Biochemical testing looks at the levls of specific substances and enzymes that are produced by chemical reactions in the body. Metabolic disorders are often the result of a missing or non-functional enzyme. When an enzyme is missing, greatly reduced in quantity, or is not working properly, the body cannot perform its usual chemical reactions. As a result, several harmful changes in body biochemistry can occur. These include accumulation of substrate, accumulation of precursors, deficiency of products, redirection of substrate into alternate pathways. Biochemical testing looks at the levels of these disturbances and can be used to detect several different metabolic conditions.