Health Services

Patient Information on Fasting Samples and Glucose Testing


You should not eat or drink anything other than water for eight (8) hours before the test. Common tests that may require a fasting sample are glucose, cholesterol and triglycerides. Check with your provider or contact the laboratory at 210-916-5758 if you are unsure if you need to fast.

Glucose Test

May be measured on a fasting basis, randomly (anytime), post prandial (after a meal) or as part of an oral glucose tolerance test.

Oral Glucose Tolerance Test

Is a series of glucose tests. A fasting sample is collected and then the patient drinks a standard amount of a glucose solution which is followed by one or more additional glucose tests performed at set intervals to measure the glucose levels over time. The test can take up to three (3) hours. YOU CAN NOT EAT DURING THE TEST.

Post Prandial Glucose Test

A fasting glucose sample is drawn and then an additional glucose test is drawn after a specified amount of time following a meal. Typically two (2) hours after eating.

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