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Epidemiological studies based on data from the UK Biobank and the English Longitudinal Study of Ageing (ELSA), suggest that diabetes is associated with increased risk of dementia, cognitive decline and neurodegenerative disorders. There are diverse hypotheses regarding the downstream pathways driving hyperglycaemia-induced neuropathophysiology, including disruption of the blood-brain barrier (BBB) and impaired function of the cells that form the BBB; endothelial cells (ECs), astrocytes and pericytes. However, the mechanism is still to be elucidated. Most in vitro systems utilised to study the BBB are planar and do not recapitulate the physiological complexity of the 3D architecture under flow conditions. Therefore, our aim was to determine the adverse effect of hyperglycaemia on BBB integrity using a complex, self- organising, 3D BBB model.ECs, astrocytes and pericytes were seeded into the microfluidic chip and perfusable vascular networks were allowed to form for 7 days when they were treated with either high glucose (30mM D-glucose), an osmotic control (30mM L-glucose) or normal glucose (5mM D- glucose) for 72 hours. Hyperglycaemia increased vascular permeability versus controls using Texas Red-labelled dextran (40 kDa) and live confocal imaging. Disorganisation of BBB vascular networks, (reduced tube area, branching & vessel length) was observed with alterations in cell morphology. Interestingly, areas of punctate staining were observed, indicative of cell death/apoptosis requiring further validation. Transcriptomic analysis using high quality total RNA from the chips revealed differential expression of 548 transcriptomes (165 genes upregulated and 382 genes downregulated) in high D-glucose treated BBB samples as compared to L-glucose treated samples.We have established a physiologically relevant model to understand the pathological effect of diabetes on the BBB. Identification of damaging and/or protective mechanism/s underlying diabetes-induced BBB disruption could lead to novel therapeutic strategies.