LabCorp Test

Glucose Plasma Test

Quick Overview

Fasting blood sugar. Determines if your blood glucose level is within healthy ranges.

Test #001818


Availability: In stock

Also Known As Blood Sugar, Fasting Blood Sugar, FBS, FPG, Random Blood Glucose.
Preparation Fasting for 10-12 hours required.
Test Results 1-2 days. May take longer based on weather, holiday or lab delays.


The test requires individuals to fast for 10 – 12 hours before giving blood for the test.  The fasting should be done overnight and the blood test should be completed the next morning to obtain the most accurate results.  Individuals are allowed to drink water and to take medications during the fast.

Why It Is Used
The glucose plasma test is primarily used to test for and diagnose Type 1, Type 2, and gestational diabetes.  The test is also used to detect complications of diabetes and to track the results of diabetes treatment.

How It Works
Fasting for an extended period of time causes glucagon, a peptide hormone produced by the pancreas, to be released into the bloodstream.  The glucagon hormone is used to increase glucose in the blood by stimulating the liver to transform its stores of glycogen into glucose.  When glucose enters the bloodstream, it signals the body to pump insulin into the bloodstream to help transport the glucose from the blood into cells to be stored as energy.  Glucagon, along with insulin, is used by the body to maintain a healthy level of glucose in the blood.  In a person with diabetes, however, he or she may not be able to produce enough insulin to manage the glucose that was stimulated by the glucagon, causing glucose blood levels to remain high. 

Test results are interpreted by looking at the levels of glucose found in the blood.  Glucose is measured in milligrams per deciliter (mg/dL) and can fall into one of four categorizations that have different medical implications.  Normal results vary based on what test is being used.  The following results are representative numbers based on the glucose plasma fasting test. 

  • Below 70 mg/dL: blood glucose levels lower than 70 mg/dL after the fasting test indicate an abnormally low level of blood sugar and may be cause for a diagnosis hypoglycemia.
  • 70 mg/dL to 99 mg/dL: blood glucose levels that fall within this range after fasting for 10-12 hours are considered to be normal and healthy.
  • 100 mg/dL to126 mg/dL: after fasting blood glucose levels in this range indicate a possible diagnosis of pre-diabetes and a heightened risk of developing diabetes.
  • Above 126 mg/dL:  If a blood glucose level is above 126 on the glucose plasma test, then a diagnosis of diabetes will likely be made.

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