Objectives To analyze data from the Scottish capillary thyroid stimulating hormone (TSH) screening program for hypothyroidism in Down syndrome to identify a threshold for capillary TSH elevation below which low venous free thyroxine (fT4) (10 mU/L) range is unlikely. Study design Review of proformas prospectively submitted on all children with Down syndrome referred via the screening program between 2003 and 2013. Results Ninety-nine patients with Down syndrome (50 females, 49 males) were identified, 76 school-age (≥5 years) and 23 preschool (10 mU/L. Fifty-three children had capillary TSH values of 4-5.9 mU/L of whom only one, a boy of 15.8 years, had subnormal venous fT4 (10 mU/L was found in 13 (4 preschool). Conclusions Venous fT4 is normal in almost all patients with Down syndrome with capillary TSH 4-6 mU/L. We propose an algorithm incorporating rescreening by finger prick after 6 months, rather than venepuncture, in schoolaged children with borderline capillary TSH elevation. Further data are needed before this approach can be recommended for preschool children.