The recommended sample diluent of the Human GDF-15 ELISA Kit EZ-Set (DIY Antibody Pairs) (EZ0767), Human FGF21 ELISA Kit EZ-Set (DIY Antibody Pairs) (EZ0994) and Human FGF19 ELISA Kit EZ-Set (DIY Antibody Pairs) (EZ1160) for serum is 1:1.