Fasting Blood Sugar (FPG) Test

What Is Fasting Blood Sugar Test

Fasting blood sugar (glucose) test, also known as FPG test, is a blood test that measures the amount of sugar present in blood after 8 hours of fast. Fasting means that one should not take any food or drink (except water) for at least 8 hour before going for the test.

It is a routine blood test. Fasting blood glucose measurement is usually done in the morning so that one does not need to do fasting for throughout the day.

Fasting Blood Sugar Test Purpose

Fasting blood sugar (glucose) test is done

  1. To screen for blood sugar range abnormalities
  2. To diagnose diabetes, prediabetes, or gestational diabetes
  3. To monitor already diagnosed diabetes
  4. To determine the overall treatment strategy for the patient
  5. To know the overall health condition of the patient
  6. To know whether the diabetes treatment is working for the patient or not
  7. To know the outcome of diabetes treatment
  8. To determine if any change of ongoing diabetes medicine is needed or not
  9. To determine the risk of patients to get the diabetes

Fasting Blood Sugar Test Importance

The importance of fasting blood sugar test are the following

  1. To determine what precautions one can take to avoid getting diabetes, especially for those who have prediabetes.
  2. To know whether the diabetes is effectively controlled by the patient or not.
  3. To determine the strategy of diabetes treatment
  4. To make people aware about the bad effects of diabetes on our body, especially who have a family history of diabetes.
  5. To determine if any change of dose of diabetes medicine is needed or not based on the fasting blood sugar result.
  6. If there is any infection, to determine the body’s ability to control the infection.
  7. To determine how much immunocompromised a person is, based on the fasting blood sugar level in the blood.
  8. To know if the patient has hypoglycemia or low blood sugar level. This is of special importance because severe hypoglycemia is a life threatening condition. So who has a tendency of low blood sugar level, they should carry sugar (preferably glucose) with them all the time. So, if blood sugar falls than normal range, they should consume the glucose immediately.

Who Should Get Fasting Blood Sugar Test

One should do the fasting blood sugar test if have symptoms of diabetes, hypoglycemia, prediabetes, gestational diabetes. Also one should go for the test if there is higher risk to get the diabetes. This conditions include

  1. Age 45 years or older
  2. Family history of diabetes
  3. Overweight or obese
  4. Prediabetes
  5. Have any medical condition such as heart disease, high cholesterol, high blood pressure, polycystic ovarian syndrome, etc.
  6. Sedentary lifestyle such as lack of physical activity

It is important to note that during pregnancy hormonal changes occur. Due to this hormonal change, one can develop gestational diabetes. So, one should check blood sugar level during pregnancy.

Doctor can also advise you to do the fasting blood sugar test if you have the following symptoms

  1. More frequent urination
  2. Excessive thirst
  3. Excessive hunger
  4. Fatigue
  5. Increased number of infections
  6. Infections don’t heal quickly
  7. Tingling sensation in the hands and feet
  8. Constipation
  9. Eye problems, etc.

Fasting Blood Sugar Test Procedure

Fasting blood sugar test is a routine blood test that needs to be done after 8 hours of fasting. This is very important to note that one should not eat or drink except water for at least 8 hours before the test. One should also note that a very good sleep in the previous night is important.

Just like HbA1C test, PP sugar test, Lipid profile blood test, C-Reactive Protein Test, ESR Test, etc. fasting blood sugar test is done by drawing blood from one vein (preferably vein of arm) of our body. Next, the test result is prepared based on this blood sample.

You should always mention to your healthcare provider if you are taking any medicines, supplements, herbal products, etc. before going for the test. Several medicines can affect your blood sugar level in blood, so consult with your doctor before going for the test. Also, do not discontinue the medicines you are already taking without consulting with your doctor. Follow the doctor’s advise.

Drugs Affecting Blood Sugar Level

Drugs that affect the blood glucose levels are

  1. Corticosteroids
  2. Birth control pills
  3. Hormone therapy
  4. Diuretics
  5. Antipsychotics
  6. Aspirin
  7. Epinephrin
  8. Lithium
  9. Tricyclic antidepressants
  10. Monoamine Oxidase Inhibitors (MAOIs)
  11. Sulfonylurea
  12. Phenytoin

Temporarily Blood Sugar Increasing Factors

Factors that can temporarily increase the blood sugar level are

  1. Stress
  2. Surgery
  3. Trauma
  4. Heart attack
  5. Stroke

Fasting Blood Glucose Test Results

Normal Range

Normal Range of fasting plasma glucose is 70 to 100 mg/dL

If the fasting plasma glucose level is in between 100 mg/dL to 125 mg/dL, it means you have prediabetes.

If the fasting plasma glucose level is 126 mg/dL or higher, it means you have diabetes.

High Blood Sugar (Glucose) Level Causes

There are several reasons for high sugar in the blood. High blood sugar is usually seen due to the following causes

  1. Pancreatitis
  2. Hyperthyroidism
  3. Drugs
  4. Stress
  5. Trauma
  6. Surgery
  7. Prediabetes
  8. Pancreatic cancer
  9. Hormonal disorder, such as Cushing Syndrome, Acromegaly,etc.

Low Blood Sugar (Glucose) Level Causes

There are several reasons for low sugar level in the blood. The common causes of low blood sugar level are the following

  1. Overuse of insulin
  2. Liver disease
  3. Starvation
  4. Hypothyroidism (underactive thyroid gland)
  5. Underactive pituitary gland
  6. Abuse of alcohol
  7. Addison’s disease
  8. Kidney disease
  9. Insulinoma (pancreatic tumor)


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