Type 1 diabetes

Expert review by:
  • Paul McArdle, Registered Dietitian
Content review by:
  • Liz Wolf, Freelance Health Editor

Type 1 diabetes means your body can't control the amount of glucose (sugar) in your blood. Your pancreas can’t make a hormone called insulin. This means that your blood glucose (blood sugar) level becomes too high. It’s a condition that you have for life.

About type 1 diabetes

There are two main types of diabetes: type 1 and type 2. Type 1 diabetes usually starts in childhood. It’s most often diagnosed between the ages of ten and 14. But you can develop it as an adult too. In the UK, around one in 12 people diagnosed with diabetes has type 1.

When you have type 1 diabetes, your body can’t produce insulin. This hormone usually controls the amount of glucose (sugar) in your blood. When you need energy, insulin helps glucose move from your blood into body tissues. Without insulin, glucose stays in the bloodstream and your blood glucose level becomes too high.

Causes of type 1 diabetes

Type 1 diabetes is an autoimmune condition. That means it’s caused by your body’s immune system which attacks and destroys the cells in your pancreas that make insulin.

There seem to be genetic factors involved in developing type 1 diabetes. You’re more likely to develop it if it runs in your family. But not everyone in these families develops diabetes, so there may be environmental factors that act as a trigger.

Symptoms of type 1 diabetes

If you have type 1 diabetes, you may:

  • need to pee more than usual
  • feel constantly thirsty
  • lose weight
  • feel extremely tired and weak
  • have blurred vision

Symptoms tend to start within days or weeks of type 1 diabetes developing. If not diagnosed, the high blood glucose (blood sugar) levels can lead to a complication called diabetic ketoacidosis. This causes other symptoms including:

  • feeling or being sick
  • tummy (abdominal) pain
  • fast pulse
  • rapid breathing
  • extreme tiredness or drowsiness

If you notice these symptoms in yourself or your child, contact a doctor. If symptoms are getting worse, go to A&E (accident and emergency).

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Diagnosis of type 1 diabetes

Your GP will ask about your symptoms and examine you. To see if you need further tests, they may prick your finger and test your blood. They may also want to test a urine sample. If a GP suspects your child has diabetes, they will send you and your child to hospital on the same day, to see a specialist diabetes team.

To fully diagnose diabetes, you need to have blood taken from a vein and tested to measure the level of glucose (sugar) in your blood. A blood glucose level above 11mmol/litre means it’s likely that you have diabetes. At the hospital, they will be able to confirm the diagnosis and start treatment straight away.

Blood tests to diagnose diabetes are usually repeated, to confirm the diagnosis. You may have a ‘fasting glucose’ test. That’s a blood test done when you haven’t eaten for at least 8 hours, usually first thing in the morning. You may also have blood tests for particular antibodies and proteins that can be markers for type 1 diabetes.

Management of type 1 diabetes

You can’t cure type 1 diabetes. But you should be able to live a normal life, with regular insulin and other measures to control your blood glucose (blood sugar). So type 1 diabetes shouldn’t stop you from doing any of the activities you’d normally do.

You usually have a team of diabetes specialists managing your care. They’ll discuss your care plan with you and review it regularly. They’ll talk you through everything you need to know about living with diabetes and how to manage your condition.


Taking insulin is an essential part of managing type 1 diabetes. It helps to control your blood sugar and keep the level as close to normal as possible. Your doctor will start you on insulin as soon as possible after you’re diagnosed with type 1 diabetes. You’ll need to take it for the rest of your life.

There are short-acting and long-acting types of insulin. This makes a difference to how frequently you need to take it. You might have your insulin:

  • as regular injections
  • through a pump

It’s most common to have injections. It’s best to inject in areas where there is a layer of fat. This is usually your thighs, buttocks or tummy (abdomen). These days, rather than using a bottle of insulin and a syringe, you usually have a pen-type device that you refill with insulin cartridges. You are likely to need injections spaced throughout the day, such as before every meal.

Pumps deliver a regular amount of insulin through a small tube called a cannula that lies just under your skin. Your doctor may recommend a pump if:

  • you are a child under 12
  • injections aren’t controlling your blood sugar well enough

You can talk over the type of insulin you need and how you have it with your doctor or diabetes specialist nurse.


With type 1 diabetes, there are no restrictions on what you can or can’t eat. But you should aim to follow a healthy, balanced diet. It should include healthy carbohydrates, fruit and vegetables with each meal. This will help to control your blood glucose level. Healthy carbohydrates are found in:

  • wholemeal bread, brown pasta and brown rice
  • other whole grains, such as bulgur wheat or quinoa
  • beans and lentils
  • fruits and vegetables

You’ll have to plan your insulin treatment quite closely around what you eat and how active you are. Everyone should be able to see a dietitian who specialises in diabetes. Adults diagnosed with diabetes should be offered structured education classes such as the DAFNE (dose adjustment for normal eating) programme to help with this.

Your dietitian might talk to you about ‘carb counting’. This means matching the amount of insulin you take to the amount of carbohydrate you’re eating. It can help you to be more flexible with your mealtimes and what you eat, depending on the type of insulin you’re on.

Monitoring your blood glucose level

A key part of managing your diabetes is checking your blood sugar regularly. The two main ways of doing this are:

  • pricking your fingertip, and using a blood glucose testing strip
  • wearing an electronic sensor that continuously measures your blood sugar (a continuous glucose monitor), or gives you a reading when you scan it (a flash monitor)

Your doctor will offer you a continuous glucose monitor (CGM) or a flash monitor. The difference between these is that you have to actively scan the flash monitor with a scanner or your smart phone. CGMs measure glucose levels every 1 to 5 minutes, automatically.

CGM and flash monitors have a tiny filament in the centre. You put them on with an applicator and a pin pushes the filament just underneath your skin. One sensor can stay on for up to two weeks.

You still have to do finger pricks if you have a sensor, but less often. You check the accuracy of the sensor against a finger prick test from time to time. If you don’t want to wear a sensor, you can do finger pricks throughout the day instead.

Whichever method you use, you’ll need to check your blood sugar:

  • first thing in the morning
  • before meals
  • before bed
  • if you’re ill
  • when exercising
  • before driving
  • if you have hypoglycaemic symptoms

Blood tests at the doctors (HbA1c)

Your GP will also monitor how well you’re controlling your blood glucose level. They do this with a regular HbA1c blood test, usually every 3 to 6 months. This measures how much glucose there is in your red blood cells. It can show how well you’ve been controlling your diabetes over the previous two or three months.

You’ll have a ‘target’ HbA1c to aim for. Trying to stick to this is really important in preventing long-term complications from diabetes.

Adjusting your insulin

As you get used to managing your diabetes, you’ll learn how to adjust your insulin dose to maintain a healthy blood glucose level. You’ll have to take your diet and physical activity into account, and make extra adjustments if you’re ill.

Some insulin pumps can be connected to a CGM to work out and deliver the amount of insulin you need automatically. These are usually only available privately. Even with a pump with CGM, you’ll have to make adjustments for meals.

Complications of type 1 diabetes

Diabetes can have complications if your blood glucose (blood sugar) level becomes either too high (hyperglycaemia), or too low (hypoglycaemia).


Your blood sugar can become too high if you:

  • become unwell
  • feel stressed
  • miss an insulin dose
  • don’t match the amount of carbohydrate you eat with your insulin dose

You may find that you’re thirstier than usual, need to pee more often and feel tired.

Without enough insulin, chemicals called ketones build up in your blood. This can make you feel extremely tired, feel sick or vomit. Some people notice their breath has a distinctive fruity smell, like pear drops. You’ll have a ketone monitor for testing your blood. Your doctor will tell you when to check your ketone level, and what to do if it’s too high.

Very high levels of ketones are dangerous. You can develop a condition called diabetic ketoacidosis (DKA). This is a medical emergency. You can become severely dehydrated and go into shock. If you think you may be at risk of DKA, get medical help straight away.

Long-term hyperglycaemia

Over time, if your blood sugar is frequently too high, it can damage body tissues and cause long-term complications. You will be at risk of:

  • kidney disease
  • nerve damage, causing tingling, burning or numbness
  • foot problems, including infections, ulcers and problems related to lack of blood flow
  • damage to your eyes, leading to blindness
  • heart disease and stroke
  • infections that are frequent or don’t go away, especially urinary infections

Many of these problems are caused by the high glucose levels damaging the smallest blood vessels, such as those in the kidneys, eyes and heart.

If you have numbness in your feet, you may not notice small injuries, which can then get worse and develop into ulcers.


This means your blood sugar level is too low, usually below 4mmol/litre. It’s often called a ‘hypo’. It can happen if you take too much insulin, skip or delay a meal or misjudge the amount of carbohydrate you need. It can also happen if you’re more active than usual or if you drink alcohol.

Most people get warning signs when their glucose level begins to fall. These include:

  • feeling hungry
  • sweating a lot
  • feeling your heart pounding
  • being anxious or irritable
  • feeling shaky
  • tingling lips

If your blood glucose level continues to fall, you may start feeling dizzy, confused, weak and lethargic. You may also have blurred vision.

Hypoglycaemia can be dangerous if not dealt with quickly. As soon as you notice symptoms, you need to eat or drink 15 to 20g of a fast-acting carbohydrate straight away. That’s about five or six glucose tablets, one or two tubes of glucose gel, or up to 180ml of a full-sugar fizzy drink.

Check your blood glucose after 10 to 15 minutes and if it hasn’t returned to normal, have something more to drink or take more glucose tablets. Once your blood glucose starts to get back to normal, you may need to eat something containing longer-lasting carbohydrates such as a sandwich or some cereal.

If you have a hypo and lose consciousness, you should have a prepared injection of a medicine called glucagon. Your healthcare team will show family members or a friend how to give it to you in case of emergency. Make sure family and friends know that they’ll need to call for emergency help immediately if you don’t have glucagon, or your blood glucose level doesn’t return to normal after taking it. After a severe hypo, you will need to have a review with your specialist diabetes team.

It’s a good idea to wear a medical emergency identification bracelet or similar, so that people know you have diabetes and take insulin.

Living with type 1 diabetes

Following a healthy lifestyle can help to control your blood glucose (blood sugar) and reduce your risk of complications.

What you eat is important for your general health. However, it will only help to control your blood sugar if you match the carbohydrate you eat to your insulin dose.

A healthy, balanced diet means low in fat, sugar and salt, and with at least five portions of fruit or vegetable every day. This will help you to keep to a healthy weight and prevent cardiovascular disease.

If you smoke, try to stop. Smoking is particularly bad if you have diabetes. It increases your risk of circulatory problems, heart disease and stroke, which is already raised because of your diabetes.


Keeping active can help to lower your blood glucose level and lower your risk of diabetes complications, including heart disease and stroke. It can also help you to stay a healthy weight. Even if you don’t do any sports, you can get exercise from daily activities such as housework or gardening.

Being more active will increase your body’s need for energy. You may need to eat before or after exercising and may need to adjust your insulin. Check your blood sugar before and after taking any exercise.


If you have diabetes, alcohol on an empty stomach can increase your risk of a hypo. Alcohol can also make the signs of a hypo less clear. Check your blood glucose regularly if you’re drinking. Otherwise, general health advice applies: have no more than 14 units a week, spread over several days.


You’re obliged to tell the Driver and Vehicle Licensing Agency (DVLA) when you’re diagnosed with type 1 diabetes. By law, you must check your blood sugar no more than 2 hours before starting any journey. Check again every 2 hours during a journey. If it’s less than 5mm/l, you can’t drive. Have a snack, wait 45 minutes and check again. Keep glucose tablets, gel or a fizzy drink in the car in case your blood sugar starts to dip.

If you develop any sight problems or have a severe hypo, you must tell the DVLA. There are stricter rules for commercial driving, so check the DVLA website for more information.

To diagnose diabetes, you need to have a blood test. This is usually repeated to make sure as blood glucose (sugar) levels can vary. See our section on diagnosing diabetes for more information.

Type 1 diabetes is usually diagnosed in children, but it can sometimes be diagnosed in adulthood. See the section: About diabetes.

Early signs usually include feeling very thirsty, peeing a lot and losing weight. You may also feel very tired. See our symptoms section for more information.

Your body can’t get energy to your body’s cells if you have diabetes. This means that if type 1 diabetes is untreated, it will be fatal. But if you manage it well, there’s no reason why you can’t live a perfectly normal life. See our section on managing diabetes for detailed information.

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  • Type 1 diabetes. BMJ Best Practice., last reviewed February 2023
  • Type 1 diabetes. Diabetes UK., accessed March 2023
  • Types of diabetes. Diabetes UK., accessed March 2023
  • Family health history and diabetes. Centers for Disease Control and Prevention (CDC)., last reviewed May 2022
  • Oxford Handbook of Endocrinology and Diabetes. 4th ed. Oxford Academic., published November 2021
  • Diabetes tests & diagnosis. National Institute of Diabetes and Digestive and Kidney Diseases., last reviewed July 2022
  • Diabetes (type 1 and type 2) in children and young people: diagnosis and management. National Institute for Health and Care Excellence (NICE)., last updated June 2022
  • Diabetes - type 1. NICE Clinical Knowledge Summaries., last revised January 2023
  • Scenario: Management of children and young people with diabetes. NICE Clinical Knowledge Summaries., last revised January 2023
  • Scenario: Management of adults with type 1 diabetes. NICE Clinical Knowledge Summaries., last revised January 2023
  • Diabetes treatments. Diabetes UK., accessed March 2023
  • Insulin therapy in type 1 diabetes. NICE Clinical Knowledge Summaries., last revised July 2020
  • Injecting insulin. Diabetes UK., accessed March 2023
  • Insulin pumps. Diabetes UK., accessed March 2023
  • I have type 1 diabetes - what can I eat? Diabetes UK., accessed March 2023
  • Carbohydrates. Harvard T.H. Chan School of Public Health., accessed March 2020
  • Checking your blood sugar levels. Diabetes UK., accessed March 2023
  • Flash glucose monitors (Freestyle Libre) and continuous glucose monitors (CGM). Diabetes UK., accessed March 2023
  • What is HbA1c? Diabetes UK., accessed March 2023
  • Diabetes and intercurent illness. Patient., last reviewed March 2023
  • Hyperglycaemia (Hyper). Diabetes UK., accessed March 2023
  • What is DKA (Diabetic ketoacidosis)? Diabetes UK., accessed March 2023
  • Ketones and diabetes. Diabetes UK., accessed March 2023
  • Management of type 1 diabetes. Patient., last reviewed August 2021
  • Urinary tract infections - UTIs., last reviewed January 2023
  • Complications of diabetes mellitus. MSD Manuals., last updated September 2022
  • What is a hypo? Diabetes UK., accessed March 2023
  • Having a hypo. Diabetes UK., accessed March 2023
  • Healthy living. Diabetes Research and Wellness Foundation., accessed March 2023
  • Diabetes and exercise. Diabetes UK., accessed March 2023
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