Blood glucose
Also known as: blood sugar, plasma glucose, serum glucose
The concentration of glucose, the body's main circulating fuel, in blood at the moment of sampling. Kept within narrow limits by insulin and glucagon, it rises after meals and in diabetes and falls dangerously in hypoglycaemia.
- Also known as
- blood sugar, plasma glucose, serum glucose
- Units
- mmol/L (UK) or mg/dL (US); 1 mmol/L = 18 mg/dL
- Measured by
- Blood glucose, HbA1c, Urinalysis
What it is and what it does
Glucose enters blood from the gut after meals and from the liver between them; insulin from the pancreas moves it into muscle and fat and switches off liver production, while glucagon, adrenaline and cortisol raise it. A fasting sample, a random sample and a sample two hours after a measured glucose drink each answer a different question, which is why the timing must be recorded with the result. Laboratories measure plasma glucose from a fluoride tube; fingerprick meters and continuous monitors estimate it from capillary blood or tissue fluid and read slightly differently.
Why it may be higher
- Diabetes and prediabetes
- Acute illness, infection, heart attack, surgery (stress hyperglycaemia)
- Corticosteroids and some other medicines
- Cushing syndrome, pancreatitis, pancreatic cancer
Why it may be lower
- Too much insulin or a sulfonylurea relative to food and activity
- Alcohol, especially without food
- Severe liver disease, adrenal insufficiency, sepsis
- Insulin-producing tumours (rare); reactive hypoglycaemia after gastric surgery
A high or low value can be associated with several different situations. The result is interpreted with other results, symptoms, history and clinical findings.
What can affect the result
- Time since the last meal or drink and what it contained
- Exercise, illness, stress and sleep
- A delay between sampling and analysis lowers the value unless a fluoride tube is used
- Meter readings differ from laboratory plasma values
Medicines that can change it
Each medicine page lists its effect on this marker under "Effects on tests and results", with the source.