GNMT and hyperinsulinemic hypoglycemia, familial, 4: Furthermore it is unknown whether methionine levels are increased in newborns with GNMT deficiency although the normal blood spot methionine level (19.5 μmol/l, ref. values 15–47) obtained at newborn screening in one patient (Rakic et al 2015) may indicate that hypermethioninemia is not present from birth.