Complications from diabetes mellitus such as retinopathy, nephropathy, and neuropathy are related to hyperglycaemia, diabetes duration, age, blood pressure, and albuminuria [1, 2]. Glycosylated haemoglobin (HbA1c) is a good biomarker for glycaemic control since it measures average blood glucose level over the recent 2–3 months [3]. Different organizations for diabetes care have varying HbA1c goals, but in Sweden the target for optimal glycaemic control is HbA1c levels ≤ 48 mmol/mol for children and adolescents without the presence of severe hypoglycaemia or frequent mild hypoglycaemia [1, 4]. Besides HbA1c, continuous glucose monitoring (CGM) with Time in Range (TIR), defined as blood glucose between 3.9 and 10.0 mmol/L, and Time in Target (TIT) defined as blood glucose between 3.9 and 7.8 mmol/l are very useful as markers for glycaemic control [5]. Since type 1 diabetes often develops during childhood, children and adolescents affected by the disease sometimes already developed complications when reaching adulthood. A recently published study showed that to avoid retinopathy that needed laser or intraocular injections and microalbuminuria 32 years after diagnosis with type 1 diabetes, an HbA1c below 53 mmol/mol and as normal as possible should be recommended [6]. However, it seems that other factors are related to the development of complications in type 1 diabetes. More markers able to identify the risk of complications early, perhaps even before they occur, are needed.

Fibroblast growth factor 21 (FGF21) is a peptide hormone that regulates energy homeostasis and is increased in ischemic heart disease, type 2 diabetes, insulin resistance, and dyslipidaemia where it has been shown to act as a compensatory reaction [7, 8]. Some studies have shown associations between FGF21 and nephropathy and retinopathy in type diabetes [7, 9] whereas another study of elderly patients with type 1 diabetes showed no such association [8].

Cystatin C is a non-glycosylated low-molecular-weight (13 kDa) protein that is found in nucleated cells without specificity for tissue and is independent of age and gender. Since it is filtered only by the glomerulus, it is considered a good marker for kidney function [10, 11]. It has potential as an early marker for diabetes related complications, since the association with a decrease in the glomerular filtration rate (GFR) and albumin to creatinine ratio (ACR) and progression to nephropathy in patients with diabetes have been shown [12, 13].

Lipocalin-2 is a novel adipokine which has been shown to relate to the level of inflammation in diseases and therefore linked to obesity and insulin resistance [14] Correlation between lipocalin-2 and vascular endothelial growth factor has been found in patients with proliferative diabetes retinopathy [15] and to retinopathy in patients with diabetes and overweight/obesity [16].

In zinc-dependent proteinase family Matrix metalloproteinase (MMP), MMP-9 is the largest molecule and is involved in many inflammatory events [17, 18]. Higher levels of MMP-9 have been shown in patients with diabetes and increased with diabetes duration [19]. Inhibition of MMP-9 could have a role in the treatment of retinopathy [20].

Even though there are studies of markers connected to complications from diabetes, as mentioned above, they are primarily conducted on adults or young adults and not on children. Children that develop type 1 diabetes have had the disease for a long time when reaching adulthood, and more studies are needed on this population.