Excessive exogenous thyroid hormone ingestion may lead to severe thyrotoxicosis and cause potential harm. We have reviewed the literature and suggested that thyroid hormone supplementation should not be used to alleviate nonspecific complaints in patients with normal endogenous thyroid function. Failure to do so may cause serious harm, as demonstrated in one of the cases described here. In addition, treatment based on symptom relief only without biochemical measure may lead to overmedication – as reported from academic hospitals both in Canada and the United States. Given the risk of severe thyrotoxicosis from potential compounding errors, pharmacies providing a compounding service should be subject to more rigorous monitoring by the food and drug administration. Clinicians should also use local biochemical markers when titrating thyroid hormone supplements even though the normal thyroid function reference range has its limitation, failure to do so may result in iatrogenic thyrotoxicosis.Copyright © 2020 He ZH, Li Y, Trivedi N, Gill S, Hennessey JV.