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Fasting Blood Sugar – A first-line Test for Diabetes

What is Fasting Blood Sugar Test?

Also known as FBS for short, this is a blood sugar test done after a person fasts for a period of 8-12hours. Typically done after a person wakes up in the morning before they take breakfast. 

The fasting blood sugar level is a more accurate, reliable and reproducible indicator of how well the body is controlling blood sugar levels. Immediately after eating everybody experiences a spike in blood sugar levels. However,  several hours later, the level falls to the baseline level due to primarily the action of insulin.

In a person with abnormal insulin function, the blood sugar remains elevated and can be detected long after the meal is taken.

Indications: What are the uses of fasting blood sugar levels.

1.Diagnosis of  diabetes mellitus and other blood sugar abnormalities

Fasting blood sugar is an accurate and actually one of the most dependable to diagnose diabetes mellitus. 2 or more reading above the reference value are diagnostic of diabetes.

2. Monitoring treatment of diabetes.

Measuring your blood sugar in the morning gives the best indication how well antidiabetic  medication, dietary and lifestyle measures are working. The diabetes care team uses these measurements to make decisions for example, drug dose adjustment or dietary advice. Often, other tests like 2.hour post meal glucose levels and HbA1C are considered as well.

3. Assessment of Gestational Diabetes Mellitus (GDM)

We have a comprehensive article on laboratory management of diabetes here in case you are interested. 

FBS: How to test your morning sugar level at home

Testing blood sugar is quite simple. With modern glucometers, you will have results after a few steps. Take your blood sugar measurement immediately after waking up and before taking  a meal (water is acceptable)



  • Sanitize finger with alcohol soaked swab and air dry
  • Insert test strip into glucometer and wait for flashing blood drop icon
  • Prick finger with lancing device
  • Touch tip of test strip downwards on the drop of blood on the finger.
  • Read the results displayed on the glucometer screen
Fasting Blood Sugar Test
Fasting Blood Sugar Test with a glucometer

Be sure to record in your log carefully.

Interpreting Fasting Blood Sugar

According to the WHO The reference range for fasting blood sugar is 3.9-5.8mmol. Between 5.8- 6.9 is considered pre-diabetes or impaired glucose tolerance. FBS more than 6.8 usually indicate diabetes.

Its important to note for a known diabetic under management, the target FBS is is agreed upon by the diabetic care team based on your particular circumstances. Nowadays, the focus has shifted from obsessing on one figure to a more holistic and feasible and sustainable disease management. 

 …To Wrap Up

Fasting blood sugar is an simple but extremely important test in diabetes diagnosis and management. Understanding the FBS and its role in diabetes management is crucial to its proper utilization.

Cost of measuring blood sugar in Kenya

The cost ranges form KES 50 in pharmacies to as much as KES 400 in major hospitals .Luckily, for persons living with diabetes, glucometers have become affordable and over time the cost of doing blood sugar at hone averages KES 20.

You can find our glucometers here 

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Till next time, happy and healthy living!

Team labtestzote.

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