Purpose
We carried out a meta-analytic synthesis to evaluate the association between diabetes mellitus (DM) and related clinical outcomes, co-morbidities, their risk factors and resource utilization in patients with COVID-19.

Methods
The MEDLINE and Web of Science databases were reviewed for identification of eligible studies. Meta-analysis was carried out using Review Manager 5.3. The random- effects model was used to compute the pooled estimates of odds ratio (OR)/mean difference and 95% confidence interval (CI).

Results
A total of 14 studies including 3,644 individuals without DM and 1,428 with DM were included in the meta-analysis. Cardiovascular diseases (CVDs) [OR 2.91, 95% CI 2.34, 3.63], hypertension [OR 2.19, 95% CI 1.39, 3.46], acute kidney injury (AKI) [OR 3.59, 95% CI 1.46, 8.84], cerebrovascular disease [OR 2.09, 95% CI 1.22, 3.61], and acute respiratory distress syndrome (ARDS) [OR 3.40, 95% CI 2.09, 5.55] were significantly associated with DM in COVID-19 patients compared with non-DM patients (p < 0.05 for all instances). Mortality was significantly higher among COVID-19 patients with DM [OR 2.46, 95% CI 1.68, 3.58]. Intensive Care Unit (ICU) admission and use of mechanical ventilation were significantly associated with COVID-19 patients with DM [OR 2.79, 95% CI 1.79, 4.34], and [OR 3.33, 95% CI 2.05, 5.42], respectively. No significant difference was observed in the length of stay (LOS) and hospitalization.

Conclusions
This meta-analysis shows that CVDs, hypertension, AKI, cerebrovascular disease, and ARDS are significantly higher among DM patients with COVID-19 compared with non-DM patients. Mortality, ICU admission and the use of mechanical ventilation were significantly associated with COVID-19 patients with DM. Further long-term, multinational and large sample size clinical studies are warranted to justify the current findings.