Errors by machines used to diagnose diabetes mean at least 55,000 people in England will need further blood tests, a BBC investigation has discovered.

Some patients have been wrongly diagnosed with type 2 diabetes and even prescribed medication they don’t need – and there could be more people affected, say NHS England.

NHSE has confirmed 16 hospital trusts use the machines, made by Trinity Biotech, which have produced inaccurate test results.

In a statement, Trinity Biotech says it is working closely with the UK health regulator and has contacted all hospitals which use the machines.

The BBC first reported in September 2024 that 11,000 patients faced re-testing after a machine at Luton and Dunstable Hospital issued incorrect diabetes results.

NHS England now say type 2 diabetes diagnoses rose by 10,000 in 2024, 4% more than expected.

The procedure, known as the haemoglobin A1C test, measures average blood sugar levels which are used to diagnose type 2 diabetes and monitor the condition.

According to the medicines and healthcare regulator (MHRA), issues with the tests on these machines was first reported in April 2024.

The BBC has asked NHS England to confirm which trusts are affected.

Vicky Davies, 36, from Kingston upon Hull was first told she had type 2 diabetes in October 2024.

She was advised to try and lose weight first, sent for eye screening and was later prescribed what she understands was the maximum dose of the diabetes drug metformin.

In April 2025 she had further blood tests as part of her three month review and was told that she wasn’t diabetic, which she assumed was because she had been on metformin.

Later that month though, she was told her blood results might not have been accurate and advised to come off the medication immediately.

During the four months she took metformin she suffered with stomach issues and dizziness and still feels stressed.

“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,” she told BBC News.

In a letter, Vicky’s GP practice told her they were not aware of the problems occurring in the laboratories, adding that they work to the best of their ability with the medical information available.

The NHS trust which runs diabetes tests for Hull says it has stopped using the kit in question,

“We understand this situation may have caused concern and apologise for any worry or anxiety,” said a spokesperson for York and Scarborough Teaching Hospitals NHS Foundation Trust.

In September 2024, a message on the Bedfordshire trust website said 11,000 patients needed to be re-tested.

It warned some of them could have been misdiagnosed with type 2 diabetes as a result of problems with tests analysed at the hospital’s laboratory.

The trust apologised “for any emotional distress and inconvenience”.

In July 2025, the Medicines and Healthcare products Regulatory Agency said it had received reports describing a positive bias delivered by the Trinity Biotech machines.

This resulted in some patients being incorrectly diagnosed as pre-diabetic or diabetic.

NHS trusts are already recalling patients for repeat tests and NHS England says anyone who needs a repeat test will be contacted by their GP or local hospital.

It adds that, for people who may have been wrongly diagnosed as a result of this issue, the risk is low and they would be given lifestyle advice and offered support programmes first.

Metformin, which may have been mistakenly prescribed for some of these patients, works by lowering blood sugar levels by improving the way the body handles insulin.

If you experience these symptoms whilst taking diabetes medication:

• hypoglycaemia (shaking/trembling, sweating, confusion, loss of consciousness)
• and hyperglycaemia (excessive thirst, blurred vision, recurrent infections)

The advice is to seek medical attention immediately.

Prof Kamila Hawthorne, chair of the Royal College of GPs, said that while “errors can and do happen… the prospect of widespread technology failures like this will be of huge concern for all GPs, primarily because of the unnecessary distress, inconvenience and anxiety they can cause our patients.”

Prof Hawthorne said the priority was to minimise the impact on patients but there would also be a significant impact on GPs’ workload and they would need support.

Dr Clare Hambling, diabetes national clinical director for NHS England, said potential misdiagnosis of a long-term condition like type 2 diabetes “is understandably worrying, however the clinical risk of harm to patients following this issue is low”.

NHS England says fewer than 10% of their laboratories were affected and all have either replaced the machines or addressed calibration issues.

In response to an inquiry from the BBC, Trinity Biotech said: “The company has worked closely with the MHRA to resolve the issues experienced by some UK labs using the system.”

The statement also said the company had “issued three Field Safety Notices in 2024 to all UK users, informing them of a potential positive bias issue.”

These notices included “reiteration of details of the actions to be taken to ensure optimum operation of the system, with an emphasis on the importance of operating the system per the manufacturer’s instructions,” the statement continued.