Drug malabsorption is one of the potential troubles after bariatric surgery. Evidence for diminished levothyroxine (L-T4) absorption has been reported in patients after bariatric surgery. This study reports 17 cases of hypothyroid patients [who were well replaced with thyroxine tablets (for >1 year) to euthyroid thyrotropin (TSH) levels before surgery (13 Roux-en-Y gastric bypasses (RYGB); 4 biliary pancreatic diversions (BPD))]. From 3 to 8 months after surgery, these patients had elevated TSH levels. Patients were then switched from oral tablets to a liquid L-T4 formulation (with the same dosage, 30 min before breakfast). Two-three months after the switch, TSH was significantly reduced both in patients treated with RYGB, as in those treated with BPD, while FT4 and FT3 levels were not significantly changed (RYGB group, TSH mu IU/mL: 7.58 +/- 3.07 vs 3.808 +/- 1.83, P < 0.001; BPD group, TSH mu IU/mL: 8.82 +/- 2.76 vs 3.12 +/- 1.33, P < 0.01). These results first show that liquid L-T4 could prevent the problem of malabsorption in patients with BPD and confirm those of previous studies in patients submitted to RYGB, suggesting that the L-T4 oral liquid formulation could circumvent malabsorption after bariatric surgery.