Lab test glossary · Blood sugar
Blood Glucose: what it means
Also known as: fasting glucose, blood sugar
Blood glucose is the amount of sugar in your blood at the moment of the draw; whether you were fasting changes how it's read.
What it measures
Glucose is your blood sugar at a single point in time. Unlike A1c, it's a snapshot — heavily influenced by when and what you last ate — so it's usually specified as fasting (typically 8+ hours without food) or random.
Typical range
A fasting glucose under about 100 mg/dL is generally considered normal, 100–125 mg/dL is the prediabetes range, and 126 mg/dL or higher on repeat testing supports diabetes — interpretation depends on fasting status and is your clinician's call.
Reference ranges differ between labs and are printed on your own report — always read your result against that range, not a general one.
What a high result can mean
- Recent food intake (for a non-fasting sample)
- Prediabetes or diabetes
- Stress, illness, or certain medications like steroids
A high value is a starting point for a conversation, not a diagnosis — many causes are benign or temporary.
What a low result can mean
- Longer-than-expected fasting
- Certain diabetes medications or insulin
- Less commonly, hormonal or liver conditions
Why the trend matters
A single glucose can swing with your last meal; the trend across fasting draws is what reveals a genuine shift in how your body handles sugar.
When to talk to your doctor
A fasting glucose of 100 mg/dL or above is worth reviewing with your doctor, ideally alongside an A1c for the fuller picture.
Frequently asked questions
What is a normal fasting glucose?
A fasting glucose under about 100 mg/dL is generally considered normal, 100–125 mg/dL is the prediabetes range, and 126 mg/dL or higher on repeat testing supports diabetes — interpretation depends on fasting status and is your clinician's call.
Why is my glucose high in the morning?
Morning glucose can be higher than expected due to normal overnight hormone rhythms, and a non-fasting result reflects your last meal. A single value is read alongside the trend and, ideally, an A1c.
This page is general education about a common lab test — it isn’t medical advice and can’t interpret your specific result. What a value means depends on your history, symptoms, and the rest of your labs, which is a conversation for you and your clinician.