Glucose in Serum or Plasma (Fasting)

This test helps your doctor check how well your body is working and look for signs of illness. It may be used to confirm a diagnosis, monitor an ongoing condition, or guide decisions about your treatment plan.

Your doctor may order this test if you have symptoms like excessive thirst, frequent urination, unexplained weight changes, or fatigue. It’s also used to monitor diabetes management, screen for prediabetes, or evaluate metabolic health.

A small sample is collected by a trained professional, usually at a clinic, laboratory, or hospital. The process is quick and routine, and your sample is then sent to a lab where it is carefully analyzed.

A small blood sample is taken from your arm, usually in a clinic or lab. You’ll need to fast (no food or drink except water) for 8–12 hours before the test.

Most people find the procedure simple and quick. You may feel a brief pinch or slight discomfort during the collection, but it usually passes within moments. Afterward, you can typically return to your normal daily activities right away.

The process is quick and painless. You may feel a slight pinch when the needle is inserted, but most people tolerate it well. A bandage will cover the site afterward.

Follow any specific instructions from your healthcare provider before the test. You may need to fast for a certain number of hours, drink plenty of water, or temporarily avoid certain medications. Tell your care team about any medicines or supplements you take.

Follow your doctor’s instructions carefully. Avoid caffeine, alcohol, or strenuous activity before the test. If you’re pregnant, have diabetes, or take certain medications, discuss this with your provider first.