Traditional risk factors underestimate fracture risk in individuals with diabetes. In this population-based case-control study we aimed to determine T-score thresholds for type 1 and 2 diabetes (T1D and T2D) with equivalent risk of fractures as that of individuals without diabetes and a T-score of -2.5.

We collected dual energy x-ray absorptiometry (DXA) data (2000–2019), information on diagnoses (1977–2019) and redeemed medications (1997–2019) from the National Danish Registries which are linked by a unique identifier. Cases were individuals with the first incident major osteoporotic fracture (MOF) within two years before or one year after a DXA and controls were fracture free and matched on age, gender, and time period of the DXA. Logistic regression modelling was used in the case-control analysis.

We identified 17,703 cases and 17,703 controls. T1D and T2D were associated with an increased risk of MOF (odds ratio: 1.8, 95 % CI:1.4;2.3 and 1.2, 95 % CI:1.1;1.3, respectively) adjusted for hip BMD. T1D and T2D patients had a similar risk of MOF at T-scores (total hip) = -1.4 and -2.1, respectively, as patients without diabetes with a T-score of -2.5. For hip fracture, the equivalent risk was correspondingly reached with T-scores of -1.9 and -1.6. Similar findings apply for femoral neck and lumbar spine BMD.

Compared to individuals without diabetes, fracture risk was increased in patients with T1D and T2D independent of BMD. Our study suggests that the T-score thresholds for treatment initiation in T1D and T2D should be increased.