Undiagnosed diabetes: prevalence, risks and solutions

  • 29 June 2021

What complications does undiagnosed diabetes cause, and what is the role of optometrists in detecting and preventing this condition? Kathy Oxtoby reports.

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More than 4.9 million people in the UK are currently living with diabetes. An additional 13.6 million people are at an increased risk of type 2 diabetes in the UK, while 850,000 people are currently living with type 2 diabetes but are yet to be diagnosed. Cases of diabetes in the UK have doubled in the last 15 years (Diabetes UK, 2021a). 

Those identified as being at high risk of type 2 diabetes are sometimes referred to as having “pre-diabetes”. “This means that your blood sugar levels are higher than usual, but not high enough for you to be diagnosed with type 2 diabetes,” says Natasha Marsland, Senior Clinical Adviser at Diabetes UK. But following a healthy diet and being active are just some of the steps people can take to prevent or delay type 2 diabetes from developing, she says.

Sight loss and risk factors 

Diabetes is the leading cause of preventable sight loss in the UK (Diabetes UK, 2021b). If it is not managed appropriately, it can lead to serious complications, including eye problems. Diabetic retinopathy (DR) occurs when blood sugar levels are consistently high due to diabetes either being undiagnosed or poorly controlled and, if left untreated, can lead to sight loss.

Obesity is the single greatest risk factor, and accounts for 80% to 85% of someone's risk of developing the condition (Diabetes UK, 2021a).

While diet, physical activity and weight loss can help reduce the risk of developing type 2 diabetes, some risk factors can’t be changed, such as age, ethnicity and a family history of diabetes. Risk increases for those over the age of 40 if they are white, and over the age of 25 if they are from African-Caribbean, Black African or South Asian backgrounds. People are also two to six times more likely to get type 2 diabetes if they have a parent, brother, sister or child with diabetes (Diabetes UK, 2021c). 

The symptoms of diabetes include needing to urinate more often, being thirsty, tiredness and weight loss. “While the symptoms of type 1 diabetes can develop quickly, type 2 diabetes symptoms often develop more slowly, and can sometimes go undetected for up to 10 years,” says Natasha. 

Missed diagnoses during pandemic
During the pandemic, some people may have been “reluctant to seek medical help, thinking that their symptoms were not ‘serious’ enough”, says Natasha. Recent research found that up to 60,000 diabetes diagnoses may have been missed or delayed during the pandemic (Carr et al, 2021).

Daniel Hardiman-McCartney FCOptom, Clinical Adviser for the College, says people may be averse to seeking medical help if they think they might have diabetes, or reluctant to accept a diagnosis. “There’s is unfortunately a stigma attached to this condition,” he says, “which is seen as a lifestyle disease, which can act as a barrier to effective management. .”

For optometrists, a strong predictive sign that their patient has diabetes when they examine the back of the eye using a slit lamp biomicroscope is to find DR or maculopathy, says Daniel. He advises photographing the back of the eye, and magnifying and changing the image from colour to black and white to identify more easily any retinal haemorrhages or exudates, which indicate the early stages of retinopathy (R1).

Taking a thorough history can also help optometrists identify definitive or borderline symptoms of diabetes, says Daniel.

Sensitivity is key when taking a patient’s history. “It’s appropriate to ask if they smoke, which is a risk factor. But with risk factors such as weight it is tactful to ask if the patient has a good balanced diet,” says Daniel. “What isn’t helpful is telling people to go on a diet, diabetologists or specialist nurses and dietitians have the expertise in this field. The advice you give should be constructive, aligned with local interdisciplinary advice and always blame-free.”

Advocating a healthy lifestyle, encouraging people to get regular eye tests, and signposting people to resources are also ways in which optometrists can support the management and prevention of diabetes.

Daniel says: “Optometrists have an important health role beyond eye care. Diabetes, which is one of the largest health burdens on society, is a salient example of where we can help detect  a systemic health condition.”

If you suspect someone may have diabetes or is at risk of developing diabetes:

  • Refer patients to their GP for further testing and access to support or prevention programmes 
  • Refer patients to their ophthalmology department if they have grade 2 or 3 retinopathy at the appropriate urgency 
  • Supply imaging via NHS.net to eye clinics if possible, if you believe the case could be sight-threatening.

Case study

Nancie Edwards MCOptom, an optometrist for Specsavers, Cardiff, reflects on her experience of referring a patient who had poor diabetic control.
Earlier this year, a patient came to my practice for a routine eye test. He had type 2 diabetes, which he said was being managed through diet and exercise. Closer examination revealed he had extensive background DR.

Fortunately it wasn’t proliferative DR, which would have needed urgent hospital intervention. We agreed he needed to improve his current diabetic control. I referred him back to his GP – requesting a diabetic review – and arranged a six-week follow-up appointment.  
At his next appointment, and now taking metformin for his diabetes prescribed by his GP, I was expecting to see some improvement. However, his DR was worse, so I referred him to an ophthalmologist to see if an intervention was required. Hopefully he will receive the appropriate treatment.
During the pandemic I’ve seen more cases of extensive DR, and more people whose diabetes is not being managed, and sometimes not even diagnosed. This could be because people have not been accessing their primary care provider during this crisis, screening services may have been cancelled, or patients have been gaining weight.
It is therefore crucial for optometrists to be extra cautious during consultations with patients who have, or are at risk of diabetes, to take a thorough history, and to advise that poor diet and lifestyle can have a detrimental impact on eye health. 

  • Diabetic retinopathy – decision-making and management: https://learning.college-optometrists.org/enrol/index.php?id=257
  • Getting referrals right: https://learning.college-optometrists.org/enrol/index.php?id=193
  • College Guidance – Examining people with diabetes mellitus: https://guidance.college-optometrists.org/guidance-contents/knowledge-skills-and-performance-domain/examining-patients-with/?searchtoken=Diabetes
  • College Guidance – Urgency of referral guidance: https://guidance.college-optometrists.org/guidance-contents/annexes/annex-4-urgency-of-referrals
  • Diabetes UK helpline: 0345 123 2399
  • Diabetes UK education and information for patients: https://www.diabetes.org.uk/professionals/information-support-for-your-patients/education-information
  • Diabetes UK’s free online Know Your Risk tool. Patients can find out their risk of developing type 2 diabetes, and how to reduce it: https://riskscore.diabetes.org.uk/start
  • NHS Healthier You NHS Diabetes Prevention Programme: https://preventing-diabetes.co.uk



Kathy Oxtoby

Carr M J, Leelarathna L, Thabit H et al. (2021) Impact of Covid-19 on diagnoses, monitoring, and mortality in people with type 2 diabetes in the UK. The Lancet Diabetes & Endocrinology 9(7): 413-5.

Diabetes UK. (2021a) Diabetes diagnoses double in the last 15 years. (accessed 22 June 2021)

Diabetes UK. (2021b) Diabetes and eye problems (diabetic retinopathy). (accessed 22 June 2021).


Diabetes UK. (2021c) Diabetes risk factors. See: https://www.diabetes.org.uk/preventing-type-2-diabetes/diabetes-risk-factors (accessed 22 June 2021)