Thirlwall Inquiry recommends adoption of laboratory insulin testing guidance

The final report of the Thirlwall Inquiry, established to examine events at the Countess of Chester Hospital between 2015 and 2018, published its final report on 15 September 2026. Among its recommendations is that the Getting It Right First Time (GIRFT) guidance, Laboratory handling of insulin requests in the investigation of hypoglycaemia, should be made mandatory and applied nationally.

Published in October 2025, the guidance was developed through NHS England's GIRFT programme with the involvement of professional organisations including the IBMS, Association for Laboratory Medicine, Royal College of Pathologists and British Association of Perinatal Medicine.

The guidance sets out best practice for the measurement, reporting and timely communication of insulin and C-peptide results, particularly where elevated insulin is detected alongside low C-peptide. It covers the full diagnostic pathway, from sample collection and laboratory receipt through to analysis, interpretation and communication of results.

A critical red flag for laboratories

Central to the guidance is the identification of hypoglycaemia with elevated insulin and low C-peptide as a red flag scenario.

It states that laboratories must have mechanisms in place to identify this combination rapidly and that relevant medical consultants should be informed immediately.

The guidance also makes a series of recommendations for laboratory practice, including ensuring that glucose and C-peptide are measured alongside insulin in the investigation of hypoglycaemia, understanding the characteristics and limitations of insulin assays, and establishing robust processes for interpreting and communicating clinically significant results.

For unexplained results, the guidance says they should be communicated urgently to the consultant responsible for the patient, with the communication recorded within the LIMS.

Thirlwall Inquiry recommendation

The Inquiry specifically considered the handling of insulin and C-peptide results. Its final recommendations state that the October 2025 GIRFT guidance for testing and reporting insulin and C-peptide results must be made mandatory and of national application.

The Inquiry also welcomed the guidance's requirement for local protocols around high insulin and low C-peptide results and suggested consideration should be given to developing a single step-by-step template protocol for responding to such findings.

The recommendation reinforces the importance of biomedical scientists and the wider laboratory team in recognising potentially significant findings and ensuring they are interpreted and communicated appropriately.

The GIRFT guidance itself calls on laboratories to:

embed its recommendations into routine practice, undertake periodic audits and establish an agreed local policy covering the pathway from request through to interpretation and communication of results.

IBMS members working in clinical biochemistry are encouraged to review the guidance and consider how its recommendations are reflected in their local procedures.

Read the guidance: Laboratory handling of insulin requests in the investigation of hypoglycaemia

Read the Thirlwall Inquiry recommendations: Chapter 45 – Recommendations, Thirlwall Inquiry