The following case is an account of interference of clear nail polish with pulse oximetry readings almost affecting critical surgical decisions previously not described in literature. A 19 years old female patient was diagnosed with papillary thyroid carcinoma and scheduled for total thyroidectomy and left cervical lymph node dissection surgery under general anesthesia. During the surgery, the patient lost 400 mL of blood and a critical blood transfusion decision was needed to be made. Based on the pulse oximetry readings, the patient SpHb was ranged between 7.1-7.3 g/dL. However, using invasive conventional blood testing methods the patient SpHb was ranged between 9.5-9.8 g/dL. Upon careful investigation, we noticed our patient had clear ultra-reflective nail polish on. We suspect that this was the reason and it is interfering with the pulse oximetry readings. Based on this discovery, a decision was made to not transfuse blood for the patient. The rest of the surgery was unproblematic and 20 minutes after surgery our patient woke up with no other problems. The above case should act as an important warning for future surgical staff and especially surgical preparation team. Clear nail polish is similar to having no nail polish except the ultra-reflective surface; therefore it is easily missed during surgical preparations. We suggest that all nails should be cleaned prior to surgery despite the presence of nail polish and we feel all surgical staffs should be warned on the possible danger of using pulse oximetry readings on a patient with clear nail polish. © 2016, E-Century Publishing Corporation. All rights reserved.