MLT GlobeGlucose, fasting (FPG)
Diabetes · also called FBS, Fasting blood sugar, FPG
What it measures
Fasting plasma glucose measures blood sugar after an overnight fast. It is used to screen for and diagnose diabetes and prediabetes and to monitor treatment.
Specimen and preparation
- Specimen: Sodium fluoride/potassium oxalate plasma
- Tube: Gray top
- Preparation: No food or caloric drink for at least 8 hours; water allowed. Unspun serum tubes lose about 5–7% glucose per hour.
Reference range
| Group | Range |
|---|---|
| Normal | 70–99 (3.9–5.5) mg/dL (mmol/L) |
| Prediabetes (IFG) | 100–125 (5.6–6.9) mg/dL (mmol/L) |
| Diabetes | ≥126 (≥7.0) mg/dL (mmol/L) |
Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.
Causes of high values
- Diabetes mellitus
- Stress hyperglycaemia (infection, surgery)
- Corticosteroids and thiazides
- Cushing syndrome and acromegaly
- Pancreatitis
Causes of low values
- Insulin or sulfonylurea excess
- Insulinoma
- Adrenal insufficiency
- Liver failure
- Delayed separation of sample (artefact)
Method
Enzymatic (hexokinase or glucose oxidase)
Good to know
Diabetes needs confirmation by a repeat test unless symptoms are clear. Critical values are usually <50 or >450 mg/dL (limits vary by lab).
Related tests
📱 Practise with a timer, track your score and earn certificates in the free MLT Globe app – Google Play or practise online.