A 27-year-old female patient who came for branchial cyst excision was found to have cyanosis and a saturation gap during preanesthetic check-up and hence she was referred to haematology for further workup. She had a Hb of 9 gm% with all other baseline tests as normal. Blood samples were sent for methaemoglobin estimation and related work up to the National Institute of Immunohematology (NIIH) Mumbai. She was diagnosed as a case of Methemoglobinemia with a methaemoglobin level of 68.7% with NADH cytochrome B5 reductase activity of 10.82 IU/g Hb. The drug of choice for treatment is Methylene blue and hence G6PD deficiency had to be ruled out prior to initiating therapy. She was found to have a concurrent existence of G6PD deficiency. The blood sample was further sent to NIIH for genetic confirmation. We avoided methylene blue and other precipitating factors that could trigger a haemolysis. She was further consulted by the Patient blood management team to optimize her erythropoiesis and avoid unnecessary transfusions. Anaesthetic consultation and planning were done to avoid drugs that could induce haemolysis. She was started on Vitamin C, Niacin, hematinic and advised to follow up after a month. She was symptomatically better. Cyanosis had reduced, and Hb improved to 12 gm%. She was taken up for surgery with all precautions. The surgery and the post-operative period were uneventful. She was discharged on postoperative day 4 with an advice to continue Vitamin C & Niacin and to follow-up in Haematology OPD after a month.