Glucose
What it measures, and what changes the number.
Glucose is the main sugar circulating in the blood and the body's primary fuel. This test measures its concentration in serum or plasma at the moment the sample is drawn, reported in mmol/L or mg/dL depending on the lab.
It is often ordered with Insulin, which together with fasting glucose is used to calculate HOMA-IR, and read alongside HbA1c or Fructosamine, which reflect glucose over longer periods rather than a single point in time. It commonly appears on panels with lipids such as Triglycerides.
Whether the sample was taken fasting or after eating makes a large difference, so reports often note the fasting state. Blood cells keep consuming glucose after collection, so a delay before the sample is separated, or a tube without a preservative such as fluoride, can lower the result. Labs may print it as Glucosa (suero/plasma).
Reference ranges labs publish
Each lab states an interval for its own method and the population it measured. They differ, they are not interchangeable, and none of them is a verdict on a single result.
- Everyone, 1 year and over, random (non-fasting) sample: 70 to 140 mg/dL (3.89 to 7.77 mmol/L) · Photometric (hexokinase) · Source: Mayo Clinic Laboratories, GLURA (Glucose, Random, Serum) (read 2026-09-24)
- Everyone, fasting sample: 70 to 99 mg/dL (3.89 to 5.5 mmol/L) · Enzymatic · Morning draw after an overnight fast · Source: Labcorp, 001032 (Glucose) (read 2026-09-24)
Usually reported in mmol/L or mg/dL.
Often read alongside: Insulin, HOMA-IR, HbA1c (NGSP), Fructosamine, Triglycerides
Calculators that use it: HOMA-IR calculator