Test Detail
Overview
Interpreting Results
FAQ's

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Written by
Dr. Betina Chandolia
BDS, MDS - Oral Pathology and Microbiology
Reviewed by
Dr. Lalit Mohan Gupta
MBBS, MD - Microbiology
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Glucose - Fasting Blood

(FBG)
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Glucose - Fasting Blood
You need to provide
Blood
This test is for
Male, Female
Test Preparation
  1. Do not eat or drink anything other than water for 8-12 hours before the test.

Overview


What is FBG?

The Fasting Blood Glucose Test is done to measure the levels of glucose in the blood after a period of fasting. This test is done to screen and diagnose prediabetes and diabetes.


Why is FBG done?

The Fasting Blood Glucose Test is done to:

·         Detect diabetes mellitus

·         Screen for high blood sugar in presence of risk factors of Diabetes

·         Detect diabetes during pregnancy or gestational diabetes

·         Monitor treatment efficacy in patients undergoing treatment for diabetes



What does FBG Measure?

Glucose - Fasting Blood Test is done to measure the levels of glucose in blood during period of fasting.

Glucose is the main source of energy for body. Carbohydrates consumed in the diet are broken down in the body to glucose, which is absorbed by the intestines and transported by the blood to various organs. The cells of these organs utilize the glucose to produce energy when required, and the excess is stored either as glycogen in the liver for short-term storage or in fat tissues as triglycerides for long-term storage. The uptake, utilization, and storage of glucose after it is absorbed in the intestines is facilitated by the hormone- insulin which is secreted by the pancreas. Insulin influences the transport of glucose to the organs like heart, brain, working muscles, etc. It also directs storage of excess glucose. The action of insulin reduces sugar levels in the blood.

After a meal, sugar levels increase in blood and insulin is secreted in response to reduce sugar levels until it becomes normal. If glucose levels fall too low in blood, another pancreatic hormone called glucagon is released, which directs the liver to convert stored glycogen into glucose and releases it into the blood. The insulin and glucagon hormones create a feedback mechanism to keep blood glucose levels within the normal range. Imbalance in their activity causes an excess or shortage of blood sugar.

Glucose - Fasting blood Test helps to determine if the body is able to utilize or store glucose efficiently. High levels of sugar in blood indicates diabetes or resistance to insulin. Type 1 Diabetes is caused when insulin is not produced or produced in very little quantity. Type 2 Diabetes is caused when insulin produced is not utilized effectively by the body. In both these cases, blood sugar level rises, while cells are deprived of nutrition.

Interpreting FBG results


Interpretations

Normal fasting glucose range: 70 to 99 mg/dL (3.9 to 5.5mmol/L)

Prediabetes: 99 to 126 mg/dL (5.5mmol/L to 7.0mmol/L)

Diabetes: Higher than 126 mg/dL (7.0mmol/L) in multiple subsequent tests


Answers to Patient Concerns & Frequently Asked Questions (FAQs) about FBG


Frequently Asked Questions about Glucose - Fasting Blood

Q. How is this test performed?
This test is performed on a blood sample. A syringe with a fine needle is used to withdraw blood from a blood vessel in your arm. The healthcare provider will tie an elastic band around your arm to make the blood vessels swell with blood. This makes it easier to withdraw blood. You may be asked to tightly clench your fist. Once the veins are clearly visible, the area is cleaned with an antiseptic solution and then the needle is inserted into the blood vessel to collect the sample. You will feel a tiny pinprick during the procedure. Blood sample once collected will then be sent to the laboratory.
Q. Is there any risk associated with this test?
There is no risk associated with the test. However, since this test involves a needle prick to withdraw the blood sample, in very rare cases, a patient may experience increased bleeding, hematoma formation (blood collection under the skin), bruising or infection at the site of needle prick.
Q. What is Hyperglycemia?
Hyperglycemia refers to a condition where the blood glucose level is above the normal range. This condition may indicate prediabetes or diabetes and may cause significant health problems.
Q. What are the symptoms of Hyperglycemia?
Symptoms of Hyperglycemia include: Increased thirst, frequent urge to urinate, weakness, tiredness (fatigue), blurring of vision and slow wound healing.
Q. What is Hypoglycemia?
Hypoglycemia is the condition where the blood sugar levels fall below normal. This is commonly found in case of nutritional deficiency.
Q. What are the symptoms of Hypoglycemia?
Symptoms of Hypoglycemia include: Excessive sweating, frequent hunger, shivering or trembling, confusion and blurring of vision
Q. What are the risk factors for Diabetes?
The risk factors for diabetes are: Being obese or overweight with low physical activity, having a blood relative diagnosed with Diabetes, having been diagnosed with hypertension, having low High Density Lipoproteins or high triglyceride levels, being diagnosed with Polycystic Ovarian Syndrome, having been diagnosed with gestational diabetes and cardiovascular diseases.
Q. Is there any preparation required before the test?
Inform the doctor about the medications you may be taking. No other specific preparations are usually required before this test.
Q. Can factors other than hormones and diet affect my blood sugar levels?
Yes, blood sugar levels can be increased by certain medications, during pregnancy, and even temporarily due to stress.
Q. What are the common complications of diabetes?
Diabetes causes an increase in blood sugar levels. Increased sugar levels, if not controlled, can cause severe damage to the muscles and nerves. This may give rise to a number of complications over a period of time. Some common complications of uncontrolled diabetes include: Heart diseases like coronary artery disease, heart attack; Diabetic Retinopathy (damage to the retina) which may cause blindness; Diabetic Neuropathy (damage to the nerves) at various parts of the body; Diabetic Nephropathy (damage to the kidneys) resulting in chronic loss of kidney function; Diabetic foot which can cause foot ulcers that may turn gangrenous. Apart from these, uncontrolled diabetes may also lead to other severe conditions like hearing impairment, a number of skin conditions, and may even lead to death.
Q. What other tests can be prescribed by your doctor in case the result of Fasting Blood Glucose test is not normal?
Additional tests that may be prescribed to diagnose diabetes in case of abnormal fasting blood glucose test result are: Urine Glucose Test, Blood Glucose - Post prandial (PP), Random Blood Glucose Test, Glycosylated Hemoglobin Test or HbA1c Test and Oral Glucose Tolerance Test.
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