The requirement for fasting prior to sample collection stems from the reality that components of what is consumed become absorbed from the intestines and pass into the blood. Blood serves as the delivery system for the nutrients originating from dietary sources to target cells and tissues. Depending on the quantity of foods consumed, the content of the consumed food products, and time between consumption and sample collection, certain measurands are directly affected. Generally, reference intervals are based on a fasting state, with the purpose of minimizing the direct effect of what has been recently consumed on the analysis and subsequent clinical interpretation.
The required period of fasting may vary, but is generally in the range of 8 to 12 hours.
Listed below are common analytes for which fasting is often required: