Analysis of the composition of these fatty acids in phospholipids of RBC membranes provides information about their longer-term (approximately 125 days, RBC lifespan) dietary intake and their biosynthetic conversion to eicosanoids and certain metabolic anomalies (e.g. delta 6-desaturase deficiency). Here, FADS2 is linked to hyperinsulinemic hypoglycemia, familial, 4.