What Blood Tests Need Fasting Preparation?

Blood tests are done to check for pregnancy, diabetes, cholesterol and vitamin and mineral problems. Most blood tests do not need any preparation. For those that do, make sure the instructions given by the physician are clear. If there are any questions, be sure to get the answers before testing day.

Glucose Tolerance

The glucose tolerance test, also known as the oral glucose tolerance test (OGTT), will check how the body metabolizes blood sugar. People with untreated type 2 diabetes will have high blood glucose levels. During pregnancy, high blood glucose levels can signal gestational diabetes. Fasting for this blood test is done to get an accurate reading of blood sugar levels. Ask the physician about any medications being taken and whether they will interfere with test results.

Cholesterol Levels

This blood test is also called a coronary risk profile. The blood is analyzed to check the levels of triglycerides, low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol, very low density lipoprotein (serum VLDL) cholesterol and total cholesterol values. Fasting before this test ensures the results are accurate.

Basic Metabolic Panel

The basic metabolic panel (BMP) blood test is usually ordered as part of a routine physical or to aid in diagnosing a specific medical problem. To get the most accurate results, fasting is a requirement. This test checks for glucose blood levels that could indicate diabetes or low blood sugar called hypoglycemia. Calcium is an important mineral in the body, and an imbalance could indicate problems in the kidneys, bones or pancreas.

It also measures the levels of blood urea nitrogen (BUN) and creatinine, which are waste products and filtered out of the blood by the kidneys. High levels could indicate the kidneys are not functioning properly.

Comprehensive Metabolic Panel

A comprehensive metabolic panel (CMP) is a blood test that can help diagnose liver disease, diabetes and kidney disease, as well as imbalances in protein and electrolyte levels. The difference between the basic and the comprehensive metabolic panels is two extra tests are done. One checks liver function by measuring albumin, a major protein in the blood produced by the liver, and total blood protein. The other measures alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and bilirubin. High levels of any of these could indicate the liver is not functioning correctly.


Follow instructions given by the physician or lab where the blood tests will be done 1. If there was a problem following the instructions, notify the technician who is to take the blood immediately.