Fasting Blood Sugar (FBS) Test

The blood sugar fasting test is done eight to ten hours after eating your last meal. It helps detect Prediabetes, Type 1 diabetes, Type 2 diabetes and Gestational diabetes. If your fasting blood sugar levels are above 125 mg/dL, it indicates that you may have diabetes mellitus and your doctor may advise a few more tests to confirm the diagnosis.

This test can be taken by anyone to screen themselves for diabetes and by people diagnosed with diabetes to monitor their blood sugar control.

The blood sugar fasting test is a blood glucose test that helps determine blood sugar levels in your body after fasting for more than 8 hours. In case a person has diabetes, these levels are high. The result of the blood sugar fasting test will indicate high levels of glucose in blood.

In healthy individuals, blood sugar levels drop when there is no glucose intake through food. In case of fasting or not having meals in a while, blood sugar levels decrease. If you have prediabetes, diabetes or gestational diabetes, your blood sugar fasting test results readings may be high.

Why is the blood sugar fasting test prescribed?

The blood sugar fasting test is prescribed for the purpose of:

1. Screening - Screening tests are meant to help in the early diagnosis and prevention of serious health issues. Anyone above 30 should get an annual screening for diabetes.
2. Diagnosis - Diagnose diabetes or prediabetes in adults. For a person prone to diabetes or with any symptoms of high or low blood glucose,  blood sugar fasting test results will be helpful in the diagnosis of the condition.
3. Monitoring - Those diagnosed with any type of diabetes need regular monitoring of fasting blood glucose levels to check for the effectiveness of ongoing treatment, dietary and lifestyle modifications.

Other names of fasting blood sugar test

• blood sugar fasting
• 10-hour fasting blood sugar
• Fasting Glucose
• Fasting Blood Glucose
• BS (F)
• FBS

What does the test measure?

The fasting blood sugar test measures your blood glucose levels after not having any meal for 8 to 10 hours. When a person eats something, the glucose from the food is released and absorbed into the bloodstream. The human body produces insulin to facilitate the uptake of glucose from the blood to the cells of your body for the production of energy. When a person has type 2 diabetes, gestational diabetes or prediabetes, the cells of the body do not respond well to insulin - a condition called insulin resistance and the pancreas overwork to produce more insulin than required. Another reason is the autoimmune damage to insulin-producing cells of the pancreas as in type 1 diabetes, where the blood glucose levels shoot up due to insufficient insulin.

This test helps to measure the glucose levels in the blood, usually after overnight fasting.

Who is the blood sugar fasting test prescribed for?

The blood sugar fasting test is advised equally for all genders and age groups. A blood sugar fasting test is used to diagnose the following health conditions:

• Prediabetes
• Type 1 diabetes
• Type 2 diabetes
• Gestational diabetes
• Other types of diabetes

People with a high risk of developing diabetes should get the fasting blood sugar test done. You are at risk for developing diabetes if:

• You are above 40 years.
• You have a family member suffering from diabetes.
• You are pregnant with type 1 or type 2 diabetes.
• You are pregnant with gestational diabetes.
• You are overweight or obese.
• You have been tested for high blood sugar levels after meals.
• You are physically less active.
• If you are a female with PCOS.
• If you are on long term steroid medications.
• If you have habits like smoking or excessive alcohol consumption.
• If you notice the following symptoms indicating diabetes like:

• Excessive hunger and thirst
• Increased frequency of urination
• Recurrent infections
• Weakness
• Unexplained weight loss
• Blurring of vision
• Delayed healing of wounds

The blood sugar fasting test is a test that is done by taking your blood sample. This blood sample for the blood sugar test procedure is drawn after 8 to 10 hours of fasting. This test can be accompanied by the Urine Sugar test, HBA1c for diabetes and in some cases, the Lipid Profile test.

Test preparation

The blood sugar fasting test requires you to give a blood sample to conduct the test.

Before the test

You need to fast for 8 to 10 hours the previous night and give your blood for testing your fasting blood sugar in the morning. During the period of fasting, the person can have water. No food is allowed. Regular medication, including diabetes medication, should be taken as prescribed.

During the test

There are no specific instructions during the blood sugar fasting test. It is a quick blood test that gets done in 5-10 minutes. The blood sample is taken from the veins of your arm. Dress accordingly.

After the test

A routine schedule can be followed after the blood sugar fasting test. In some cases, the blood sugar postprandial test might also be needed. Check with the doctor and accordingly carry on the rest of the activity throughout the day.

Test inclusions: What parameters are included in the blood sugar fasting test?

The blood sugar fasting test measures the blood sugar levels in your body 8 to 10 hours after the last meal.

Your fasting blood sugar test results are usually ready within 1-2 hours of doing the test. However, this duration may vary from lab to lab.

The normal values and reference ranges of the test may vary from lab to lab. Please refer to the ranges mentioned in the report and consult a doctor to understand the interpretation of lab reports.

There is a possibility of the blood sugar fasting levels going below 70 mg/dL due to medication. This would be a good indicator for the doctor to change the dosage or the medicine. Usually, 2 or more different blood glucose test results are considered for a diagnosis of diabetes.

How frequently should you take the blood sugar fasting test?

The blood sugar fasting test is repeated based on the following parameters:

• Whether a person has type 1 or type 2 diabetes.
• The overall blood sugar control irrespective of medicine.
• Certain medicines prescribed for diabetes require frequent testing of blood sugar fasting.

The frequency for each of these conditions is as follows:

• For the person who has type 2 diabetes, repeat the blood sugar fasting test once every week or as advised by your doctor.
• For people with type 1 diabetes, it is advisable to repeat the test every day. This daily test can be on a home blood sugar monitoring device.
• For those who have prediabetes, a blood sugar fasting test is prescribed every six months for monitoring purposes.
• For patients where diabetes is not well controlled, repeat the test every week in a lab along with daily monitoring on a home testing machine.
• Repeat the blood sugar fasting test when the diabetologist or endocrinologist changes the treatment plan. Repeat the test one month after starting the new medication.

Type 1 Diabetes Mellitus, Type 2 Diabetes Mellitus, Prediabetes, Other Types Of  Diabetes

The pricing for an FBS test fluctuates based on the location and the laboratory. Typically, the cost of an FBS test falls within the range of INR 89 to INR 329. Here's a breakdown of the average expenses for an FBS test in various major cities across India: