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Doctor's Assessment Included

Every result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.

Metabolic

Blood glucose levels: what do they tell you about your blood sugar?

Fasting glucose reflects metabolic efficiency, which directly impacts energy availability and performance. Athletes benefit from understanding their baseline glucose regulation.

Reference Ranges

Male
mmol/l
Low 3.5 Normal 5.5 High
Female
mmol/l
Low 3.5 Normal 5.5 High

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

What It Measures

This test measures your fasting blood glucose, expressed in mmol/L. Normal values are between 3.5 and 5.5 mmol/L. A value between 5.6 and 6.9 mmol/L is considered prediabetes — your blood sugar regulation is impaired but not yet in the diabetic range. A fasting glucose of 7.0 mmol/L or higher (measured on repeat) indicates diabetes mellitus.

The test requires fasting for at least eight hours, so the measurement reflects your basal glucose regulation. For a more complete picture, glucose is sometimes supplemented with HbA1c, which reflects your average blood sugar over the past two to three months.

Why It Matters

Type 2 diabetes affects more than one million people in the Netherlands, and an estimated 1.1 million more have prediabetes without knowing it. Untreated, diabetes significantly increases the risk of cardiovascular disease, kidney damage, eye problems, and nerve damage.

Prediabetes is a reversible stage. With lifestyle adjustments — weight loss, more exercise, less sugar and processed carbohydrates — more than half of people with prediabetes can prevent developing diabetes. This makes early detection through a fasting glucose test or HbA1c very valuable.

When to Test

A fasting glucose test is useful with risk factors for diabetes: overweight (BMI > 25), family history of diabetes, high blood pressure, previously identified prediabetes, or polycystic ovary syndrome (PCOS). Everyone over 45 is advised to have blood sugar checked at least every three years.

With symptoms such as excessive thirst, frequent urination, unexplained weight loss, or persistent fatigue, a glucose test is strongly recommended. You must fast for at least eight hours before this test (only water is allowed).

Symptoms

Low Levels

Low glucose (below 3.5 mmol/L, hypoglycaemia) causes trembling, sweating, palpitations, dizziness, hunger, irritability, and concentration problems. In severe hypoglycaemia (below 2.8 mmol/L), confusion, blurred vision, and in extreme cases loss of consciousness can occur. Hypoglycaemia occurs most frequently in diabetes patients using insulin or sulfonylureas.

High Levels

Chronically elevated glucose (above 7.0 mmol/L fasting) does not always cause immediate symptoms, allowing diabetes to go unnoticed for a long time. When symptoms occur, they typically include excessive thirst, frequent urination (including at night), fatigue, blurred vision, and slow wound healing. At very high levels (above 15–20 mmol/L), diabetic ketoacidosis or a hyperosmolar state can occur, which is a medical emergency.

Lifestyle Tips

With prediabetes or elevated risk, lifestyle is the most powerful intervention. Just 5–7% weight loss reduces diabetes risk by 58%. Limit refined sugars and processed carbohydrates, choose whole grain products, vegetables, and proteins. Regular exercise (at least 150 minutes per week) directly improves insulin sensitivity. Adequate sleep and stress reduction are also relevant, as sleep deprivation and stress disrupt blood sugar regulation.

Frequently Asked Questions

What is a normal fasting glucose level?
Normal values are between 3.5 and 5.5 mmol/L. A value of 5.6–6.9 mmol/L indicates prediabetes. A value of 7.0 mmol/L or higher (on repeat) is consistent with diabetes.
What is the difference between glucose and HbA1c?
Fasting glucose is a snapshot of your blood sugar. HbA1c reflects your average blood sugar over the past two to three months. Together they provide the most complete picture of your blood sugar regulation.
Do I need to fast before a glucose test?
Yes, for a fasting glucose test you must not eat or drink (except water) for at least eight hours. This is needed to measure your basal blood sugar regulation without the influence of a recent meal.
What is prediabetes?
Prediabetes is an intermediate stage where your blood sugar is elevated but not yet in the diabetic range. It is a warning signal that your risk of type 2 diabetes is increased. With lifestyle adjustments, prediabetes is often reversible.
Can stress affect my blood sugar?
Yes, both physical and emotional stress raise blood sugar because stress hormones (cortisol, adrenaline) release glucose from the liver. With chronic stress, this can contribute to structurally elevated glucose.
How often should I have my glucose checked?
Without risk factors, a check every three to five years is sufficient from age 45. With risk factors (overweight, family history, prediabetes), annual monitoring is recommended.