To evaluate whether a very low glycated haemoglobin A (HbA1c) (<48 mmol/mol, 6.5%) during childhood compared to higher HbA1c values further decreases the risk for microvascular complications. Data were included from the 5116 patients with type 1 diabetes transferred from the Swedish paediatric diabetes quality registry to the Swedish National Diabetes Register (NDR), until 2014. All HbA1c values ever registered in the paediatric registry were used to divide patients into six groups based on the mean HbA1c. Values were compared with HbA1c registered in 2013 and 2014 in NDR, together with data on retinopathy, micro- and macroalbuminuria, age at onset and duration of diabetes. The group with lowest mean-HbA1c during childhood had also the lowest mean as young adults during 2013 and 2014. The most common complication as young adults was retinopathy. The proportion with macroalbuminuria was 3% in the lowest HbA1c group during childhood and 3.9% in the highest group, and lower in the groups in between. Microalbuminuria had the same pattern. Retinopathy increased with each HbA1c group. Children with the lowest HbA1c values had the lowest HbA1c values as adults. HbA1c was associated with retinopathy but the relationship with albuminuria was not obvious. © 2020 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.