Subacute combined degeneration (SCD) is myelopathy caused by vitamin B12 deficiency, leading to demyelination of the dorsal column located in the posterior spinal cord. Despite the high prevalence of recreational nitrous oxide use, its detrimental effects, including significant nerve dysfunction, are insufficiently recognized. We present the case of a 32-year-old male who was brought to the emergency department with complaints of paresthesia of his four extremities and lower extremity weakness. He was found to have B12 deficiency from chronic nitrous oxide abuse and responded positively to intramuscular B12 supplementation. It is important to consider possible nitrous oxide abuse while investigating suspected B12 deficiency, especially in patients presenting with nonspecific myeloneuropathy. Elevated methylmalonic acid (MMA) level is specific for diagnosing B12 deficiency. Prompt diagnosis and treatment can lead to the resolution of the symptoms and prevent further nerve damage.