Diabetes
The different types of diabetes, how it is diagnosed, what you can do about it, and the checks that keep you well in the long term.
A diagnosis of diabetes, or being told you are at risk of it, can feel daunting. It is also a condition where what you know and what you do make a real difference. This guide covers the essentials, with most of the detail on type 2 diabetes and prediabetes, which are by far the most common.
What is diabetes?
Diabetes is a condition in which the level of glucose (sugar) in the blood is too high. Glucose comes from the food we eat and is the body's main fuel. Insulin, a hormone made by the pancreas, acts like a key that lets glucose move out of the blood and into cells. In diabetes, either there is not enough insulin, or the body does not respond to it properly, so glucose builds up in the bloodstream.
How common is it?
More than 5.8 million people in the UK are estimated to be living with diabetes, including well over a million who have type 2 diabetes but have not yet been diagnosed. Around 90% of cases are type 2.
Source: Diabetes UK.
Types of diabetes
Type 1
An autoimmune condition in which the immune system destroys the insulin producing cells of the pancreas. It is not caused by diet or lifestyle and cannot be prevented. It often starts in childhood or early adulthood but can begin at any age, usually comes on quickly over days or weeks, and always requires insulin.
Type 2
The body becomes resistant to insulin and, over time, the pancreas cannot make enough to compensate. It develops gradually, often over years. Risk is influenced by weight, particularly around the waist, family history, age, and ethnic background. People of South Asian, Black African, and Black Caribbean heritage are at higher risk and at a younger age.
Other forms include gestational diabetes, which develops during pregnancy and raises the lifetime risk of type 2 diabetes, and rarer types caused by single gene changes, pancreatic disease, or medicines such as steroids.
Symptoms
Type 2 diabetes often causes no symptoms for years and is frequently found on a routine blood test. When symptoms do occur, they include:
- Passing urine more often, especially at night
- Feeling very thirsty
- Feeling more tired than usual
- Losing weight without trying
- Recurrent thrush or genital itching
- Cuts and wounds that heal slowly
- Blurred vision
- Frequent skin or urine infections
Diagnosis & HbA1c
Diabetes is diagnosed with a blood test. The most commonly used is HbA1c, which reflects your average blood glucose over the previous two to three months. You do not need to fast for it.
| HbA1c | Older units | Result | What it means |
|---|---|---|---|
| Below 42 mmol/mol | Below 6.0% | Normal | No evidence of diabetes |
| 42 to 47 mmol/mol | 6.0 to 6.4% | Prediabetes | Higher than normal. A clear opportunity to prevent type 2 diabetes |
| 48 mmol/mol or above | 6.5% or above | Diabetes | Usually confirmed with a second test if you have no symptoms |
HbA1c can be unreliable in some situations, including pregnancy, some types of anaemia, certain inherited haemoglobin variants, and when diabetes has come on rapidly. In these cases a fasting glucose or other test is used instead.
Prediabetes
Prediabetes, formally called non diabetic hyperglycaemia, means your blood sugar is higher than normal but not yet in the diabetes range. It causes no symptoms. It is best thought of as an early warning rather than a diagnosis.
It is not inevitable. Large trials have shown that structured lifestyle change, with modest weight loss and regular activity, cuts the risk of progressing to type 2 diabetes by around half. Many people return to a normal HbA1c. We recommend a repeat blood test every year to keep track.
Sources: Diabetes Prevention Program (NEJM, 2002); Finnish Diabetes Prevention Study (NEJM, 2001).
Why control matters
Over years, raised blood glucose damages both large and small blood vessels. The risk of each of the complications below falls substantially with good control of blood sugar, blood pressure, and cholesterol.
Heart and circulation
Diabetes roughly doubles the risk of heart attack and stroke. Controlling blood pressure and cholesterol matters just as much as controlling blood sugar.
Eyes
Damage to the small vessels of the retina (retinopathy) can threaten sight. It is symptomless in its early stages, which is why screening is so important.
Kidneys
Diabetes is a leading cause of chronic kidney disease. Early changes are picked up with a simple urine test, long before symptoms develop.
Nerves and feet
Nerve damage can cause numbness, tingling, or pain in the feet. Combined with poorer circulation, small injuries can go unnoticed and heal slowly.
Lifestyle & remission
Lifestyle change is the foundation of managing type 2 diabetes at every stage, including for people who also take medication.
Weight
If you are carrying excess weight, losing even 5% of your body weight improves blood sugar, blood pressure, and cholesterol. Larger losses bring larger benefits.
Food
There is no single diabetes diet. Mediterranean style, lower carbohydrate, and other approaches can all work. The common threads are fewer refined carbohydrates and sugary drinks, more vegetables, pulses, and wholegrains, and a pattern you can sustain. Specially labelled diabetic foods are not needed.
Activity
Muscles use glucose when they work, and activity makes the body more sensitive to insulin for hours afterwards. Aim for 150 minutes of moderate activity a week, include some strength work, and break up long periods of sitting.
Can type 2 diabetes be reversed?
For many people, yes. Remission means blood sugar returning to the non diabetic range without diabetes medication. In the DiRECT trial (Lancet, 2018), a structured weight management programme in UK primary care achieved remission in 46% of participants at one year. Remission was closely tied to the amount of weight lost and is most likely in the first few years after diagnosis. It needs to be maintained, and regular checks should continue.
Medication
Type 2 diabetes tends to progress over time, so it is common to need medication, and to need more than one. The right choice depends on your blood sugar, weight, kidney function, heart health, and preferences. Many people are also offered a statin and blood pressure treatment to protect the heart and kidneys.
Metformin
Usually the first medicine for type 2 diabetes. It reduces the amount of glucose released by the liver and helps insulin work better. It does not cause weight gain or, used alone, low blood sugar. Nausea and loose stools are common at first, and are reduced by taking it with food, starting low, and using a slow release form.
SGLT2 inhibitors
Examples include dapagliflozin and empagliflozin. They help the kidneys pass excess glucose out in the urine, and have proven benefits for the heart and kidneys. Genital thrush is the most common side effect. They should be paused during any illness with vomiting, diarrhoea, or dehydration.
GLP-1 and related medicines
Examples include semaglutide and tirzepatide. Usually given as a weekly injection, they lower blood sugar, reduce appetite, and often lead to substantial weight loss. Nausea is common early on.
DPP-4 inhibitors
Examples include sitagliptin and linagliptin. Tablets with a modest effect and few side effects, often used when other options are unsuitable.
Sulfonylureas
Examples include gliclazide. They stimulate the pancreas to release more insulin. They work quickly but can cause low blood sugar and some weight gain.
Insulin
Essential from diagnosis in type 1 diabetes. In type 2 diabetes it may be needed if other treatments are no longer enough, which reflects the natural course of the condition rather than anything you have done wrong.
Sick day rules: If you are unwell with vomiting, diarrhoea, or a fever and cannot eat and drink normally, some medicines, including metformin and SGLT2 inhibitors, should be paused until you have been eating and drinking normally for 24 to 48 hours. Never stop insulin. Ask us for advice specific to your treatment.
Your regular checks
Most complications of diabetes can be prevented or caught early if you have the recommended checks. Everyone with diabetes should have the following at least once a year. Eye screening may be every two years if your previous results were clear.
- HbA1c, to see how your blood sugar has been over the past two to three months
- Blood pressure
- Cholesterol
- Kidney function, with a blood test and a urine test for protein
- Foot examination, checking sensation and circulation
- Eye screening, using photographs of the back of the eye
- Weight and waist measurement
- A review of your medication, smoking status, and emotional wellbeing
Between checks, look at your feet regularly and tell us promptly about any cut, blister, or sore that is not healing, or any change in colour or sensation. People with diabetes are also advised to have the annual flu vaccine. Our flu guide explains why.
When to get urgent help
Possible new type 1 diabetes: the four Ts
Toilet (passing much more urine), Thirsty, Tired, and Thinner, developing over days to weeks, need a same day assessment, particularly in a child or young adult. Do not wait for a routine appointment.
Call 999 or go to A&E if someone with these symptoms, or with known diabetes, also has:
- Vomiting or tummy pain
- Fast or deep breathing
- Breath that smells fruity, like pear drops or nail varnish remover
- Drowsiness or confusion
These can be signs of diabetic ketoacidosis, which is a medical emergency.
Low blood sugar (hypoglycaemia)
If you take insulin or a sulfonylurea, your blood sugar can drop too low, causing shakiness, sweating, hunger, palpitations, irritability, or confusion. Treat it straight away with 15 to 20g of fast acting sugar, such as glucose tablets, a small glass of fruit juice, or a few jelly sweets, then recheck after 10 to 15 minutes and follow with a starchy snack. Call 999 if someone is unconscious or cannot swallow safely.
Common questions
Short answers to the questions we are asked most often.
What is the difference between type 1 and type 2 diabetes?
Type 1 diabetes is an autoimmune condition in which the body stops making insulin. It comes on quickly, is not caused by lifestyle, and always needs insulin. Type 2 diabetes develops gradually as the body becomes resistant to insulin, and accounts for around 90% of cases.
What HbA1c level means diabetes?
An HbA1c of 48 mmol/mol (6.5%) or above indicates diabetes. A result of 42 to 47 mmol/mol (6.0 to 6.4%) is prediabetes, and below 42 mmol/mol is normal. If you have no symptoms, the diagnosis is usually confirmed with a second test.
What are the early symptoms of diabetes?
Passing urine more often, especially at night, feeling very thirsty, tiredness, unexplained weight loss, recurrent thrush, blurred vision, and wounds that heal slowly. Type 2 diabetes often causes no symptoms at all for years and is found on a routine blood test.
Can type 2 diabetes be reversed?
For many people, yes. Remission means blood sugar returning to the non diabetic range without diabetes medication. In the DiRECT trial, a structured weight management programme achieved remission in 46% of participants at one year. It is most likely in the first few years after diagnosis.
What does prediabetes mean?
Prediabetes means your blood sugar is higher than normal but not yet in the diabetes range. It causes no symptoms and is not inevitable. Modest weight loss and regular activity cut the risk of progressing to type 2 diabetes by around half.
Next steps
If you have symptoms, a family history, or simply want to know where you stand, a blood test will give you a clear answer. If you already have diabetes or prediabetes and would like more time to go through your results and options, we are happy to help.