The optimal surgical approach for differentiated thyroid cancer remains controversial, with debate regarding the comparative risks of upfront total thyroidectomy versus staged completion thyroidectomy following the initial lobectomy. This study aimed to assess the complication rates associated with these two strategies and identify the optimal timing for completion thyroidectomy using a multi-dimensional analysis of four cohorts: an institutional series (n = 148), the National Surgical Quality Improvement Program (NSQIP) database (n = 39,992), the TriNetX repository (n > 30,000), and a pooled literature review (10 studies, n = 6015). Institutional data revealed higher overall complication rates with total thyroidectomy (18.3%) compared to completion thyroidectomy (6.8%), primarily due to increased temporary hypocalcemia (10% vs. 0%, p = 0.004). The NSQIP analysis demonstrated that total thyroidectomy was associated with a 72% increased risk of transient hypocalcemia (p < 0.001) and a 25% increased risk of permanent hypocalcemia (p < 0.001). TriNetX data confirmed these findings and identified obesity and concurrent neck dissection as risk factors for complications. A meta-analysis showed that total thyroidectomy increased the rates of transient (RR = 1.63) and permanent (RR = 1.23) hypocalcemia (p < 0.001). Institutional and TriNetX data suggested that performing completion thyroidectomy between 1 and 6 months after the initial lobectomy minimized permanent complication rates compared to delays beyond 6 months. In conclusion, for differentiated thyroid cancer, total thyroidectomy is associated with higher risks of transient and permanent hypocalcemia compared to staged completion thyroidectomy. However, performing completion thyroidectomy within 1–6 months of the initial lobectomy may mitigate the risk of permanent complications. These findings can inform personalized surgical decision-making for patients with differentiated thyroid cancer.