Diabetes mellitus (commonly known as diabetes) is a group of diseases characterised by high blood sugar levels over a prolonged period of time. This page deals with type 2 diabetes. Other variations of diabetes include:
- Type 1 diabetes – usually diagnosed in childhood or adolescence.
- Gestational diabetes – where a mother cannot produce enough insulin during pregnancy.
Almost 7% of adult New Zealanders, or approximately 200,000 people, have type 2 diabetes. The condition is more common among Māori, Pacifica, and Asian people than in European New Zealanders.
Type 2 diabetes used to be known as adult-onset diabetes and most often occurs in adulthood. It is increasingly being diagnosed in children and adolescents, which may be related to an increasing prevalence of obesity.
Type 2 diabetes develops when the body becomes resistant to the effects of insulin and/or when the pancreas gland stops producing enough insulin.
Insulin is a hormone that promotes the uptake of glucose from the blood into cells so that it can be metabolised (broken down) and used by the body as an energy source.
The direct effect of insulin is to lower blood glucose levels. However, when there is insufficient insulin or the body’s cells no longer respond to the effects of insulin, glucose accumulates in the blood, leading to high blood glucose levels. High blood glucose levels over a prolonged period of time are associated with serious health complications.
It is not understood why some people develop type 2 diabetes and others do not but certain factors can increase a person’s risk of the developing the condition. These risk factors include:
- Being overweight
- Fat distribution primarily around the abdomen
- Family history (parent or sibling with type 2 diabetes)
- Age (risk increases with ageing, especially after age 45 years)
- Prediabetes (when a person’s blood glucose level is slightly higher than normal, but not high enough to be classified as diabetes)
- Gestational diabetes
- Polycystic ovarian syndrome.
Signs and symptoms
Classic symptoms of type 2 diabetes are:
- Frequent urination (peeing)
- Excessive thirst or excessive fluid intake
- Excessive eating or excessive hunger
- Weight loss.
Other symptoms include: blurred vison, tingling, numbness, or a ‘pins and needles’ feeling in the lower limbs, and yeast infections.
The signs and symptoms develop gradually. Many people with type 2 diabetes do not have symptoms and so their condition remains undiagnosed, in some cases for many years.
Early diagnosis and treatment is important to help to prevent diabetes-related complications. Diagnosis of type 2 diabetes is primarily based on blood tests, which include:
- Random blood glucose test: A blood sample is taken at a random time. A random blood glucose level of 11.1 mmol/L or higher suggests diabetes, especially in the presence of the classic symptoms of diabetes.
- Fasting blood glucose test: A blood sample is taken after an overnight fast. A fasting blood glucose level of 7 mmol/L or higher on two separate tests confirms a diagnosis of diabetes.
- Glycosylated haemoglobin (Hb1Ac) test: This blood test is a measure of a person’s average blood glucose level for the past 2–3 months. An HB1Ac level of 6.5% or higher on two separate tests indicates diabetes.
If diabetes is suspected a doctor may also check a person’s eyes, kidneys, and heart to make sure there has been no damage due to diabetes.
Type 2 diabetes can be easy to ignore in its earlier stages but over time high blood glucose levels can damage blood vessels in the body leading to serious health complications including:
- Heart and blood vessel disease (cardiovascular disease)
- Damage to the nerves (neuropathy)
- Kidney disease (nephropathy)
- Visual problems (retinopathy)
- Foot problems (‘diabetic foot’)
- Hearing impairment
- Skin infections
Controlling blood glucose levels so that they stay in their normal healthy range can help to prevent these complications from developing.
It may be possible to manage the condition by eating healthy foods, exercising, and maintaining a healthy bodyweight. If these lifestyle changes are not enough to help the body to control its blood glucose level, diabetes medications or insulin therapy may also be needed.
The aim of treatment is to maintain healthy blood glucose levels, (ie: 4.0–8.0 mmol/L) and to prevent diabetes-related complications.
A high-fibre low-fat diet based on fruits, vegetables, and whole grains is recommended. Foods and beverages containing refined sugars should be avoided. Alcohol contains a lot of sugar so intake should be reduced.
Exercise helps to lower blood glucose levels. Regular exercise also helps to maintain a healthy body weight and control high blood pressure and high blood cholesterol levels. This in turn helps to reduce the risk of related health conditions such heart attack and stroke.
Although some people can achieve and maintain a normal blood glucose level with diet and exercise alone, others need diabetes medications or insulin therapy as well. Examples of diabetes medications include:
- Metformin is usually the first medication prescribed for type 2 diabetes. It works, in part, by helping the body to use insulin more effectively. If metformin and lifestyles changes are insufficient to control blood glucose levels, other oral or injected medications can be added.
- Sulfonylureas help the pancreas to secrete more insulin. Examples include glipizide and glimepiride. Notable side effects include low blood glucose (hypoglycaemia) and weight gain.
- Thiazolidinediones, like metformin, make the body's tissues more responsive to insulin. They are associated with some serious adverse effects and are generally not a first-choice treatment. Pioglitazone (Actos) is an example.
- DPP-4 inhibitors modestly lower blood glucose levels. Examples are sitagliptin (Januvia) and saxagliptin (Onglyza). These agents do not cause weight gain.
- GLP-1 receptor agonists slow digestion and help to lower blood glucose levels, though not as much as sulfonylureas. Their use is often associated with some weight loss. Exenatide (Byetta) and liraglutide (Victoza) are examples.
- SGLT2 inhibitors work by preventing the kidneys from reabsorbing glucose into the blood. Instead, the glucose is excreted in the urine. Examples include canagliflozin (Invokana) and dapagliflozin (Farxiga). Adverse effects include urinary tract infections, increased urination and low blood pressure.
- Insulin therapy was previously used as a last resort but today is more likely to be prescribed sooner because of its benefits. Insulin must be injected, which involves using a fine needle and syringe or an insulin pen injector. There are many types of insulin, and they each work in a different way. Examples include Insulin lispro (Humalog), Insulin glargine (Lantus).
People with type 2 diabetes and who are overweight (body mass index [BMI] greater than 35) may be eligible for weight-loss surgery (bariatric surgery).
Blood glucose monitoring
Depending on a person’s treatment plan, their blood glucose levels may need to be checked and recorded periodically or, if being treated with insulin, multiple times a day. Many factors can affect blood glucose levels so careful monitoring is the only way to ensure that blood sugar levels remain within their normal range. Two blood glucose level problems requiring immediate attention are:
- High blood glucose (hyperglycaemia): Eating too much or not taking enough diabetes medication can result in a blood glucose level that is too high. Signs and symptoms of hyperglycaemia include: frequent urination, increased thirst, dry mouth, blurred vision, fatigue, and nausea. Hyperglycaemia requires adjustment of meal plans, medications, or both.
- Low blood glucose (hypoglycaemia): Blood glucose levels can drop for many reasons, eg: skipping a meal, taking too much diabetes medication, or exercising more than usual. Hypoglycaemia is most likely when taking insulin or diabetes medications that promote the secretion of insulin. Signs and symptoms of hypoglycaemia include: sweating, shakiness, weakness, hunger, dizziness, headache, blurred vision, slurred speech, drowsiness, confusion, and potentially seizures. Drinking or eating something sweet/sugary will correct a low blood glucose level.
Further information and support
For further information and support contact your doctor, practice nurse, or any of the following organizations.
Diabetes New Zealand
Postal address: PO Box 12441, Thorndon, Wellington
Freephone: 0800 DIABETES (0800 342 238)
Diabetes Youth New Zealand
Postal address: P.O. Box 56172, Dominion, Road Auckland
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Ministry of Health (2016). 2014/15 New Zealand Health Survey: Adult data tables. Wellington: Ministry of Health. http://www.health.govt.nz/publication/annual-update-key-results-2014-15-new-zealand-health-survey [Accessed: 19/10/16]
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Created: October 2016