Fasting Plasma Glucose Level (High Likelihood)

Why This Test Is Done

Your healthcare provider may order this test if you have symptoms like excessive thirst, frequent urination, unexplained weight loss, or fatigue. It’s also used during routine check-ups, especially for those at higher risk of diabetes, such as older adults, people with obesity, or those with a family history of diabetes.

What to Expect Before the Test

You’ll need to fast (not eat or drink anything except water) for at least 8 hours before the test. Your blood will be drawn from a vein, usually in your arm, by a phlebotomist. The process is quick and typically painless.

What the Results Mean

High results may signal diabetes or insulin resistance. Low results could indicate hypoglycemia (low blood sugar), though this is less common in fasting tests. Your provider will discuss results in the context of your overall health.

Common Causes of Abnormal Results

High fasting glucose can be caused by diabetes, stress, certain medications (like steroids), or infections. Low results may stem from overuse of insulin or oral diabetes medications, liver or kidney disease, or severe dehydration.