Glucose is the sugar in your blood and the body’s main source of energy. A fasting glucose level is used to gauge the risk of prediabetes and diabetes. Here’s what it all means, in plain language.
| Category | Reference range |
|---|---|
| Normal (fasting) | 3.9–5.5 mmol/L |
| Prediabetes (fasting) | 5.6–6.9 mmol/L |
| Diabetes possible (fasting) | 6.1–7.0 and above (venous plasma) mmol/L |
Cut-off values differ slightly between fingerstick and venous blood, and from one lab to another. Only a doctor can make a diagnosis, and only from several measurements. Check the reference range printed on your lab report.
When you eat, carbohydrates are broken down into glucose — the “fuel” your cells run on. The hormone insulin helps cells take that fuel in. A fasting glucose test shows how well your body handles sugar when you haven’t eaten for a while.
High fasting sugar can point to prediabetes or diabetes — a sign that cells are having a harder time taking glucose in. But a single high reading is not a diagnosis.
Low blood sugar (hypoglycemia) is most common in people being treated for diabetes, after a long stretch without food, after alcohol, or after heavy exertion. Symptoms include shakiness, sweating, hunger, weakness and irritability. A sharp drop in blood sugar needs a doctor’s attention.
Fasting glucose is measured in the morning, after 8–14 hours without food (water is fine). If you ate before the test, the result will come out higher than it should and cannot be read as a “fasting” value.
One result outside the range is a reason to repeat the test and talk it over with your doctor — not to diagnose yourself on the spot.
No need to decode the numbers yourself: take a photo of the report and the app explains “Glucose” and the rest in plain words — what is normal and what deserves attention.
Get the appOpen in TelegramRoughly 3.9–5.5 mmol/L for fingerstick blood taken while fasting. Values of 5.6–6.9 may point to prediabetes. The exact cut-offs depend on the type of blood sample and the lab, and the diagnosis is made by a doctor.
The usual advice is 8–14 hours without food. Water is fine. Coffee, tea with sugar and smoking beforehand can skew the result.
No. Diabetes is not diagnosed from a single test. It takes a repeat measurement and, as a rule, additional tests (HbA1c, a glucose tolerance test) that a doctor interprets.
This material is for general information only. It is not a medical opinion and does not replace a consultation with a doctor. Reference ranges depend on the laboratory and the method — rely on the range printed on your own report. Your doctor makes the final interpretation. This page is a translation of the Russian original. The medical review applies to the original text.
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