Blood glucose results are reported in different units (mmol/L in the UK, Australia and most of Europe; mg/dL in the US) and measured under different conditions — fasting, two hours after eating, or at a random point in the day. Knowing which measurement you're looking at is the first step to reading the number correctly.
This guide covers every common test type, what the reference ranges mean, and how to interpret results that sit outside them.
Fasting blood glucose
Fasting glucose is measured after at least eight hours without food or calorie-containing drinks. It's the standard first-line test for diabetes and pre-diabetes.
- **Normal:** below 5.6 mmol/L (100 mg/dL)
- **Pre-diabetes (impaired fasting glucose):** 5.6–6.9 mmol/L (100–125 mg/dL)
- **Diabetes:** 7.0 mmol/L (126 mg/dL) or above on two separate occasions
Post-meal (postprandial) glucose
A two-hour post-meal glucose is taken exactly two hours after the start of a meal. It reflects how effectively your body handles a glucose load.
- **Normal:** below 7.8 mmol/L (140 mg/dL)
- **Pre-diabetes:** 7.8–11.0 mmol/L (140–199 mg/dL)
- **Diabetes:** 11.1 mmol/L (200 mg/dL) or above
Random blood glucose
A random glucose test can be taken at any time, regardless of when you last ate. It's used when diabetes symptoms are present and a fast result is needed.
A random result of 11.1 mmol/L (200 mg/dL) or above, combined with classic symptoms such as excessive thirst, frequent urination and unexplained weight loss, is diagnostic of diabetes even without a fasting test.
HbA1c — the three-month average
HbA1c measures the percentage of haemoglobin coated in glucose over the previous two to three months. It avoids the day-to-day variability of single glucose readings and is the primary tool for diagnosing and monitoring diabetes.
- **Normal:** below 42 mmol/mol (6.0%)
- **Pre-diabetes:** 42–47 mmol/mol (6.0–6.4%)
- **Diabetes:** 48 mmol/mol (6.5%) or above
What affects a single reading
Glucose levels fluctuate significantly throughout the day. Stress, illness, physical activity, sleep deprivation and even the timing of meals all shift the number. A single elevated reading — particularly a random one — is rarely enough to draw firm conclusions. Context and trends over multiple tests matter far more.
If you're monitoring blood glucose at home, logging readings alongside the time, what you've eaten and any relevant activity gives a far richer picture than raw numbers alone. Looms lets you record and track your glucose readings over time, so patterns become visible across weeks rather than guesswork between appointments.
When to speak to your doctor
A fasting result above 5.6 mmol/L on a routine test is worth flagging — not necessarily alarming, but worth discussing. Two fasting results above 7.0 mmol/L on separate days meets the diagnostic criteria for diabetes and warrants prompt follow-up. Any result combined with symptoms like extreme thirst, blurred vision or unusual fatigue should be investigated the same day.