strip which is inserted into a glucometer. The glucometer quickly measures the blood sugar level and displays the results within seconds. It is often used for self-monitoring by individuals with diabetes, allowing them to check their blood sugar levels at home regularly.

Venous (plasma) blood glucose test: A phlebotomist (A trained medical professional who draws blood from an individual’s body) or a laboratory technician collects a blood sample from a vein through venipuncture, usually from the arm. The blood sample is sent to a laboratory for analysis, and results are available within a few days.

These glucose tests are generally included in a comprehensive blood panel where blood is drawn through veins and tested.  These include,

  • Fasting Blood Sugar (FBS): A fasting blood sugar test is conducted after a period of overnight fasting. A normal fasting blood sugar level is 99 mg/dL or lower. A reading between 100 and 125 mg/dL indicates the presence of prediabetes, while a measurement of 126 mg/dL or higher indicates the presence of diabetes.
  • Post Prandial Blood Sugar (PPBS): Postprandial means the period after a meal. The postprandial blood glucose test is performed two hours after having food to see the body’s response to a glucose post-meal. This particular test is conducted to observe how the body reacts to sugar and starch intake following a meal.
  • HbA1c: The HbA1c test evaluates the average blood sugar level over a period of approximately 2 to 3 months. A normal reading is below 5.7%. If the HbA1C falls between 5.7% and 6.4%, it indicates the presence of prediabetes. An HbA1C measurement of 6.5% or higher is indicative of diabetes.

Certain glucose blood tests involve consuming a sugary liquid and waiting for a designated period before obtaining a blood sample:

  • Glucose challenge test: This test is performed during pregnancy to screen for gestational diabetes. Screening means it detects an increased probability of gestational diabetes. Participants will be required to consume a sugary solution, followed by a one-hour waiting period before undergoing a blood glucose test. If it is higher than normal, an oral glucose tolerance test (OGTT) will be required for a definitive diagnosis.
  • Oral glucose tolerance test (OGTT): This test is used to diagnose gestational diabetes, as well as type 2 diabetes and prediabetes in non-pregnant individuals. Before consuming a sugary drink, a baseline blood sample will be taken. Subsequent blood samples will be collected at hourly intervals over the following 2 or 3 hours to monitor changes in blood glucose levels.

When would I need a blood glucose test?

If a patient experiences symptoms of high blood sugar (hyperglycemia) or low blood sugar (hypoglycemia), a doctor may request a blood glucose test.

Symptoms associated with high blood sugar include:

  • Excessive thirst (polydipsia)
  • Frequent urination (polyuria)
  • Intense hunger (polyphagia)
  • Unexplained weight loss
  • Blurred vision
  • Delayed healing of cuts or sores

Common signs and symptoms of low blood sugar are:

  • Trembling or shaking
  • Sweating and experiencing chills
  • Dizziness or feeling lightheaded
  • Increased heart rate
  • Intense hunger
  • Restlessness or irritability


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