Screening Test For DIABETIES: Blood Sugar Fasting Test

Oct 2022

What is blood sugar fasting test?

A fasting blood sugar fasting test is also called a fasting blood glucose test. It measures your sugar levels after fasting for at least 8 hours. Glucose is the main sugar found in your bloodstream and high levels after fasting may point to diabetes.

While fasting before the test, you can still drink water, but anything like coffee, tea, juice, and sodas should be avoided. A healthcare professional will draw blood for a vein in your arm, which will be sent to the lab for analysis.

After a meal, your blood glucose levels will normally increase over a few hours as you break down and absorb dietary carbohydrates. In healthy people, the pancreas will produce insulin to move glucose into tissues and out of the bloodstream. Thus, glucose levels will gradually drop after eating and stay low during fasting.

People with diabetes either don’t have enough insulin to reduce blood glucose (type 1 diabetes) or their body cannot effectively use insulin (type 2 diabetes). In a fasting blood glucose test, diabetics will have much higher blood sugar levels than non-diabetics, which can lead to many health problems in the long run.

Who Should Do the Test?

According to the American Diabetes Association, screening for diabetes is recommended in people over 45, or at any age if you have certain risk factors, including:

Being overweight
Having a close relative with diabetes
Belonging to a certain race/ethnic group
Having signs of insulin resistance
Gestational diabetes

Normal Range

Normal fasting blood glucose levels in healthy people are 70 – 125 mg/dL or 3.9 – 6.9 mmol/L.

Low blood sugar or hypoglycemia – below 70 mg/dL in diabetics or around 55 mg/dL (3 mmol/L) in healthy people.
High blood sugar or hyperglycemia – above 126 mg/dL or 7 mmol/L.

High Fasting Blood Sugar

For the purposes of this article, we will treat blood sugar in the range of prediabetes and above (>100 mg/dL or >5.6 mmol/L) as high.

Causes

Causes shown below are commonly associated with high glucose levels. Your doctor will interpret this test, taking into account your medical history and other tests results.

Chronic conditions that can increase fasting glucose levels include: