ABSTRACTIntroductionThe outcomes of completion thyroidectomy are not well‐documented. The study aim is to compare the risks of total thyroidectomy (TT), thyroid lobectomy (TL), and completion thyroidectomy (CT) using a large multi‐institutional database.MethodsAll cases of thyroidectomy without lymphadenectomy were identified using the CESQIP national database (2013–2023). Completion thyroidectomy was defined as contralateral lobectomy following previous lobectomy. Outcomes were examined including hematoma requiring evacuation, vocal cord dysfunction on post‐op laryngoscopy, and clinical concern for hypoparathyroidism.ResultsAmong 33,154 cases, TT, TL, and CT were performed in 19,057 (57%), 13,135 (40%) and 962 (3%), respectively. 30‐day hematoma rates were overall low: 135 (0.8%) in TT, 57 (0.5%) in TL, and < 10 (0.7%) in CT (p < 0.01). 30‐day vocal cord dysfunction was documented in 233 (1.4%), 159 (1.3%), and < 10 (1.0%) for TT, TL, and CT, respectively (p = 0.65). Temporary hypoparathyroidism was more common after TT than CT (989 (6%) versus 20 (2%), p < 0.01). Among 16,311 (49%) patients with reported long‐term outcomes, there were no differences in the rates of vocal cord dysfunction by type of operation (p = 0.34). However, long‐term hypoparathyroidism was more likely after TT than CT (237 (2.5%) versus < 10 (0.7%), p < 0.01).ConclusionIn this multi‐institutional endocrine surgery database, the reported long‐term complication rates after completion thyroidectomy were the same as for first‐time thyroid lobectomy. However, clinical hypoparathyroidism was 2.5‐fold more likely for total thyroidectomy than for completion thyroidectomy at 30‐days and remained 3.7‐fold higher in the long term suggesting that completion thyroidectomy does not pose a higher risk of complications.