Iatrogenic copper deficiency: risks and cautions with zinc prescribing

Aims
Copper deficiency resulting from prescribing zinc in high doses is a rare but life-changing diagnosis that is frequently overlooked. The aim of this study is to gauge how often zinc-induced copper deficiency is missed, to raise awareness of the condition and to stress the need for guidelines for prescribing zinc.

Methods
Suspected cases of zinc-induced copper deficiency were retrospectively obtained by selecting those patients with hyperzincaemia and hypocupraemia from the database of the Scottish Trace Element Laboratory. Case records were reviewed to determine the validity of the suspected diagnosis.

Results
After exclusions, 23 instances of high serum zinc and low serum copper concentrations were found. A positive diagnosis of zinc-induced copper deficiency was made in 14 patients of which 7 (50%) were previously undiagnosed.

Conclusion
Serum zinc and copper concentrations are rarely measured in patients prescribed zinc and so the vast majority of cases of zinc-induced copper deficiency are likely to be undiagnosed. We recommend the current official advice on the dose and frequency of zinc administration is revised in order to limit, and potentially eradicate, the condition.