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Important reminder: nitrous oxide (N2O) as a cause of functional vitamin B12 deficiency
  1. Abdullahi Elsheikh Mahgoub,
  2. Smit Sunil Deliwala and
  3. Ghassan Bachuwa
  1. Internal Medicine, Hurley Medical Center, Flint, Michigan, USA
  1. Correspondence to Dr Ghassan Bachuwa; gbachuw2{at}


A 32-year-old woman who misused multiple substances, including nitrous oxide (N2O), sought medical advice after she subacutely developed bilateral lower extremity weakness without a sensory level but with ataxia—her significant other developed similar symptoms with vitamin B12 deficiency due to N2O intake. Laboratory results revealed macrocytic anaemia despite normal B12 and folate levels, with serum markers pointing towards functional cobalamin deficiency. Spinal MRIs and cerebrospinal fluid analysis were unremarkable. Our patient was treated with vitamin B12 supplementation with an encouraging response.

  • neurology (drugs and medicines)
  • neurology
  • vitamins and supplements
  • drugs misuse (including addiction)

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  • Twitter @abadmahgoub, @smitdeliwalaMD

  • Contributors AEM: conception, design, draft and review. SSD: acquisition and review. GB: draft and review.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.