Diabetes is a lifelong condition that causes a person's blood sugar (glucose) level to become too high.
The hormone insulin – produced by the pancreas – is responsible for controlling the amount of glucose in the blood.
There are two main types of diabetes:
Type 1 – where the pancreas doesn't produce any insulin
Type 2 – where the pancreas doesn't produce enough insulin or the body’s cells don't react to insulin
Another type of diabetes, known as gestational diabetes, occurs in some pregnant women and tends to disappear following birth.
It's very important for diabetes to be diagnosed as soon as possible, because it will get progressively worse if left untreated.
You should therefore visit your GP if you have symptoms, which include feeling thirsty, passing urine more often than usual and feeling tired all the time (see the list below for more diabetes symptoms).
Type 1 and type 2 diabetes
Type 1 diabetes can develop at any age, but usually appears before the age of 40, particularly in childhood. Around 10% of all diabetes is type 1, but it's the most common type of childhood diabetes. This is why it's sometimes called juvenile diabetes or early-onset diabetes.
In type 1 diabetes, the pancreas (a small gland behind the stomach) doesn't produce any insulin – the hormone that regulates blood glucose levels. This is why it's also sometimes called insulin-dependent diabetes.
If the amount of glucose in the blood is too high, it can, over time, seriously damage the body's organs.
In type 2 diabetes, the body either doesn't produce enough insulin to function properly, or the body's cells don't react to insulin. Around 90% of adults with diabetes have type 2, and it tends to develop later in life than type 1.
The symptoms of diabetes occur because the lack of insulin means that glucose stays in the blood and isn’t used as fuel for energy.
Your body tries to reduce blood glucose levels by getting rid of the excess glucose in your urine.
Typical symptoms include:
feeling very thirsty
passing urine more often than usual, particularly at night
feeling very tired
weight loss and loss of muscle bulk
The symptoms of type 1 diabetes usually develop very quickly in young people (over a few days or weeks). In adults, the symptoms often take longer to develop (a few months).
Causes of type 1 diabetes
Type 1 diabetes occurs as a result of the body being unable to produce insulin, which moves glucose out of the blood and into your cells to be used for energy.
Without insulin, your body will break down its own fat and muscle, resulting in weight loss. This can lead to a serious short-term condition called diabetic ketoacidosis, where the bloodstream becomes acidic and you develop dangerous levels of dehydration.
Type 1 diabetes is an autoimmune condition, where the immune system (the body's natural defence against infection and illness) mistakes the cells in your pancreas as harmful and attacks them.
Treating type 1 diabetes
It's important that diabetes is diagnosed as early as possible, so that treatment can be started.
Diabetes can't be cured, but treatment aims to keep your blood glucose levels as normal as possible and control your symptoms, to prevent health problems developing later in life.
If you're diagnosed with diabetes, you'll be referred to a diabetes care team for specialist treatment and monitoring.
As your body can't produce insulin, you'll need regular insulin injections to keep your glucose levels normal. You'll be taught how to do this and how to match the insulin you inject to the food you eat, taking into account your blood glucose level and how much exercise you do.
Insulin injections come in several different forms, with each working slightly differently. Some last up to a whole day (long-acting), some last up to eight hours (short-acting) and some work quickly but don't last very long (rapid-acting). You'll most likely need a combination of different insulin preparations.
There are alternatives to insulin injections, but they're only suitable for a small number of patients. They are:
insulin pump therapy – where a small device constantly pumps insulin (at a rate you control) into your bloodstream through a needle that's inserted under the skin
islet cell transplantation – where healthy insulin-producing cells from the pancreas of a deceased donor are implanted into the pancreas of someone with type 1 diabetes (read about the criteria for having an islet transplant)
a complete pancreas transplant
If diabetes is left untreated, it can cause a number of different health problems. Large amounts of glucose can damage blood vessels, nerves and organs.
Even a mildly raised glucose level that doesn't cause any symptoms can have damaging effects in the long term.
Living with diabetes
If you have type 1 diabetes, you'll need to look after your health very carefully. Caring for your health will also make treating your diabetes easier and minimise your risk of developing complications.
For example, eating a healthy, balanced diet and exercising regularlywill lower your blood glucose level. Stopping smoking (if you smoke) will also reduce your risk of developing cardiovascular disease.
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. Everyone with diabetes aged 12 or over should be invited to have their eyes screenedonce a year.
Symptoms of type 1 diabetes
The symptoms of type 1 diabetes can develop very quickly (over a few days or weeks), particularly in children.
In older adults, the symptoms can often take longer to develop (a few months).
However, they should disappear when you start taking insulin and you get the condition under control.
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
itchiness around the genital area, or regular bouts of thrush (a yeast infection)
blurred vision caused by the lens of your eye changing shape
slow healing of cuts and grazes
Vomiting or heavy, deep breathing can also occur at a later stage. This is a dangerous sign and requires immediate admission to hospital for treatment.
You should visit your GP immediately if you think you may have diabetes.
When to seek urgent medical attention
You should seek urgent medical attention if you have diabetes and develop:
a loss of appetite
nausea or vomiting
a high temperature
fruity smelling breath – which may smell like pear drops or nail varnish (others will usually be able to smell it, but you won't)
Hypoglycaemia (low blood glucose)
If you have diabetes, your blood glucose levels can become very low. This is known as hypoglycaemia (or a "hypo"), and it's triggered when injected insulin in your body moves too much glucose out of your bloodstream.
In most cases, hypoglycaemia occurs as a result of taking too much insulin, although it can also develop if you skip a meal, exercise very vigorously or drink alcohol on an empty stomach.
Symptoms of a "hypo" include:
feeling shaky and irritable
nausea (feeling sick)
A hypo can be brought under control simply by eating or drinking something sugary.
If it isn't brought under control, a hypo can cause confusion, slurred speech and, eventually, unconsciousness.
In this case, an emergency injection of a hormone called glucagon will be needed. Glucagon increases the glucose in your blood.
Hyperglycaemia (high blood glucose)
As diabetes occurs as a result of your body being unable to produce any, or enough, insulin to regulate your blood glucose, your blood glucose levels may become very high. This happens because there's insufficient insulin to move glucose out of your bloodstream and into your cells to produce energy.
If your blood glucose levels become too high, you may experience hyperglycaemia. The symptoms of hyperglycaemia are similar to the main symptoms of diabetes, but they may come on suddenly and be more severe. They include:
a dry mouth
a need to pass urine frequently
Left untreated, hyperglycaemia can lead to diabetic ketoacidosis. This is a serious condition, where the body breaks down fat and muscle as an alternative source of energy. This leads to a build-up of acids in your blood, which can cause vomiting, dehydration, unconsciousness and even death.
Causes of type 1 diabetes
Type 1 diabetes occurs when the body is unable to produce insulin. Insulin is a hormone that's needed to control the amount of sugar (glucose) in your blood.
When you eat, your digestive system breaks down food and passes its nutrients – including glucose – into your bloodstream.
The pancreas (a small gland behind your stomach) usually produces insulin, which transfers any glucose out of your blood and into your cells, where it's converted to energy.
However, if you have type 1 diabetes, your pancreas is unable to produce any insulin (see below). This means that glucose can't be moved out of your bloodstream and into your cells.
Type 1 diabetes is an autoimmune condition. Your immune system (the body's natural defence against infection and illness) mistakes the cells in your pancreas as harmful and attacks them, destroying them completely or damaging them enough to stop them producing insulin.
It's not known exactly what triggers the immune system to do this, but some researchers have suggested that it may be due to a viral infection.
Type 1 diabetes is often inherited (runs in families), so the autoimmune reaction may also be genetic.
If you have a close relative – such as a parent, brother or sister – with type 1 diabetes, you have about a 6% chance of also developing the condition. The risk for people who don't have a close relative with type 1 diabetes is just under 0.5%.
Diagnosing type 1 diabetes
It's important to diagnose diabetes as early as possible, so that treatment can be started.
If you experience the symptoms of diabetes, you should visit your GP as soon as possible. They'll ask about your symptoms and may request a urine and blood test.
Urine and blood tests
Your urine sample will be tested to see whether it contains glucose. Urine doesn't usually contain glucose, but if you have diabetes, some glucose can overflow through the kidneys and into the urine. Your urine may also be tested for ketones (chemicals) that indicate type 1 diabetes.
If your urine contains glucose, a blood test can be used to confirm the diagnosis of diabetes. A sample of your blood will be taken in the morning, before you've had anything to eat, and it will be tested to measure your blood glucose levels.
If your blood glucose levels aren't high enough for your GP to diagnose diabetes, you may need to have an oral glucose tolerance test (OGTT), which is also sometimes referred to as a glucose tolerance test (GTT).
After drinking a glucose drink, samples of your blood will be taken every half an hour, for two hours. The samples will be tested to find out how your body is dealing with the glucose.
Glycated haemoglobin (HbA1c)
The glycated haemoglobin (HbA1c) test is another blood test that can be used to diagnose diabetes.
In people who've already been diagnosed with diabetes, the HbA1c test is often used to show how well their diabetes is being controlled.
The HbA1c test gives your average blood glucose level over the previous two to three months. The results can indicate whether the measures you're taking to control your diabetes are working.
There are blood tests for specific antibodies that can identify type 1 diabetes.
If you've been diagnosed with diabetes, it's recommended that you have your HbA1c measured at least twice a year. However, you may need to have your HbA1c measured more frequently if:
you've recently been diagnosed with diabetes
your blood glucose remains too high
your treatment plan has been changed
Unlike other tests, such as the GTT, the HbA1c test can be carried out at any time of day and doesn't require any special preparation, such as fasting. However, it's less reliable in certain situations, such as during pregnancy.
The advantages associated with the HbA1c test make it the preferred method of assessing how well blood glucose levels are being controlled in a person with diabetes.
HbA1c is also increasingly being used as a diagnostic test for type 2 diabetes, and as a screening test for people at high risk of diabetes.
Treating type 1 diabetes
There's no cure for diabetes, so treatment aims to keep your blood glucose levels as normal as possible and to control your symptoms to prevent health problems developing later in life.
If you've been diagnosed with diabetes, you'll be referred for specialist treatment from a diabetes care team. They'll be able to explain your condition in detail and help you understand your treatment. They'll also closely monitor your condition to identify any health problems that may occur.
Type 1 diabetes occurs because your body can't produce enough insulin. This means you'll need regular insulin treatment to keep your glucose levels normal.
Insulin comes in several different preparations, each of which works slightly differently. For example, some last up to a whole day (long-acting), some last up to eight hours (short-acting) and some work quickly but don't last very long (rapid-acting). Your treatment is likely to include a combination of these different insulin preparations.
If you have type 1 diabetes, you'll probably need insulin injections. Insulin must be injected, because if it were taken as a tablet, it would be broken down in your stomach – like food – and would be unable to enter your bloodstream.
When you're first diagnosed, your diabetes care team will help you with your insulin injections, before showing you how and when to do it yourself. They'll also show you how to store your insulin and dispose of your needles properly.
Insulin injections are usually given by an injection pen, which is also known as an insulin pen or auto-injector. However, injections are sometimes given using a syringe. Most people need two to four injections a day.
Your GP or diabetes nurse may also teach one of your close friends or relatives how to inject the insulin properly.
Insulin pump therapy
Insulin pump therapy is an alternative to injecting insulin. An insulin pump is a small device that holds insulin and is about the size of a pack of playing cards.
The pump is attached to you by a long, thin piece of tubing, with a needle at the end, which is inserted under your skin. Most people insert the needle into their stomach, but you could also insert it into your hips, thighs, buttocks or arms.
The pump allows insulin to continuously flow into your bloodstream at a rate you can control. This means you no longer need to give yourself injections, although you'll need to monitor your blood glucose levels very closely to ensure you're receiving the right amount of insulin.
Insulin pump therapy can be used by adults, teenagers and children (with adult supervision) who have type 1 diabetes. However, it may not be suitable for everyone. Your diabetes care team may suggest pump therapy if you have frequent episodes of low blood glucose (hypoglycaemia).