Glucose, Serum or Plasma (Mass Concentration)

Why Is This Test Done?

Your healthcare provider may order this test to check for high or low blood sugar, diagnose diabetes, evaluate how your body processes glucose, or monitor treatment for conditions like hypoglycemia or hyperglycemia. It’s also used in routine check-ups or during pregnancy to assess metabolic health.

What to Expect Before the Test

No special preparation is needed for this test. If blood is drawn from a vein (venipuncture), you may feel a slight pinch or discomfort, but it usually lasts only a few seconds. If a fingerstick is used, you might experience a small sting. Avoid eating or drinking for 8–12 hours before a fasting glucose test if instructed.

What Happens During the Test?

A healthcare professional will clean the area with an antiseptic, insert a small needle into your vein or prick your finger to collect a blood sample. The blood is then sent to a lab for analysis. Plasma or serum (liquid part of blood) is used to measure glucose concentration.

What Does the Test Result Mean?

Results are typically reported in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L). While reference ranges vary by lab, very high or very low values may signal diabetes, prediabetes, or other metabolic issues. Your provider will interpret results in the context of your health history and symptoms.