Thyroid disorders are prevalent in the general population affecting approximately 5-10%, with a higher incidence of hypothyroidism compared to hyperthyroidism. Clinical symptoms of hypothyroidism are often non-specific including muscular manifestations, which can vary from myalgia, fatigue, and cramping, occurring in up to 70% of cases. However, rhabdomyolysis, the rapid breakdown of skeletal muscle, is a rare manifestation, often triggered by a precipitating factor. We present a case of a 25-year-old man with a known history of Hashimoto's thyroiditis who presented with symptoms of rhabdomyolysis complicated by renal impairment secondary to severe overt hypothyroidism in the context of medication non-compliance. Our patient presented with symptoms of generalised myalgia, cramping and generalised muscle fatigue. Physical examination revealed generalised muscle tenderness with intermittent cramping. Laboratory investigations were consistent with severe overt hypothyroidism with TSH 531.4mIU/L and free-T4 0.9pmol/L. Creatine kinase (CK) levels were elevated 1052U/L with associated acute renal impairment creatinine 129umol/L. There were no other identifiable precipitating factors for rhabdomyolysis and renal impairment. Our patient was managed with prompt recommencement of thyroxine therapy and intravenous hydration. Over the course of hospitalisation, the patient's myalgias gradually improved, with improvement in CK levels and renal function. Our case highlights the potential consequences of prolonged non-compliance with thyroxine replacement therapy in patients with Hashimoto's thyroiditis, highlighting a rare but significant complication of rhabdomyolysis and associated renal impairment. Clinicians should remain vigilant in monitoring patients' adherence to prescribed medications and be aware of the possible complications arising from non-compliance. Early recognition and prompt management of such cases can lead to successful recovery and prevent long-term sequelae.