Reading a Fasting Blood Sugar Result

A fasting blood sugar test is done after a long break from food. That usually means at least 8 hours without eating.

It measures glucose, the sugar in your blood. No recent meal is being digested. So the number shows how your body handles sugar on its own.

Doctors compare your fasting number with standard ranges. A range is a set of numbers that acts as a guide.

The normal range is 70 to 99 mg/dL (3.9 to 5.5 mmol/L). The prediabetes range is 100 to 125 mg/dL (5.6 to 6.9 mmol/L). The diabetes range is 126 mg/dL (7.0 mmol/L) or higher.

Your number can be checked against these three bands.

One reading alone rarely settles a diagnosis, meaning the final answer. So doctors often repeat the test. Poor sleep, stress and a late meal can all change a fasting number.

Think of one reading like one cloudy day. One cloudy day does not decide the season. Repeat readings show the wider pattern.

If you take medicine, ask your care team how it may affect a fasting test.

Key takeaways

• A fasting test is taken after at least 8 hours without food.
• Doctors compare the number with the standard normal, prediabetes and diabetes ranges.
• One reading rarely settles a diagnosis, so repeat testing is common.

Try it

Before your next fasting test, write down your last meal time and ask your care team how long to fast.