London Medical Diabetes
Glucose tolerance test
London Medical provides the most up-to-date procedures for patients – with clinics held by some of the UK’s most renowned specialists.
Catching the early signs of diabetes can make a real difference to your health. Our oral glucose tolerance test shows how your body processes sugar, helping us offer early, personalised support when it matters most.
The OGTT is a simple, well-established test that helps diagnose conditions such as type 2 diabetes, prediabetes, insulin resistance (when your cells don’t respond well to insulin) and gestational diabetes (diabetes during pregnancy). With clear results, we can help you take proactive steps to protect your long-term health.
What is an oral glucose tolerance test?
An oral glucose tolerance test measures how well your body can process the sugar you get from food and drinks.
After a period of fasting (where you don’t eat or drink for several hours), you’ll be asked to drink a glucose-rich solution. We then take blood samples at set times to see how your blood glucose levels rise and fall.
When you eat carbohydrates (like bread, pasta and fruit), your body breaks them down into glucose (sugar), which you use for energy. To make sure you don’t have too much or too little glucose in your blood, your body releases a hormone called insulin to regulate your blood glucose levels.
An OGTT helps us understand how well your body produces and uses insulin and checks if your blood glucose levels are within the normal range.
At London Medical, we use the OGTT as part of a broader approach to personalised care. Your results help us design a management or support plan that works for you, whether that involves lifestyle changes, medication or further testing.
Why is an OGTT important?
The OGTT is one of the most sensitive tests available for detecting early changes in glucose tolerance. Identifying these changes early allows for timely action, reducing the risk of long-term health problems linked to high blood glucose.
Screening for gestational diabetes
If you’re pregnant, an OGTT may be recommended between 24 and 28 weeks to check for gestational diabetes. Managing this condition early is vital to ensure both your health and the health of your baby during and after pregnancy.
Early detection of prediabetes and insulin resistance
The OGTT can identify problems with how your body processes glucose even before diabetes develops. Catching insulin resistance or prediabetes early means you can make simple lifestyle changes that may delay or prevent the onset of type 2 diabetes.
Tailored treatment and support plans
Your OGTT results help us understand exactly how your body is responding to glucose. This allows for more personalised guidance, from dietary advice and exercise plans to targeted medication or further assessment.
A proactive approach to prevention
The test is also useful if you’re focused on preventing diabetes. It can confirm whether you’re at risk of developing diabetes and related complications, as well as help you make informed decisions about your health before symptoms appear.
Who should consider an OGTT?
You might be referred for an OGTT for several reasons – either as part of routine screening or because you’re showing possible signs of a glucose processing issue.
You may benefit from an OGTT if:
- you have a family history of diabetes
- you are overweight or have a sedentary (inactive) lifestyle
- you are pregnant and have been advised that you may be at risk of gestational diabetes
- you are experiencing symptoms such as excessive thirst, frequent urination, blurred vision or unexplained tiredness
- you’ve had slightly abnormal blood sugar readings in the past
In some cases, you may not notice any symptoms at all. That’s why the OGTT can be particularly helpful – catching early changes before they develop into diabetes.
What to expect during the test
Before your appointment, you’ll be asked to fast for 8 to 10 hours. You can still drink water during this time, but you should avoid food, sugary drinks and strenuous exercise. It’s important to follow this guidance to ensure your results are accurate.
When you arrive, we’ll take an initial blood sample to measure your baseline (fasting) blood sugar level. This gives us a starting point to compare how your body reacts to the glucose drink.
You’ll then be given a sweet glucose solution to drink. Some people find it very sugary, but it’s important to drink it all within a few minutes.
Over the next two hours, we’ll take one or more blood samples at regular intervals – usually at the one-hour and two-hour marks. These samples show how your blood sugar changes over time as your body processes the glucose.
You’ll be asked to stay seated and avoid any physical activity during this time, as movement can affect your blood sugar and influence the results.
The whole process usually takes between two and three hours. Afterwards, you can eat and return to your normal activities unless advised otherwise by your clinician.
Understanding your results
Your results will be reviewed by one of our experienced specialists, who will talk you through what they mean and what steps to take next.
Your OGTT test results can show:
- normal glucose tolerance – which means your blood sugar rises and falls within the expected range
- prediabetes – diagnosed when your glucose levels are higher than normal but not high enough for a diagnosis of diabetes
- diabetes – confirmed if your blood glucose levels remain too high at certain points of the test
These results provide a clear foundation for personalising the next steps in your healthcare journey. This might include making changes to your diet or activity levels, further testing or starting treatment.
Why choose London Medical for your OGTT?
At London Medical, we offer more than just a test. We offer support, clarity and expert care every step of the way.
Our clinic is designed to make your visit as comfortable and efficient as possible. You’ll be welcomed by a friendly team who will explain what to expect and make sure you’re relaxed throughout the process.
Your results are analysed by our experienced endocrinologists and diabetes specialists. If your results show anything that might need a closer look, we can arrange follow-up care straight away, with access to dietitians, lifestyle coaches, consultants and other in-house services all under one roof.
With our central London location, flexible appointment times and personalised support, we make managing your health accessible.
Book your oral glucose tolerance test today
Taking control of your health starts with understanding how your body works. If you’ve been referred for an oral glucose tolerance test or if you’re experiencing symptoms and want to have them investigated, we can help.
Call us on +44 (0)207 467 5470 or email bookings@londonmedical.co.uk to schedule your appointment.
Frequently Asked Questions
Our Consultants
Dr Ralph Abraham
Dr Ralph Abraham, a founder of London Medical, specialises in diabetes, weight management, endocrinology and cholesterol.
Dr Rakesh Amin
Clinical lead for endocrinology and diabetes at Great Ormond Street Hospital. His clinical practice encompasses all areas of paediatric and adolescent endocrinology and diabetes.
Dr David Cavan
An experienced consultant endocrinologist with expertise in all areas of diabetes management.
Dr Harvinder Chahal
With a focus on adults, Dr Chahal is a consultant in endocrinology, diabetes, bariatric medicine, and general internal medicine at Imperial College Trust.
Dr Claire Chalmers-Watson
Dr Chalmers-Watson is an experienced General Practitioner with over two decades of experience in primary care and a profound expertise in managing a broad spectrum of health conditions.
Dr Mimi Z. Chen
Specialist consultant in diabetes and endocrinology with a particular interest in weight loss and weight management medications.
Professor Pratik Choudhary
Consultant in diabetes with a special interest in type 1 and technology to manage it.
Dr Ling Ling Chuah
Consultant endocrinologist with over a decade’s experience in the treatment of diabetes.
Dr Andrew Frankel
Consultant nephrologist who specialises in the management of people with both chronic kidney disease and diabetes.
Ms Symone Genevezos
A passionate and dedicated dietitian offering nutrition and support for clients of all ages.
Our Locations
London Medical is located in the Harley Street medical area. Together with top experts across a range of multi-disciplinary fields, we offer the finest facilities for your care, all under one roof.
Monday to Friday 8.30am to 8pm
Monday to Friday 8.30am to 8pm
Monday to Friday 8.30am to 8pm
Speak to a member of our team
Contact the appointments team
If you have any questions or want to book an appointment, please speak to our team on +44 (0)800 0483 330.
Or, make an enquiry online using this form and one of our team will be in touch. Please note, all the information collected is required as part of our registration process. By using this form you agree with the storage and handling of your data by our team. You don't need a referral from your GP to make an appointment with us.