AIMS: Early in the COVID-19 pandemic, evidence emerged suggesting that people with diabetic retinopathy (DR) or other microvascular diseases had greater risk of severe short-term outcomes. This study evaluated longer-term outcomes, providing more generalisable evidence. METHODS: We identified a cohort of UKBiobank participants with diabetes and retrieved their diagnostic codes for a variety of microvascular diseases, complications of diabetes and systemic comorbidities. We investigated relationships between diagnoses and the study outcome: admission to Critical Care or death from COVID-19, taking age, sex and diabetes duration into account. We tested relationships, adding baseline covariates and weighting diagnostic codes according to their recency prior to COVID-19 diagnosis. RESULTS: In univariate analyses, DR (OR: 1·519, p = 0·016) and microvascular disease (OR: 2·002, p = 0·000) were associated with greater risk of the outcome. In multivariate analyses, as expected, respiratory disease was most strongly associated with the study outcome, microvascular disease second. Adjusting analyses by number of admissions (general health proxy) and weighted diagnostic coding (comorbidity severity at COVID-19 diagnosis indicator), did not improve predictive power of the model. CONCLUSIONS: The presence of microvascular disease in routinely-collected healthcare data predicts risk of COVID-19 severe outcomes, independently of general health, in a cohort of people with diabetes.