Sleeve gastrectomy (SG) is a popular surgery for morbid obesity because of minimal complications, while somewhere uncommon micronutrient deficiencies occur that make problems. One of these rare complications is dry beriberi (BB). A 20-year-old girl with obesity that a few months after SG had non-specific symptoms like nausea, vomiting, debilitating weakness, burning, and tingling in her feet, which led to more tests and imaging and confused the physicians. During the next two months, she had a 40 kg weight loss. The critical test that helped diagnosis was Electromyography and Nerve Conduction Velocity (EMG/NCV), which showed subacute axonal sensory-motor polyneuropathy and decreased level of vitamin B1, proved the patient's diagnosis was dray BB. SG may contribute to vitamin and trace elements deficiency development. One of the micronutrients that deficiencies can disturb the patient is vitamin B1 deficiency. Vitamin B1 deficiencies could be demonstrated with peripheral polyneuropathy, beriberi, or Wernicke-Korsakoff syndrome. Based on decreased vitamin B1 and EMG/NCV results, the diagnosis had been dry beriberi corrected with supplement therapy. Thiamine deficiency should be suspected in all patients with vomiting, neurological symptoms, and rapid weight loss post-bariatric surgery (BS), even after restrictive surgery. Especially when a patient reports substantial weight loss and vomiting in short order. Hopefully, this case report will make any patient hospitalized with similar conditions evaluated for beriberi and again multivitamin supplementation therapy after SG is emphasized. •Rapid weight loss after sleeve gastrectomy may cause thiamine deficiency.•Restrictive surgeries like sleeve gastrectomy may induce thiamine deficiency.•Multi vitamin supplementation therapy after sleeve gastrectomy is mandatory.