Thousands of NHS patients across England have been caught up in a medical testing controversy, after it emerged that faulty blood testing machines led to widespread misdiagnoses of type 2 diabetes. According to NHS England, at least 55,000 patients will now need their blood tests repeated, following revelations that machines made by US and Ireland-based manufacturer Trinity Biotech produced inaccurate results at one in ten NHS laboratories. The scale of the issue, affecting 16 hospital trusts, has left many patients grappling not only with unnecessary medication but also with the emotional turmoil of a mistaken diagnosis.
The problem first came to light in 2024, when the Bedfordshire NHS Foundation Trust acknowledged that some patients at Luton and Dunstable Hospital may have received higher than accurate blood glucose readings. As reported by BBC News, the trust issued an apology "for any emotional distress and inconvenience," but the extent of the problem would only become clear months later. By September 2025, NHS England confirmed that thousands of people might have been prescribed medicines—such as Metformin, a commonly used diabetes drug—that they did not actually need.
For patients like Vicky Davies, a 36-year-old from Kingston upon Hull, the impact was deeply personal. She shared her story with BBC News, explaining, "It's had a huge effect on my life. Since the diagnosis I have suffered with stress and had to take time off work to attend appointments. I've complained to my GP, but I didn't really get an apology. I'm just so angry." Davies was diagnosed with type 2 diabetes in October 2024 and spent six months on the strongest dose of Metformin before the error was discovered. During that time, she endured not only the psychological burden of a chronic illness but also the physical side effects of a drug she never needed. Metformin, while effective at lowering blood sugar by improving the body’s handling of insulin, can cause side effects such as shaking, sweating, confusion, loss of consciousness, excessive thirst, blurred vision, and recurrent infections.
The faulty readings stemmed from errors in the haemoglobin A1C test, a standard procedure that measures average blood sugar levels and is used both to diagnose and monitor type 2 diabetes. The Medicines and Healthcare products Regulatory Agency (MHRA) first flagged concerns about the accuracy of these machines in April 2024, prompting a series of investigations. By September 2024, BBC News was reporting that 11,000 patients faced re-testing after the initial problems were discovered at Luton and Dunstable Hospital.
Trinity Biotech, the company behind the affected machines, has maintained that it is working closely with UK health authorities to address the problem. In a statement quoted by The Independent and BBC News, the firm said, "The company has worked closely with the MHRA to resolve the issues experienced by some UK labs using the system." Notably, Trinity Biotech issued three Field Safety Notices in 2024 to all UK users, warning of a "potential positive bias issue" and reiterating the importance of following the manufacturer's instructions for optimal operation. The company also confirmed that it had contacted all hospitals using the machines and continues to cooperate with the MHRA to ensure the situation is fully resolved.
Dr Clare Hambling, NHS England’s national clinical director for diabetes, sought to reassure the public, acknowledging the seriousness of the situation but emphasizing that the "clinical risk of harm to patients following this issue is low." She explained, "Being potentially misdiagnosed with any long-term condition, such as type 2 diabetes, is understandably worrying, however the clinical risk of harm to patients following this issue is low." Dr Hambling also confirmed that less than 10 percent of NHS laboratories were affected and that all have either replaced the problematic machines or addressed calibration issues following MHRA advice issued in July 2025. "All laboratories have either replaced the machines or addressed calibration issues following MHRA advice in July—and anyone requiring a repeat test will be contacted by their GP or local hospital," she added.
For many, the ordeal has highlighted the fragility of trust in diagnostic technology and the ripple effects of even a small error rate in a vast health system. While the majority of NHS laboratories were not impacted, the sheer number of affected patients—tens of thousands—has raised questions about oversight, communication, and the speed of response. The MHRA, for its part, has been criticized in some quarters for not identifying the issue sooner, although it maintains that it acted promptly once the problem was reported in April 2024.
The emotional and practical consequences for patients cannot be understated. Beyond the shock and anxiety of a false diagnosis, many have had to contend with the side effects of unnecessary medication, missed work, and the inconvenience of repeated medical appointments. For some, like Vicky Davies, the lack of a direct apology from their GP has only compounded the frustration. The situation has also forced a reckoning within the NHS about how to better communicate with patients when errors occur and how to ensure that similar incidents are caught earlier in the future.
The haemoglobin A1C test, central to this controversy, is a cornerstone of diabetes management worldwide. It provides a snapshot of average blood sugar levels over several months and informs crucial decisions about medication and lifestyle changes. When the test is compromised, as it was in this case, the consequences can be far-reaching—not just for individuals, but for the credibility of the entire health system.
Trinity Biotech’s response—issuing safety notices, working with regulators, and reiterating the importance of proper machine operation—reflects the complexities of managing medical technology on a national scale. The company’s cooperation with the MHRA has been described as "close," but some patient advocates argue that more needs to be done to restore public trust and ensure accountability.
Looking ahead, NHS England has pledged to contact all patients who require repeat tests, with GPs and local hospitals reaching out directly. The health service has also moved to reassure the public that all affected laboratories have now resolved the calibration issues or replaced the faulty machines. For the vast majority of patients, the clinical risk remains low, but the psychological scars of a misdiagnosis may linger far longer.
This incident serves as a sobering reminder of the critical importance of accuracy in medical testing—and the human cost when technology falls short. As the NHS and Trinity Biotech work to put things right, patients and clinicians alike will be watching closely, hoping that lessons learned from this episode will prevent future mishaps and restore confidence in the systems designed to keep us healthy.
