In people with a very specific clinical phenotype, it might be pragmatic to request Sanger sequencing (a method that sequences a single gene in a single reaction) [46] of the selected gene alone; for example, GCK testing in a patient with isolated fasting hyperglycaemia, or HNF1B testing in a patient with renal cysts and diabetes [4]. The gene discussed is GCK; the disease is Hyperglycemia.