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The risk of copper deficiency in patients prescribed zinc supplements
  1. Andrew Duncan1,
  2. Calum Yacoubian2,
  3. Neil Watson3,
  4. Ian Morrison4
  1. 1Scottish Trace Element and Micronutrient Reference Laboratory, Glasgow Royal Infirmary, Glasgow, UK
  2. 2Department of Paediatric Surgery, Yorkhill Hospital, Glasgow, UK
  3. 3Department Biochemistry, Edinburgh Royal Infirmary, Little France, Edinburgh, UK
  4. 4Department of Neurology, Ninewells Hospital, Dundee, UK
  1. Correspondence to Dr Andrew Duncan, Scottish Trace Element and Micronutrient Reference Laboratory, Glasgow Royal Infirmary, Castle St, Glasgow G4 0SF, UK; Andrew.duncan{at}ggc.scot.nhs.uk

Abstract

Aims In high doses zinc may cause copper deficiency, a diagnosis that is often missed resulting in anaemia, neutropenia and irreversible neurological symptoms. The aim of this study was to assess if zinc deficiency is erroneously diagnosed by misinterpretation of plasma zinc concentrations and whether copper deficiency is induced in patients prescribed zinc.

Methods Casenotes of 70 patients prescribed zinc were scrutinised. Plasma concentrations of zinc, copper, C reactive protein and albumin were recorded from the laboratory database.

Results 62% of patients were prescribed zinc at doses sufficient to cause copper deficiency. In 48% of the patients, plasma zinc concentrations were low as a probable result of hypoalbuminaemia or the systemic inflammatory response rather than deficiency. Awareness of copper deficiency was lacking; it was only documented as a possible side effect in one patient and plasma copper was measured in only two patients prescribed zinc. 9% of patients developed unexplained anaemia and 7% developed neurological symptoms typical of copper deficiency.

Conclusions Zinc deficiency is frequently misdiagnosed on the basis of low plasma zinc concentrations. The potential risk of copper deficiency developing in patients prescribed high doses of zinc is apparently infrequently considered. It is probable that a significant minority of patients prescribed with high doses of zinc develop iatrogenic copper deficiency.

  • NEUROPATHIES
  • TOXICOLOGY
  • LABORATORY TESTS
  • HAEMATOLOGY

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