A new study published in the journal ofCureusfound a hidden cardiovascular risk in patients with type 2 diabetes mellitus (DM). This research have confirmed that coronary microvascular dysfunction (CMD) which substantially raises the risk of major adverse cardiovascular events (MACE), even when large coronary arteries appear free of significant blockages. CMD refers to impaired function of the small coronary vessels that regulate blood flow to the heart muscle. Unlike the more familiar obstructive coronary artery disease (CAD), CMD does not involve major blockages and is highly difficult to detect. This underdiagnosis may leaves many diabetic patients vulnerable to heart attacks, heart failure, and early death. Between August 2022 and July 2024, this study enrolled 264 adults with type 2 diabetes of at least 5 years’ duration, all of whom showed less than 50% coronary stenosis on angiography or CT scans. Using transthoracic Doppler echocardiography, coronary flow reserve (CFR) was measured in the left anterior descending artery. A CFR value below 2.0 indicated CMD. The patients were then followed for 24 months. Of the 264 patients (mean age 58 years; 56.8% male), CMD was detected in 142 individuals (53.8%) which highlights its high prevalence in diabetics without obstructive CAD. During follow-up, completed in 243 patients, outcomes revealed a striking difference between groups. CMD patients suffered MACE events at nearly 3-times the rate of non-CMD patients (29.7% vs. 10.4%). CMD more than doubled the risk of myocardial infarction (Hazard Ratio [HR] 2.28). The risk of hospitalization for heart failure was nearly tripled (HR 2.85). Higher cardiovascular mortality was observed in the CMD group (7.8% vs. 2.6%). When adjusting for age, sex, hypertension, dyslipidemia, body mass index, and diabetes duration, CMD remained an independent and powerful predictor of poor outcomes (HR 2.41 for MACE, 95% CI 1.39–4.16, p=0.002). Kaplan-Meier survival curves confirmed that CMD patients had significantly shorter event-free survival. Overall, the findings signal an urgent need to incorporate CMD screening into diabetic care. Conventional tests focus on large-vessel blockages, missing microvascular dysfunction that quietly drives heart damage. Detecting CMD through CFR measurement could help physicians identify high-risk patients early and intervene with aggressive preventive strategies. Abrar, U., Khan, M. N., Farooq, S., Wakil, H., Azhar Ghauri, H., Khanam Sherwani, M. Q., Akbar, I., Ali, H., Akhtar, R., & Raza, A. (2025). Coronary microvascular dysfunction and risk of cardiovascular events in type 2 diabetes without obstructive coronary artery disease (CAD): A prospective study. Cureus.https://doi.org/10.7759/cureus.91092