Normal Blood Sugar Levels: Chart by Age and Meaning
Reviewed by the LabReadAI medical team
"Blood sugar" is the level of glucose, the body's main energy source. Normal blood sugar in adults is fairly stable, but it depends on whether you tested fasting or after eating, and on finger versus venous blood. Let's go through normal levels by age as a chart, the meaning of high and low levels, what counts as prediabetes and diabetes, and the meaning of your own result so a number is not just a number.
Normal Blood Sugar Fasting
In a healthy adult, fasting glucose (capillary, finger) is roughly 3.3–5.5 mmol/L; in venous plasma the upper limit is a little higher — up to 6.1 mmol/L. "Fasting" means 8–14 hours without food. A single small rise can follow stress or poor preparation — what matters is confirmation, not one point.
Normal Blood Sugar by Age: Chart
| Age | Normal fasting (mmol/L) |
|---|---|
| Children 1–5 years | 3.3–5.0 |
| Children/teens 6–14 years | 3.3–5.5 |
| Adults (finger) | 3.3–5.5 |
| Adults (venous plasma) | 4.1–6.1 |
| Older adults (60+) | slightly higher acceptable |
These are guides — exact references depend on the lab and blood type. Compare with the norm on your own form.
Blood Sugar After Eating and Prediabetes
Two hours after eating, a healthy person's sugar is usually below 7.8 mmol/L. Intermediate values are a "grey zone":
- Prediabetes: fasting 5.6–6.9 mmol/L or 7.8–11.0 at 2 hours — more in prediabetes.
- Diabetes: fasting ≥7.0 mmol/L (twice) or ≥11.1 at any time with symptoms — see type 2 diabetes.
To assess sugar over 2–3 months, glycated haemoglobin is used — the HbA1c panel.
Finger vs Venous Blood: The Difference
Venous blood (plasma) gives values about 10–12% higher than finger blood, so their norms differ. A glucometer (finger) is for self-monitoring, while diagnosis relies on venous plasma in the lab. A self-review of the marker is in glucose in blood: reading results.
When to See a Doctor
See a doctor for persistently high sugar, symptoms (thirst, frequent urination, weight loss, fatigue), and for very low sugar (sweating, trembling, confusion — dangerous). How to lower high sugar is in how to lower blood sugar.
To understand your own form in plain language, upload the test (PDF or photo) to the lab results interpretation service: the AI will explain glucose and other markers against reference ranges. This helps you understand the result but does not replace a doctor.
This article is informational. Diagnosis and treatment are the doctor's job.
For informational purposes only
This article is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. Please consult a healthcare professional for medical guidance.