Also known as: Diabetes mellitus
Last Review Date: August 1, 2018


Diabetes mellitus is a common condition in which the level of glucose (sugar) in an individual's blood becomes too high because the body cannot use it properly. In 2014-15, 5.1% of the Australian population (1.2 million people) had some type of diabetes, an increase from 4.5% in 2011-12. Apart from diagnosed diabetic population, up to 500,000 people might suffer from silent, undiagnosed type 2 diabetes.

There are two common forms of diabetes. Type 1 diabetes is due to destruction of the insulin producing islets in the pancreas. Type 2 diabetes is due to the pancreatic islets failing after many years of increased insulin production because of resistance to the action of insulin in many tissues of the body, especially in muscle.

Insulin is a hormone, produced by the pancreas, which controls the movement of glucose into most of the body's cells and maintains blood glucose levels within a narrow concentration range. Most tissues in the body rely on glucose for energy production, and all but a few - such as the brain and nervous system - are entirely reliant on insulin to deliver this essential fuel.

Diabetes disrupts the normal balance between insulin and glucose. Usually after a meal, carbohydrate are broken down into glucose and other simple sugars. This causes blood glucose levels to rise and stimulates the pancreas to release insulin into the bloodstream. Insulin allows glucose into the cells, where it also promotes storage of excess glucose - either as glycogen in the liver or as triglycerides in adipose (fat) cells. If there is insufficient or ineffective insulin, glucose levels remain high in the bloodstream and the body's cells ‘starve’.

Diabetes can cause both short term and long-term problems depending on the severity of the imbalance. In the short term it can upset the body's electrolyte balance, causing dehydration as high blood glucose levels increase the amounts of urine passed. If unchecked, this can eventually lead to loss of consciousness, kidney failure and death. Over time, high glucose levels can damage blood vessels, nerves and organs throughout the body, contributing to other problems such as high blood pressureheart disease, kidney failure and loss of vision..

Types of diabetes

There are two main types of diabetes: Type 1 (which used to be called insulin dependent diabetes or juvenile diabetes) and Type 2 (which used to be known as non-insulin dependent diabetes or adult onset diabetes). In addition, gestational diabetes is a term used to describe diabetes which is recognised for the first time during pregnancy. Pancreatic disease or damage can also cause diabetes if the insulin producing beta cells are destroyed. There are uncommon genetically caused types as well.

Type 1 diabetes accounts for about  13 percent of cases of diabetes in the Australia (an estimated 158,900 people) which is 0.7% of Australian population. This is the most common cause in children. Most cases of type 1 diabetes are diagnosed in those under the age of 30. Symptoms often develop abruptly and the diagnosis is often made following an emergency admission to hospital. The patient may be seriously ill, even unconscious, with very high glucose levels and high levels of ketones (byproducts that result from the use of fat as an alternative energy source when glucose is unavailable). Type 1 diabetics make very little or no insulin. Any insulin producing beta cells patients have at the time of diagnosis are usually completely destroyed within 5 to 10 years leaving them entirely reliant on insulin injections.

The exact cause of type 1 diabetes is unknown, but a family history of diabetes, viruses that injure the pancreas, and autoimmune processes (where the body's own immune system destroys the beta cells) are all thought to play a role. Type 1 diabetics may have more severe medical complications than other forms of diabetes. For instance, currently 40% of those with type 1 diabetes develop serious kidney problems leading to kidney failure by the age of 50.

Type 2 diabetes The number of people with type 2 diabetes is growing. This accounts for 85% of all cases of diabetes in Australia.  It is estimated to be present in over 4% of the population. Within 20 years, the number of people in Australia with type 2 diabetes may increase from an estimated 870,000 in 2014, to more than 2.5 million. The most socially disadvantaged Australians are twice as likely to develop diabetes.

Type 2 diabetics do make their own insulin but it is not in a sufficient amount to meet their needs because their body has become resistant to its effects. At the time of diagnosis they may have typical symptoms of diabetes, especially thirst, weight loss or may be passing large amounts of urine, or they may not have any symptoms, and diagnosis may be made on finding high glucose concentrations in the blood. It generally occurs later in life, in those who are obese, sedentary and over 45 years of age.

Risk factors for developing type 2 diabetes include;

  • Weight excess / obesity
  • Central or abdominal obesity
  • Lack of exercise
  • Family history of diabetes
  • Smoking
  • Long (>8 to 9 hours/day) duration of sleep
  • Dietary patterns - consumption of red meat, processed meat, and sugar sweetened beverages
  • Medical conditions - gestational diabetes, cardiovascular disease, hyperuricemia, polycystic ovary syndrome, metabolic syndrome
Abnormal glucose metabolism can be documented years before the onset of overt diabetes. For example the Oral Glucose Tolerance Test (OGTT-see Table) may identify individuals whose ability to handle a high glucose meal is not normal but is not sufficiently abnormal to identify them as diabetic e.g.  Impaired fasting glucose or impaired glucose tolerance (sometimes referred to as ‘pre-diabetes) Table. Usually these individuals do not have any symptoms but if nothing is done to lower their glucose levels.  They are at great risk of developing diabetes. Recognising these conditions is important as recent evidence shows that progression to diabetes can be markedly reduced by simple measures such as a small amount of weight loss and exercise.

Gestational diabetes or GDM is defined as glucose intolerance that begins or is first diagnosed during pregnancy. Most women with gestational diabetes mellitus are normoglycemic after delivery. GDM generally develops and is diagnosed in the late second or early third trimester of the pregnancy. It may appear earlier, particularly in women with a high level of risk for GDM. GDM affects about 10 – 14% of pregnancies in Australia..

The prevalence is affected by maternal factors such as history of previous gestational diabetes, ethnicity, advanced maternal age, family history of diabetes, pre-pregnancy weight and high gestational weight gain. Mothers of different ethnicity born in areas with high diabetes prevalence such as Polynesia, Asia and the Middle East, are three times as likely to have GDM as mothers born in Australia. Among Aboriginal and Torres Strait Islander mothers, GDM is twice as common, and pre-gestational diabetes affecting pregnancy is three to four times as common as in non-Indigenous mothers.

In pregnancy, there is a natural increase in levels of hormones including cortisol, growth hormone, human placental lactogen, and progesterone and prolactin levels, causing two to three fold increases in insulin resistance. The action of these hormones is usually compensated by increased insulin release. In pregnant women with abnormal glucose tolerance or impaired β-cell reserve, the pancreas is unable to sufficiently increase insulin secretion in order to control blood glucose.

In Australia, gestational diabetes is usually diagnosed by an oral glucose tolerance test performed between the 24th and 28th week of pregnancy or earlier if the woman is at high risk. If gestational diabetes is not treated, the baby is likely to be larger than normal, be born with low glucose levels, and be born prematurely. Potential maternal complications during pregnancy and delivery include pre-eclampsia and higher rates of caesarean delivery, maternal birth injury, and postpartum haemorrhage. Gestational diabetes also raises the risk of eventually developing type 2 diabetes, for both the mother and the baby.

Signs and symptoms

The signs and symptoms of diabetes are related to high glucose levels (hyperglycaemia), temporarily low glucose levels (hypoglycaemia), and to complications associated with diabetes. The complications can be related to lipid (fat) production, to macrovascular (large blood vessel) or microvascular (small blood vessel) damage, to organ damage - for example kidney (diabetic nephropathy), nerve (diabetic neuropathy) and eye (diabetic retinopathy) and/or to the slower healing associated with diabetes. Type 1 diabetics are often diagnosed with acute severe symptoms that require hospitalisation. With early type 2 diabetes and gestational diabetes there may be no symptoms.

Symptoms of type 1 and type 2 diabetes with hyperglycaemia may include any of:

  • Increased thirst
  • Passing increasing amounts of urine
  • Increased appetite (with type 1 weight loss is also seen)
  • Tiredness
  • Feeling sick
  • Vomiting
  • Stomach pain (especially in children)
  • Blurred vision
  • Slow-healing infections
  • Numbness, tingling and pain in the feet
  • Erectile dysfunction in men
  • Absence of menstruation in women
  • Rapid breathing (acute)
  • Decreased consciousness, coma (acute)

Symptoms of impending hypoglycaemia:
Hypoglycaemia is dangerous and may cause death. Temporary hypoglycaemia in the diabetic may be caused by the accidental injection of too much insulin, not eating enough or waiting too long to eat, exercising strenuously, or by the swings in glucose levels seen in patients with diabetes which is difficult to control (often referred to as 'brittle diabetes').

Hypoglycaemia needs to be treated because if it is severe, it can rapidly progress to unconsciousness. True hypoglycaemia occurs when the blood sugar is below 2.5 mmol/L, though symptoms may develop earlier, especially if the blood sugar falls rapidly, and include:

  • Sensation of hunger
  • Headache
  • Anxiety
  • Sweating
  • Confusion
  • Trembling
  • Weakness
  • Double vision
  • Convulsions (severe)
  • Coma (severe)


Diabetes is diagnosed either by measurement of HbA1c or glucose in blood (or more correctly in plasma which is the fluid left behind when cells have been removed from blood) in accordance with the criteria of the Australian Diabetes Association and the World Health Organisation.

Diagnostic criteria; A diagnosis of diabetes is made if one or more of following values are elevated.

  • A random venous plasma glucose concentration ≥ 11.1 mmol/l or
  • A fasting plasma glucose concentration ≥ 7.0 mmol/l or
  • Two hour plasma glucose concentration ≥ 11.1 mmol/l in an oral glucose tolerance test (OGTT) or
  • An HbA1c of ≥ 48mmol/mol (6.5%)

A single elevated test result is adequate for diabetes diagnosis if the patient is symptomatic. However, in the absence of typical symptoms repeat testing on another day is required for confirmation. If the fasting or random glucose concentrations do not fall into the criteria given above then an OGTT should be performed. The OGTT involves a fasting glucose, followed by the patient drinking a standard amount of a glucose solution to ‘challenge’ their system, followed by another glucose test two hours later.

Table of reference intervals for OGTT    
Diagnosis Fasting 2 hour glucose
Normal <6.1 mmmol/L <7.8 mmol/L
Impaired glucose tolerance <7.0 mmol/L 7.8 - 11.0 mmol/L
Impaired fasting glycaemia 6.1 - 6.9 mmol/L <7.8 mmol/L
Diabetes mellitus in the prescence
of symptoms or repeated
diabetic glucose level
>7.0 mmol/L >11.1 mmol/L

The HbA1c test does not require any patient preparation and can be performed at any time of day.

All women not known to have DM or GDM should have a standard 75 g OGTT at 24–28 weeks gestation.
In pregnancy OGTT apart from fasting and 2 hour plasma glucose, an extra plasma  glucose at one hour is performed. The diagnostic glucose levels are lower in pregnant women.

The ADIPS 2014 and IADPSG criteria for the diagnosis of GDM; A diagnosis of GDM could be made on one or more of these values:
            Fasting >5.1 mmol/L
            1 hour > 10.0 mmol/L
            2 hour ≥  8.5 mmol/L
Previous ADIPS Guidelines (Hoffman 1998, ADIPS 1998) for the Testing and Diagnosis of Gestational Diabetes Mellitus in Australia are still in use among some clinicians:
             Fasting                                ≥ 5.5 mmol/L
             2 h glucose                         ≥ 8.0 mmol/L

Sometimes random urines are tested for glucose, protein and ketones during a routine clinical examination using a 'dipstick test'. If glucose and/or protein or ketones is present on the dipped indicator strip then further investigations are necessary. This screening tool is not sensitive enough for monitoring patients who have been diagnosed as diabetic.

Tests for diabetes monitoring
Several laboratory tests may be used to monitor diabetes on a regular basis.

Glucose: Diabetic patients can monitor their condition by measuring their own blood glucose (capillary) levels. Self-monitoring of blood glucose (targets 6–8 mmol/L for fasting and 6–10 mmol/L for two hour postprandial) Capillary blood glucose results are lower compared with venous plasma glucose results. 

Measurement of capillary blood glucose is recommended only for type 1 diabetes or people with type 2 diabetes who are on insulin injections or pregnancy complicated by pre-existing diabetes or gestational diabetes mellitus (GDM).

Home blood measurements are done by placing a drop of blood (obtained by pricking the finger with a small lancet device), onto a plastic glucose test strip and then inserting the strip into a small test meter, which provides a digital readout of the blood glucose. Glucose measurements can be taken several times a day at a frequency which depends on how well their blood glucose concentration is controlled.

Haemoglobin A1c (HbA1c) - (Target  ≤7% (≤53 mmol/mol)

Fructosamine-  evaluates average glucose levels over the past 2 to 3 weeks­­

1,5-anhydroglucitol, 1,5-AG (or GlycoMark test) - is a new test that detects high glucose levels in the past 1 to 2 weeks. 1,5-Anhydroglucitol (1,5-AG) is predominantly of dietary origin. After its absorption, it is excreted by the kidney. When the blood sugar is high, urinary reabsorption of 1,5-AG is impaired, urinary excretion increases, and blood concentrations decline; therefore, 1,5-AG is a short-term marker of hyperglycaemia after meals that are not shown by HbA1c and fructosamine tests. The only other way to get this information is by frequent fingerprick blood glucose testing. Decreased 1,5-AG may particularly reflect postprandial hyperglycaemia (high blood sugar after eating). 1,5-AG may be useful to assess glycaemic control in patients haemoglobinopathies.
To monitor kidney function: Creatinine, eGFR, creatinine clearance, UACR (urine albumin creatinine ratio), Cystatin C, BUN, CMP

To monitor lipids: Triglycerides, cholesterol, HDL cholesterol, LDL cholesterol, Lipd profile


While there is no way to prevent type 1 diabetes, the risk of having type 2 diabetes can be greatly decreased by: losing excess weight, exercising and by eating a healthy diet with limited fat intake. By identifying pre-diabetic conditions (see table under Tests) and making the necessary lifestyle changes to lower glucose levels to normal levels you may be able to prevent type 2 diabetes or delay its onset by several years. Normalising blood glucose can also minimise or prevent vascular and kidney damage.

There is currently no cure for diabetes (although there has been some success with transplants including islet (beta) cell transplantations as a way to restore insulin production). The goals of diabetes treatment are to keep glucose levels close to normal and to treat any progressive vascular disease or organ damage that arises.

Diabetic treatment at the time of diagnosis may be very different from that required afterwards. Type 1 diabetics may be diagnosed following a short term illness, have very high blood glucose levels, electrolytes out of balance and be in a state of diabetic ketoacidosis (where their body has tried to break down fats to use as an alternate fuel source, leading to the toxic build up of ketones in the blood) with some degree of kidney failure. They may have become unconscious and comatose. This is a serious condition requiring immediate hospitalisation and expert care to get the body back to its normal balance.

Type 2 diabetics may occasionally be sick in a similar way to that described for type 1 diabetics. This may occur if they have ignored initial symptoms, if they have neglected their regular treatment, or if they have a serious stress to their system such as a heart attack, stroke or an infection. Very high blood glucose levels and dehydration reinforce each other, leading to weakness, confusion, convulsions, and to hyperglycaemic hyperosmolar (highly concentrated blood) coma. This is also a serious condition requiring immediate admission to hospital.

Regular diabetic treatment involves daily glucose monitoring and control, eating a healthy planned diet and exercising regularly (to lower glucose levels in the blood, increase the body's sensitivity to insulin and to increase blood circulation). It is important to work closely with your doctor or diabetes nurse and have regular checks that can include monitoring tests such as UACR, haemoglobin A1c, lipids and tests of kidney function in addition to blood pressure, eye and foot tests.

Immediate attention is required for complications such as:

  • Wound infections, especially on the feet, are slow to heal and if not addressed quickly may eventually lead to an amputation. Aggressive and specialised measures are often necessary
  • Vision problems, diabetic retinopathy can lead to eye damage, a detached retina, and to blindness. Laser surgery may be necessary
  • Urinary tract infections which may be frequent and resistant to antibiotic treatment

Type 1 diabetics must self-check their glucose levels and inject themselves with insulin from once to several times a day. (Insulin is not available in an oral form, it breaks down in the stomach so it must be injected under the skin). For some, a similar amount of insulin is taken every day; others prefer a more flexible regime where the amount and type of insulin injected is adjusted to take into account what they are eating, the size of their meals, and the amount of activity they are getting. There are several types of insulin available, some are fast acting and short lived while others take longer to act but have a longer duration of action.

Most type 1 diabetics use a combination of insulins to meet their needs, and maintaining control can sometimes be a challenge. Stress, illnesses, and infections can alter the amount of insulin necessary, and some type 1 diabetics have ‘brittle’ control - where glucose levels make rapid swings during the day.

A number of type 1 diabetics have turned to wearing insulin pumps, programmable devices that are carried at the waist and provide small amounts of insulin (through a needle under the skin) throughout the day to more closely match normal insulin secretion.

As another complicating factor, type 1 diabetics may develop antibodies to insulin. Over time, their body begins to identify the injections as an ‘intruder’ and works to destroy the insulin, resulting in the necessity of higher doses of insulin or of switching to a different kind.

Type 1 diabetics may also ‘overshoot’, running into trouble with low glucose levels (hypoglycaemia or ‘hypos’) if they inject too much insulin, go extended periods of time without eating, or if their needs change unexpectedly. They must carry glucose with them in the form of tablets or sweets and be ready to take some at the first signs of hypoglycaemia (low blood sugar).

Carrying glucagon injections is also recommended for times when their hypoglycaemia is not responding to oral glucose or for someone else to give them if they have become unconscious. Glucagon is a hormone which counteracts the action of insulin and increases glucose concentrations. Acute conditions, such as diabetic ketoacidosis or renal failure, may require admission to hospital to resolve.

Type 2 diabetics:  According to RACGP clinical guidelines patients should be screened for diabetes risk every three years from 40 years of age using the Australian type 2 diabetes risk assessment tool.  Screening involves fasting blood glucose (or glycated haemoglobin [HbA1c].) Type 2 diabetics range from those who can control their glucose levels with diet and exercise, through those who require oral medicines, to those who need to take daily insulin injections. Many will move along through this range as their disease progresses.

Monitoring of type 2 diabetes treatment is done with the following tests

  • Self-monitoring of blood glucose (targets 6–8 mmol/L for fasting and 6–10 mmol/L for two hour postprandial)
  • HbA1c (Target  ≤7% (≤53 mmol/mol)

The oral medicines fall into three groups, those that:

  • stimulate the pancreas to produce more insulin
  • help make the body more sensitive to the insulin it is producing, and
  • slow the absorption of carbohydrates in the stomach (slowing down the increase in blood glucose after a meal).

Type 2 diabetics often take 2 or more of these medicines, and/or insulin injections - whatever it takes to achieve glucose control.

With gestational diabetes, the mother-to-be will need to eat a modified diet, get regular exercise and monitor glucose regularly. If more control is needed, she will be given insulin injections (at this time oral medications are not used). Usually diabetic symptoms will decrease after birth, although the woman remains at a higher risk of becoming a type 2 diabetic and she should be carefully monitored with any subsequent pregnancies. Soon after birth her baby will be monitored for signs of hypoglycaemia and for any breathing distress.

Related pages

On this site
Tests: Glucose, insulin, C-peptide, UACR, HbA1c, fructosaminecystatin C, creatinine clearance, HDL cholesterol, triglycerides, lipid profile, cholesterol, LDL cholesterol, diabetes-related autoantibodies

Conditions: Kidney diseases, pancreatic diseases, heart disease, heart attack, stroke, insulin resistance

Elsewhere on the web
Diabetes Australia
Healthdirect Australia: Diabetes
Diabetes in Australia - facts