Succinylacetone-13C7 is a labelled analogue of Succinylacetone. Succinylacetone (SA) is a specific marker for the inherited metabolic disease, hepatorenal tyrosinemia. It was developed a stable-isotope for the determination of SA in dried blood spots (DBS) and liquid urine using a 13C4-SA as internal standard. The method was applied retrospectively and prospectively for the diagnosis of hepatorenal tyrosinemia and for follow-up of patients under treatment.