Metacognition, the ability to monitor and control one's cognitive processes, is crucial in high-stakes medical diagnoses. In two studies, we examined metacognitive processes in radiological and dermatological decision-making, focusing on how confidence and thinking time influence diagnostic accuracy and efficiency. Medical doctors (N = 150) assessed medical images, bone X-rays and skin images, providing diagnoses, confidence ratings, and recommended next steps (e.g., ordering additional tests, consulting experts). Key measures included diagnostic accuracy, monitoring accuracy (calibration and resolution), and strategic allocation of thinking time. As with mundane lab tasks, medical professionals exhibit well-calibrated confidence in easy cases but compromised success accompanied by pronounced overconfident in the time-consuming cases. Senior professionals not only performed better than juniors, but were more reliable in their confidence ratings, and made better next step decisions. Analyses of the misleading cases were done based on domain specific knowledge. These analyses exposed cases especially susceptible to time wastage and overconfidence across expertise levels. Recognizing when confidence is miscalibrated, is key to reducing errors and improving efficient decision-making. Further research should consider interventions to enhance metacognitive skills in medical practice.