Diabetes is a lifelong condition that causes a person's blood sugar level to become too high.
There are two main types of diabetes – type 1 diabetes and type 2 diabetes.
In 2010, there were approximately 3.1 million people aged 16 or over with diabetes (both diagnosed and undiagnosed) in England.
By 2030, this figure is expected to rise to 4.6 million, with 90% of those affected having type 2 diabetes.
The charity Diabetes UK estimates that around 850,000 people in England have diabetes but haven't been diagnosed.
Many more people have blood sugar levels above the normal range, but not high enough to be diagnosed as having diabetes.
This is sometimes known as prediabetes. If your blood sugar level is above the normal range, your risk of developing full-blown diabetes is increased.
It's very important for diabetes to be diagnosed as early as possible because it will get progressively worse if left untreated.
You should therefore visit your GP as soon as possible if you have symptoms, such as feeling thirsty, passing urine more often than usual, and feeling tired all the time.
Symptoms of diabetes
The main symptoms of diabetes are:
feeling very thirsty
urinating more frequently than usual, particularly at night
feeling very tired
weight loss and loss of muscle bulk
itching around the penis or vagina, or frequent episodes of thrush
cuts or wounds that heal slowly
blurred vision (caused by the lens of the eye becoming dry)
Type 1 diabetes can develop quickly over weeks or even days.
Many people have type 2 diabetes for years without realising because the early symptoms tend to be general.
What causes diabetes?
The amount of sugar in the blood is controlled by a hormone called insulin, which is produced by the pancreas (a gland behind the stomach).
When food is digested and enters your bloodstream, insulin moves glucose out of the blood and into cells, where it's broken down to produce energy.
However, if you have diabetes, your body is unable to break down glucose into energy. This is because there's either not enough insulin to move the glucose, or the insulin produced doesn't work properly.
Type 1 diabetes
In type 1 diabetes, the body's immune system attacks and destroys the cells that produce insulin. As no insulin is produced, your glucose levels increase, which can seriously damage the body's organs.
Type 1 diabetes is often known as insulin-dependent diabetes. It's also sometimes known as juvenile diabetes or early-onset diabetes because it usually develops before the age of 40, often during the teenage years.
Type 1 diabetes is less common than type 2 diabetes. In the UK, it affects about 10% of all adults with diabetes.
If you're diagnosed with type 1 diabetes, you'll need insulin injections for the rest of your life.
You'll also need to pay close attention to certain aspects of your lifestyle and health to ensure your blood glucose levels stay balanced.
For example, you'll need to eat healthily, take regular exercise and carry out regular blood tests.
Type 2 diabetes
Type 2 diabetes is where the body doesn't produce enough insulin, or the body's cells don't react to insulin. This is known as insulin resistance.
Type 2 diabetes is far more common than type 1 diabetes. In the UK, around 90% of all adults with diabetes have type 2 diabetes.
If you're diagnosed with type 2 diabetes, you may be able to control your symptoms simply by eating a healthy diet, exercising regularly, and monitoring your blood glucose levels.
However, as type 2 diabetes is a progressive condition, you may eventually need medication, usually in the form of tablets.
Type 2 diabetes is often associated with obesity. Obesity-related diabetes is sometimes referred to as maturity-onset diabetes because it's more common in older people.
You can use the BMI healthy weight calculator to check whether you're a healthy weight.
Diabetic eye screening
Everyone with diabetes aged 12 or over should be invited to have their eyes screened once a year.
If you have diabetes, your eyes are at risk from diabetic retinopathy, a condition that can lead to sight loss if it's not treated.
Screening, which involves a half-hour check to examine the back of the eyes, is a way of detecting the condition early so it can be treated more effectively.
Gestational diabetes (in pregnancy)
During pregnancy, some women have such high levels of blood glucose that their body is unable to produce enough insulin to absorb it all. This is known as gestational diabetes and affects up to 18 in 100 women during pregnancy.
Pregnancy can also make existing type 1 diabetes worse. Gestational diabetes can increase the risk of health problems developing in an unborn baby, so it's important to keep your blood glucose levels under control.
In most cases, gestational diabetes develops during the second trimester of pregnancy (weeks 14 to 26) and disappears after the baby is born.
However, women who have gestational diabetes are at an increased risk (30%) of developing type 2 diabetes later in life (compared with a 10% risk for the general population).
Diabetic eye screening
Eye screening is a key part of your diabetes care. If you have diabetes, your eyes are at risk of damage from diabetic retinopathy, a condition that can lead to sight loss if it's not treated.
Diabetic retinopathy occurs when diabetes affects small blood vessels, damaging the part of the eye called the retina. When the blood vessels in the central area of the retina (the macula) are affected, it is known as diabetic maculopathy.
Diabetic retinopathy is one of the most common causes of sight loss among people of working age.
However, you may not know that you have diabetic retinopathy as it does not usually cause any noticeable symptoms in the early stages.
Screening is a way of detecting the condition early before you notice any changes to your vision.
If retinopathy is detected early enough, treatment can stop it getting worse. Otherwise, by the time symptoms become noticeable, it can be much more difficult to treat.
The check takes about half an hour and involves examining the back of the eyes and taking photographs of the retina.
Read on to find out when screening is offered, what happens at your screening appointment, and what you'll learn from your screening results.
When is diabetic eye screening offered?
Everyone with diabetes who is 12 years of age or over should be invited to have their eyes screened once a year.
You should receive a letter from your local Diabetic Eye Screening Service inviting you to attend a screening appointment. The letter will include a leaflet about diabetic eye screening.
Contact your local screening service or your GP if you have not received a letter and your appointment is overdue. You can look up your local screening service here – your service will be the one nearest to your GP surgery.
The invitation will say where you need to go. This may be your GP surgery, your local hospital, a local optician's practice, or another nearby clinic.
Bring all the glasses and contact lenses you wear, along with lens solution for contacts.
If you have sight problems in between screening appointments, such as sudden vision loss or a deterioration in your vision, seek immediate medical advice. Do not wait until your next screening appointment.
Diabetic eye screening in pregnancy
If you have diabetes and become pregnant, you will need special care as there are risks to both mother and baby associated with the condition.
You'll be offered additional tests for diabetic retinopathy at or soon after your first antenatal clinic visit, and also after 28 weeks of pregnancy.
If the early stages of retinopathy are found at the first screening, you will also be offered another test between 16 and 20 weeks of pregnancy.
If serious retinopathy is found at any screening, you will be referred to an eye specialist.
Some women who do not have diabetes can develop hyperglycaemia (high blood sugar) during pregnancy. This is known as gestational diabetes.
Pregnant women who develop gestational diabetes are not offered screening for diabetic retinopathy.
Other eye checks
Diabetic eye screening is not covered as part of your normal eye examination with an optician.
Screening does not look for other eye conditions, so you should continue to visit your optician regularly for an eye examination as well.
What happens during diabetic eye screening?
The screening appointment should last about 30 minutes.
When you arrive, the procedure will be explained to you. If you have any questions, ask the healthcare professional who is treating you.
You will be given eye drops to enlarge your pupils, which takes between 15 and 20 minutes, and photographs of your retina will be taken.
There will be a flash of light each time a photograph is taken, but the camera will not touch your eye. Although the light is bright, it should not be uncomfortable.
The eye drops may cause your eyes to sting slightly, and after about 15 minutes your vision will be blurred. You may find it difficult to focus on objects that are close to you.
Depending on the type of eye drops used, the blurring can last between two and six hours. You won't be able to drive home from your appointment, so you may want to bring someone with you.
After the screening procedure, you may also find that everything looks very bright. You may want to take a pair of sunglasses to wear afterwards.
In very rare cases, the eye drops can cause a sudden pressure increase within the eye.
This will require prompt treatment at an eye unit. The symptoms of a pressure increase are:
pain or severe discomfort in your eye
redness of the white of your eye
constantly blurred vision, sometimes with rainbow halos around lights
If you experience any of these symptoms after screening, go back to the screening centre or your nearest accident and emergency (A&E) department.
Your screening results
Within six weeks, both you and your GP should receive a letter letting you know your results.
You will not get the results immediately as the photographs will need to be studied by a number of different healthcare professionals, including someone who is trained in identifying and grading retinopathy.
The screening results may show either:
background retinopathy – also called stage one retinopathy
degrees of referable retinopathy – this means retinopathy that requires referral to an eye specialist for further assessment and treatment
You may need to have a further assessment if:
the photographs are not clear enough to give an accurate result
you have retinopathy that could affect your sight and follow-up treatment is needed
you have retinopathy that needs to be checked more than once a year
other eye conditions are detected, such as glaucoma (a group of eye conditions that affect vision) or cataracts (cloudy patches in the lens of the eye)
If your results show no retinopathy or background retinopathy, you will be invited back for another screening appointment a year later.
You can also reduce your risk of developing diabetic retinopathy in the future by controlling your blood sugar levels and blood pressure.
If screening detects signs that diabetic retinopathy or maculopathy is threatening your sight, you will be given information about how far the condition has progressed. This will determine the type of treatment you receive.
If you have questions about your results, contact your local diabetic eye screening service. Their details should be on the letter you received from them. Alternatively, you can find your local screening service here.
For more information on diabetic eye screening, see our diabetic eye screening FAQs.