Abstract Disclosure: V.A. Mendpara: None. P.P. Rao: None. M.V. Kellis: None. M.D. Lundholm: None. Background: This case highlights the potential severe thrombotic consequences of blood thinner medication interruption for thyroid fine needle aspiration (FNA). Case Presentation: A 77-year-old woman came to the endocrinology clinic for follow-up on thyroid nodules. She was a former smoker with controlled type 2 diabetes, hypertension, hyperlipidemia, and atrial fibrillation with patent foramen ovale on apixaban. She had no family history of thyroid cancer and no radiation exposure. Thyroid nodules were found incidentally, and she denied compressive symptoms. She had annual surveillance for the past 4 years, and her latest thyroid US redemonstrated 4 solid, hypoechoic nodules. The largest nodule, previously biopsied and benign in 2020, remained stable on the right. The next largest nodule in the left mid-thyroid was now 1.1 x 0.8 x 0.9 cm—a 30% growth from the previous year—with new punctate echogenic foci consistent with the TIRADS 5 classification. This finding was shared with the patient, who favored investigating with an FNA. At the recommendation of her PCP and the performing provider, she held her apixaban for approximately 48 hours before the FNA procedure.The US-guided thyroid FNA biopsy was uneventful, and the results indicated a benign nodule. However, 4 hours post-procedure, the patient suddenly became unresponsive while in the middle of cooking dinner. She was taken to the ED and found to have an ischemic stroke by basilar embolism, attributed to her interruption in apixaban therapy. Tenectaplase led to initial improvement but had subsequent hemorrhagic transformations affecting the midbrain, thalamus, and pons. This marked the beginning of a complex 2-month hospitalization requiring tracheostomy and percutaneous endoscopic gastrostomy (PEG) placement, followed by nearly a year of physical, occupational, and speech rehabilitation. Despite these efforts, she has not been able to return to her pre-stroke level of function and independence. Discussion: There is no consensus on the safety of performing a thyroid fine needle aspiration (FNA) biopsy for patients on blood thinner medications. Providers who favor holding blood thinners before FNA cite concerns for post-procedural hematoma formation or increased risk of non-diagnostic results. However, there is less discussion about the risks of interrupting these medications. This case emphasizes the potential for severe consequences from interrupting medically-indicated blood thinner therapy. The temporary discontinuation of apixaban for a routine thyroid FNA led to a life-threatening thrombotic event in our patient’s case. This outcome highlights the importance of carefully weighing the risks and benefits of medication interruptions for vulnerable populations. Further study is needed to investigate the safety of thyroid FNA on uninterrupted blood thinner therapy. Presentation: 6/2/2024