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Background: Subclinical hypothyroidism is an entity based on the laboratory findings of a raised serum thyrotrophin (TSH) concentration and a normal free thyroxine (FT4) concentration. Patients with subclinical hypothyroidism who also have anti-thyroid peroxidase (TPO) antibodies have a higher conversion to overt hypothyroidism than those without, and treatment with thyroxine is recommended. Method: We audited anti-TPO assay requests within two NHS Trust hospitals, against consensus standards, to ascertain whether a cascade approach to anti-TPO testing and direct advice leads to more appropriate prescribing of thyroxine in general practice. Results: Our data show that where anti-TPO status was automatically tested for and clear advice for treatment given, >85% of patients were treated according to the standard required by the consensus document, with >90% of those recommended to be commenced on thyroxine actually doing so. In contrast, where anti-TPO was not routinely assessed, treatment was started in 46% of patients, without clear evidence that this was appropriate. Conclusion: In order to better advise clinicians and in accordance with the agreed protocol, laboratory-generated cascade testing for anti-TPO antibodies should be an integral part of the investigation of subclinical hypothyroidism, and reports should contain appropriate interpretation and advice.