What is Diabetes?
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‘Diabetes” is a group of disorders characterised by a higher than normal blood glucose (sugar) level (hyperglycaemia). Blood glucose levels are normally controlled by the hormone insulin; this is produced by beta-cells in the pancreas (a gland which lies just below the stomach).
Glucose, from the sugars and starches that we eat, is transported in the bloodstream. Insulin is needed for glucose to leave the bloodstream and enter the body’s cells where it is burned to provide energy. Without insulin, cells are deprived of glucose and energy, and the blood glucose level rises.
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Which TYPE? The ‘Type’ of diabetes depends on the underlying cause of the high blood glucose level: 9 times out of 10 this is down to insulin not working properly and over a period of years less and less insulin is produced; this is Type 2 diabetes. Approximately 1 in 10 cases of diabetes occurs due to the destruction of the insulin-producing cells, usually down to the body’s immune system turning on itself. When this happens no insulin is produced; this is Type 1 diabetes. The third common form of diabetes occurs during pregnancy, and usually lasts only for the duration of the pregnancy, although many women will then go on to develop Type 2 diabetes later on in life. You can find a full breakdown of all the various Types of diabetes on the ‘Classification of Diabetes’ page. |
What’s covered on this page
Type 1 and Type 2 Diabetes
In Type 1 diabetes (T1DM), the cells that should produce insulin have been destroyed. At the moment, people with Type 1 diabetes face daily insulin injections or continuous infusion of insulin for the remainder of their lifetime.
In Type 2 diabetes (T2DM), which is far more common, the body doesn’t respond properly to insulin, and often not enough insulin is produced. People with Type 2 diabetes may require only a change in diet, combined with increased levels of activity to promote weight loss, but often tablets are prescribed as well. Many people with Type 2 diabetes eventually go on to need insulin injections.
A comparison of Type 1 and Type 2 diabetes |
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Type 1 |
Type 2 | |
Symptoms |
May include the following: frequent urination, thirst, weight loss, extreme fatigue, acetone breath, nausea and vomiting, blurred vision and itchiness in the genital area. Symptoms tend to develop more gradually in Type 2 and are usually less severe. | |
Cause |
In most cases, the body is prompted to turn against itself and destroys the beta cells which produce insulin. This is brought about by cells of the immune system which should only respond to foreign invaders, and is known as an ‘autoimmune response’. | Insulin is produced but the body does not respond properly to it. This is known as ‘insulin resistance’. Often insufficient insulin is produced to cope with the body’s requirements. |
Treatment |
Insulin injections and a diet regimen. | Diet and exercise regimen. Tablets are often also required. Often insulin injections are needed, later on in life. |
A word about the terminology:
Type 1 diabetes is often referred to as insulin-dependent (IDDM) or juvenile-onset diabetes. Type 2 diabetes is often referred to as non-insulin dependent (NIDDM) or maturity-onset diabetes. People with NIDDM may require insulin treatment later on, so this is confusing terminology. The use of ‘juvenile onset’ and ‘maturity’ or ‘adult onset’ has diminished as we have learned more of the biology of the two types of diabetes. Defining diabetes as ‘Type 1’ or ‘Type 2’ according to the cause, as opposed to ‘IDDM’ or ‘NIDDM’ according to the treatment, is the most acceptable classification.
Other Types of Diabetes
Gestational Diabetes (GDM)
Pregnant women often develop diabetes. During pregnancy large quantities of hormones are produced; these hormones may reduce insulin action in the mother’s body, causing insulin resistance (similar to Type 2 diabetes). Treatment for gestational diabetes consists of diet and, sometimes, insulin therapy. The diabetes usually disappears after the baby is born, but many women do then develop Type 2 diabetes later on in their lives.
LADA
Latent Autoimmune Diabetes in Adults. It is becoming evident that a proportion of adults may have a slowly evolving kind of Type 1 diabetes, which is characterised by the presence of autoantibodies. Some people diagnosed with Type 2 diabetes soon find themselves dependent on insulin; these people may actually have a slowly progressive form of Type 1 diabetes or LADA.
MODY
Maturity Onset Diabetes of the Young. This is a rarer form of diabetes – a non insulin dependent condition which is diagnosed in young people. There is usually a clear pattern of dominant inheritance in MODY patients and investigation of this genetically defined subgroup of Type 2 diabetes has so far revealed more than six different genetic causes.
MIDD
Maternally Inherited Diabetes and Deafness has been identified as another less common subtype of diabetes, which is genetically defined.
Other specific forms
Some other specific forms or causes of diabetes are given below:
- Drug or chemical induced (includes steroids, thyroid hormone and ‘adrenergic agonists’
- Pancreatitis and other disease of the pancreas
- Diabetes is associated with some other diseases or syndromes, including:
- Syndrome X
- Cushing’s Syndrome
- Hyperthyroidism
- Haemochromatosis
- Leprechaunism
- Cystic Fibrosis
- ‘Stiff man’ Syndrome
- Other genetic syndromes
Diabetes occurring in such circumstances is often referred to as ‘secondary diabetes‘. In many instances though, there may be an existing tendency towards diabetes anyway; drugs or diseases, a few of which are mentioned above, then effectively act as an environmental stimulus, ‘unmasking’ the diabetes.
Some forms of secondary diabetes result in a lack of insulin and are similar, in many respects, to Type 1 diabetes. Others are associated with insulin resistance and show parallels with what we describe as Type 2 diabetes.
For a formal classification of diabetes, see Classification of Diabetes.
Reference: American Diabetes Association Professional Practice Committee. 2. Diagnosis and classification of diabetes: Standards of Care in Diabetes—2024. Diabetes Care 2024;47(Suppl. 1):S20–S42
The Effects of High Blood Glucose Levels
When blood passes through the filtering system in the kidneys, glucose is normally retained; but when the blood glucose level rises too high, glucose ‘spills over’ into the urine. This makes the urine so concentrated that extra water is drawn out too. People with untreated diabetes therefore produce large volumes of urine, becoming dehydrated and very thirsty. Fungal infections (such as thrush) thrive in the moist sugary environment of the genital area and can prove to be a persistent problem in people with diabetes.
In the absence of insulin, the body’s cells are not able to take glucose from the bloodstream. Messages are sent to the liver to release glucose from its stores because the cells believe that the body is in starvation. The blood glucose level rises… In desperation, cells turn to fats as a fuel instead. Burning up fats yields chemicals known as ketones. If these are produced faster than they can be disposed of by the body, they build up in the bloodstream and become toxic. Ketones make the blood too acidic and messages are sent from the brain to the lungs to breathe faster. You can smell ketones on the breath – fruity, like pear drops. If left untreated then vomiting, drowsiness and eventually coma will result. This life-threatening state is called diabetic ketoacidosis or DKA. It is usually only a potential problem for people with Type 1 diabetes.
Prolonged severe high blood glucose levels in people with Type 2 diabetes may lead to a condition known as ‘hyperosmolar non-ketotic coma‘ (HONK). This is caused by extreme loss of fluid (dehydration) and the resulting chemical imbalance in the blood.
Over a period of years, high blood glucose levels can cause damage to numerous body tissues, including the eyes, nerves, kidneys and heart. These ‘complications’ are chiefly the result of damaged blood vessels.
Treatments for Diabetes
Treatments for diabetes depend on the individual person and the type of diabetes. The aim of treatment is to keep blood glucose levels as near normal as possible.
Treatment for controlling blood glucose levels may consist of one of the following approaches:
- Diet and Exercise (T2DM, GDM)
- Diet and Exercise and Tablets (T2DM)
- Diet and Exercise and Tablets and Insulin (T2DM)
- Diet and Exercise and Insulin (T1DM, T2DM, GDM)
Daily finger-prick blood glucose testing is necessary and this is a tool that can be used to make your treatment work for you.
However, none of these treatment approaches work on a prescriptive basis. Successful diabetes therapy involves your conscious input from one day to the next, for the rest of your life. For this reason, your diabetes treatment will need to be complemented by your diabetes management or ‘self-care’ skills.
The appropriate treatment, plus good day-to-day diabetes management should help you to achieve good diabetes control.
Here, we outline the basic principles behind the different treatment approaches. There is more detailed information on the different aspects of diabetes treatment in the “Diabetes Management” sections.
Type 1 Diabetes (T1DM)
If you have Type 1 diabetes then your body will not be producing any insulin. Insulin is necessary for survival, so the only option is to provide the body with insulin from an outside source. Because it is a protein hormone, if it is taken by mouth (e.g. as a tablet) it is destroyed by the digestive system before it has chance to be absorbed. Insulin is therefore injected into the layer of fat that lies just beneath the skin. Alternatively, insulin can be supplied continuously by a pump; it is fed into the body through a long thin tube with a needle or plastic cannula that is inserted under the skin.
The amount of insulin that is given must closely match the body’s requirements in order to keep the blood glucose level in the right range. Too much insulin causes it to fall too low (hypoglycaemia) and too little causes it to rise too high (hyperglycaemia). Both of these conditions are unpleasant and can be dangerous if they are not corrected.
So, insulin needs to be closely matched with food intake (amount and timing) and exercise levels. This continual juggling act forms the crux of diabetes management and is only made possible with regular testing of blood glucose levels during the day.
Type 2 Diabetes (T2DM)
If you have Type 2 diabetes, your treatment will depend on a number of factors, including:
- Your body weight
- Your current eating habits
- Your current level of physical activity
- The severity of your symptoms
- Your blood glucose levels
- How long you have had diabetes for
You may at first be advised to make changes in your lifestyle – lose some weight and increase your level of physical activity, for example. Weight loss and exercise can be very successful in getting blood glucose levels back down to the normal range. Although it can be very difficult to change habits of a lifetime, the threat of your health deteriorating further may signify that now is the time to stop and take stock of things.
In some people, the ‘diet and exercise’ approach is simply not enough to bring blood glucose levels into line and extra help is needed. Usually the next step is tablets – known as oral hypoglycaemics – that either help you to produce more insulin, or help your body to use the insulin more effectively. These tablets, however, are only effective if your body is able to produce some insulin. You may be prescribed more than one type of tablet. You should remember that diet, weight loss and exercise are still crucial to the diabetes management plan even when tablets are prescribed.
Some people with Type 2 diabetes need insulin injections. This might be temporary – if your body is under a lot of stress, you have an infection or you have been admitted to hospital for surgery, for example. However, in many cases, Type 2 diabetes is a progressive condition in which insulin production declines slowly over the years. Eventually, not enough insulin is produced and then there is no alternative but to start on injections. If this happens to you then you must remember that this is not a failing on your part – it is just the natural progression of things.
Regardless of the treatment approach, people with Type 2 diabetes should ideally test blood glucose levels on a day-to-day basis. It is only with this information that you can assess the effects of your daily activities on your blood glucose level.
Gestational Diabetes (GDM)
The aim of treatment in Gestational diabetes is to bring blood glucose levels into the normal range in order to prevent complications of the pregnancy.
Dietary therapy is usually the first line of treatment. Refined foods and simple sugars should be replaced with more complex carbohydrates and fat intake should be reduced. A moderate restriction in calorie intake and increased exercise are generally recommended in overweight women.
In some women, modifying the diet is not sufficient to bring blood glucose levels down. In such cases, insulin injections are required.
The effectiveness of your diabetes management will largely be down to the choices that you make on a daily basis. Diabetes Info NZ aims to provide you with the information and tools to enable you to make the right choices.
Page updated: Jan 2025
Explore this section Introducing Diabetes:
Newly Diagnosed | What is Diabetes? | Diabetes and Insulin | Classification of Diabetes | Diagnosis of Diabetes | Managing Diabetes