Article Text

Download PDFPDF
Case report
When thyroid labs do not add up, physicians should ask patients about biotin supplements
  1. Michael S Lundin1,2,
  2. Ahmad Alratroot1,2,
  3. Fawzi Abu Rous1,2 and
  4. Saleh Aldasouqi2,3
  1. 1Internal Medicine, Michigan State University, East Lansing, Michigan, USA
  2. 2Sparrow Hospital, Lansing, Michigan, USA
  3. 3Endocrinology, Michigan State University, East Lansing, Michigan, USA
  1. Correspondence to Dr Michael S Lundin; makala.lundin{at}


A 69-year-old woman with a remote history of Graves’ disease treated with radioactive iodine ablation, who was maintained on a stable dose of levothyroxine for 15 years, presented with abnormal and fluctuating thyroid function tests which were confusing. After extensive evaluation, no diagnosis could be made, and it became difficult to optimise the levothyroxine dose, until we became aware of the recently recognised biotin-induced lab interference. It was then noticed that her medication list included biotin 10 mg two times per day. After holding the biotin and repeating the thyroid function tests, the labs made more sense, and the patient was easily made euthyroid with appropriate dose adjustment. We also investigated our own laboratory, and identified the thyroid labs that are performed with biotin-containing assays and developed strategies to increase the awareness about this lab artefact in our clinics.

  • endocrine system
  • skin
  • thyroid disease
  • general practice / family medicine
  • vitamins and supplements

Statistics from


  • Contributors MSL wrote the manuscript. AA and FAR edited the manuscript and made substantial changes. SA is the attending endocrinologist who reviewed this case.

  • 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 For SA Abbott Diagnostics (Consultant), since October 2019. Related to biotin interference with labs. This COI is recent and it started after we began writing the case up. The company approached SA given his prior published work on biotin.The other authors have no competing interests.

  • Patient consent for publication Obtained.

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

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.