Diabetes Tests Methods, Levels and Their Meanings

What is a Blood Glucose Test?

A blood glucose test is used to diagnose type 1 and type 2 diabetes, by measuring the amount of sugar (glucose) in your blood. It is also essential to monitor glucose levels in those already have the condition.

Types of Diabetes

Diabetes is a set of diseases that affect how your body handles blood sugar. If your blood sugar levels are high and continue to be high (hyperglycaemia), you are probably dealing with diabetes.

Main types of diabetes and related conditions include:

• Type 1 Diabetes Mellitus – In this condition, the immune system attacks the pancreas's insulin-producing cells. It generally appears in childhood and requires insulin injections for control.
• Type 2 Diabetes Mellitus – This condition typically appears in adults when the body either resists insulin or fails to produce enough. Management includes lifestyle changes, medications, and sometimes insulin.
• Gestational Diabetes Mellitus (GDM) – This condition occurs during pregnancy and typically goes away after giving birth. However, it raises the chance of getting type 2 diabetes in the future.
• Non-Diabetic Hyperglycaemia (NDH) – This indicates that blood sugar levels are above normal but not high enough for a diabetes diagnosis. It used to be called prediabetes and can lead to a higher risk of type 2 diabetes.

Blood Glucose Tests

Several tests can measure blood sugar levels:

Random Blood Glucose Test

A blood sample can be taken at any time to help find out if someone has diabetes. If the result is 11.1 mmol/L or more, it indicates diabetes. To confirm the diagnosis, a fasting blood test is often required.

Fasting Blood Glucose Test

A random blood glucose test does not confirm diabetes and a fasting blood glucose test is recommended. After at least eight hours of fasting, a blood sample is taken and analysed.

Results are interpreted as follows:

• Below 5.6 mmol/L – Normal blood sugar level
• 5.6 to 6.9 mmol/L – Indicates prediabetes (NDH)
• 7 mmol/L or higher – Suggests diabetes

If your blood sugar is 7.0 mmol/L or more and you have symptoms such as excessive thirst, frequent urination, or fatigue, a repeat test is not required for a diagnosis.

Oral Glucose Tolerance Test (OGTT)

This test is mainly used to diagnose gestational diabetes or borderline high blood sugar levels (NDH). It is less commonly used for diagnosing diabetes today.

For this test, a person must fast overnight for at least eight hours but no more than 16 hours. At first, a fasting plasma glucose sample is taken and then, the individual consumes a 75g glucose drink orally.

The standard OGTT involves measuring blood glucose levels five times over three hours. However, some doctors choose a simpler method, taking a baseline blood sample followed by another sample two hours after consuming the glucose solution. A result of 11.1 mmol/L or more confirms diabetes.

HbA1c Blood Test

This test measures average blood sugar levels over the past two to three months. It does not require fasting. If you have diabetes, your GP may take this test every 3-6 months.

• 20-42 mmol/mol (4-6%) – Normal range for non-diabetics
• 42-47 mmol/mol (6.0-6.5%) – Increased risk of diabetes (NDH)
• 48 mmol/mol (6.5%) or above – Diabetes diagnosis

For those with diabetes, treatment aims to keep HbA1c below 48 mmol/mol (6.5%), though individual targets may vary. If medication increases the risk of hypoglycaemia, the target is usually 53 mmol/mol (7%).

Home Blood Sugar Monitoring

People with diabetes, especially those on insulin, should regularly check their blood glucose levels. Blood glucose levels are usually checked before and after meals, as well as at bedtime to help individuals adjust their medication, diet, and physical activity as needed. Methods include:

• Blood Glucose Meter – A drop of blood from a finger prick is placed on a test strip and analysed with the device.
• Continuous Glucose Monitoring (CGM) – Worn devices track glucose levels throughout the day, reducing the need for finger pricks.

Urine Test for Glucose

Normally, urine does not contain glucose. However, if blood sugar levels rise too high, excess glucose passes into the urine.

A urine dipstick test can detect this, but a blood test is required to confirm diabetes, as some people naturally excrete glucose despite normal blood sugar levels.

Last Word

Feeling anxious about a blood sugar test is totally normal, but early diagnosis and treatment of diabetes are essential for long-term health. Think of it as a step towards protecting your future well-being.

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