Diabetes mellitus is a condition in which patients have high blood sugar. It is a common condition and affects 8.6% of the population in Singapore. This is an increase from 4.7% in 1984. It is an important condition because there are many complications that can occur as a result of diabetes mellitus. These can be divided broadly into those that occur in the short term (the acute complications) and those that occur over a long time (the chronic complications).

Before we go into details of these complications, there is one very important message that we must get across to you as patients and members of the public. These complications are preventable. Although this is not true in every case, well controlled diabetes mellitus through your own efforts and working with your doctor and other health workers, will at least delay the onset of these complications. Patients with diabetes mellitus can live healthy, active, rewarding lives.

Types of Diabetes Mellitus

There are 2 major types of diabetes mellitus.

Type 1 diabetes mellitus has also been known as juvenile-onset diabetes mellitus or insulin dependant diabetes mellitus. This is the less common type and usually occurs in young persons below the age of 35. In this condition, the body is unable to produce insulin. Insulin is a hormone produced by the pancreas, a gland that is in the abdomen. Insulin is a hormone that controls the use of different fuels for energy. It is especially important because it allows the body to use glucose (simple sugar) instead of fats. When there is no insulin, the body cannot use or store the glucose that comes from food and this causes the blood sugars to become very high. Instead, the body uses fat as a source of fuel giving rise to some of the acute complications of diabetes mellitus.

Type 2 (adult-onset or non-insulin requiring) diabetes mellitus is much more common and is the type of diabetes that affects most Singaporeans. In this type of diabetes, there is no shortage of insulin (at least at the start of the disease). Instead, the cells and tissues of the body are unable to respond to the insulin produced by the pancreas. They have "insulin resistance." (see cartoon below).

You can prevent diabetic ketoacidosis by taking your insulin and medication regularly, especially when you are sick. When you are unwell, you should monitor your blood sugar frequently and give additional insulin when the blood sugar is high. Your doctor or diabetes nurse educator should be able to give you some advice on how to make these adjustments. If you are unable to eat, you should see your doctor as you may need to be put on a drip until you recover from your illness.

Compared to diabetic ketoacidosis, which can occur very quickly, hyperosmolar non ketotic coma occurs more gradually. You may feel thirst and pass large volumes of urine. This will result in your becoming more and more dehydrated. You will feel tired and may lose weight. Usually the urine ketones are negative or present only in small quantities. Patients may become more and more drowsy and become unconcious. This condition is more common in type 2 diabetes mellitus and may occur because of insufficient medication. More commonly, it occurs due to some other illness or injury such as infection. Once again, if the blood sugar is very high and you feel very unwell, it is important to consult you doctor quickly as this is also a diabetic emergency.

Apart from the acute diabetic emergencies, high blood sugar does not cause death or disabilty in itself. Most of the disability from diabetes mellitus results from the chronic complications of diabetes mellitus and we stress again, these are preventable.

The complications of diabetes mellitus affect many organs in the body and these include the eyes, heart, feet, kidneys, and the nervous system.

Eye disease in diabetes mellitus
Diabetes mellitus can affect the eye in many ways. Cataracts and glaucoma are more common in patients with diabetes mellitus. In addition, it can affect the part of the eye at the back which is responsible for sensing light and colour, the retina. In the retina, small vessels become "leaky" resulting in the formation of exudates, which are the yellow areas seen in the picture below. If these exudates are too close to the most sensitive area of the retina, the macula, this can impair your vision.

Diabetes mellitus also causes weakness in the blood vessel walls causing them to bulge and form microaneurysms. Generally, all persons with diabetes mellitus develop some of these microaneurysms or exudates if they have diabetes for a sufficient length of time. Unless the exudates are very close to the macula, they and the microaneuryms are harmless and will not impair your vision. We call this "background retinopathy." In fact, almost all persons who have diabetes mellitus for 20 years have changes that are due to background retinopathy.

Patients who have diabetes mellitus can also develop "proliferative retinopathy". In these cases, new blood vessels grow on the retina. These new blood vessels are fragile and can bleed giving rise to haemorrhage in the eye and this can lead to blindness.

It is important to pick up the changes due to maculopathy and proliferative retinopathy early as laser therapy can reduce the likelihood of loss of vision. In order to make sure that this is carried out at the right time, you need to go for regular eye screening. It is recommended that you have your eyes screened when you first find out you have type 2 diabetes mellitus. If they are normal, you should continue to have screening once a year. If there are any abnormalities that require attention, your doctor will refer you to an ophthalmologist (eye specialist) for treatment. Patients with type 1 diabetes mellitus do not require eye screening until 3 years after the diagnosis has been made and then once a year thereafter.

Screening can take 2 forms. Many centres can carry out fundal photography where a photograph is taken of the back of you eye allowing a doctor to look for any changes on the retina. The photograph will serve as a permanent record. In Singapore, the polyclinics have this service available. Contact your nearest polyclinic to find out when they have this service available as there are 2 cameras that move to various polyclinics at various times of the year. When a fundal camera is not available, your doctor can look at the retina directly using an instrument called an ophthalmoscope. Most doctors who manage diabetes will have an ophthalmoscope that can be used to examine the eyes carefully. Remember that your doctor has many patients to look after and make it a point to remind him or her of the time to examine your eyes.

Diabetic eye disease is one of the reasons we must try to keep the blood sugar under strict control, the DCCT has shown us that good control of blood sugar results in less eye disease and even if you already have eye disease, it can prevent it from getting worse.

With respect to heart disease, diabetes mellitus is more than just a problem of high blood sugar. In contrast to eye and kidney disease, good blood sugar control alone is not enough to prevent the development of heart disease. Diabetes mellitus is associated with widespread abnormalities in the blood. Of particular importance to heart disease are the blood lipids, which includes cholesterol and triglyceride. High triglyceride and low HDL cholesterol (the good cholesterol) is often seen in diabetic patients. In addition, the LDL cholesterol (the bad cholesterol) in diabetics may be 10-15% higher than in non-diabetics.

Are diabetics with coronary heart disease at greater risk from morbidity and mortality?
In addition to the high risk of developing coronary artery disease, studies suggest that when diabetics develop blockage in the arteries supplying the heart, this is more extensive than in non-diabetic individuals. An acute myocardial infarction (heart attack) in patients with diabetes mellitus is associated with some special features. The risk of death following a heart attack is higher in diabetic individuals. The long term prognosis of survivors of heart attacks amongst diabetics is also less favourable than in non-diabetics. Further, patients with diabetes mellitus (DM) are more likely to have painless or unrecognised heart attack..

Can we prevent heart disease in diabetic patients?
Yes! Patients with diabetes mellitus should never smoke.

What about cholesterol lowering?
We cannot answer this question directly from the available scientific evidence at this time. There is good evidence from studies conducted in Australia and New Zealand, Norway and the United States of America, that lowering blood cholesterol levels will lower the risk of heart disease in patients with diabetes mellitus. Given the very high risk of heart disease in patients with diabetes mellitus, most doctors would agree that it is important to maintain low levels of blood cholesterol. When this cannot be achieved through changes in the diet and with exercise, it may become necessary to use drugs to lower the lipid levels. We await the results of several new studies designed specifically to answer this question in diabetics and we hope to keep you posted regarding the results. We can start to expect the results of these large studies around the year 2000.

Kidney disease in diabetes mellitus usually follows a set pattern. It begins with the appearance of small amounts of a protein called albumin in the urine. This is called microalbuminuria and can be detected using specialised tests. It is important to screen for this stage of diabetic kidney disease because aggressive treatment can normalise the kidney function at this time. Speak to your doctor about a test for urine microalbumin. As with eye disease, this stage of kidney disease produces no symptoms and you will not know you have it unless you test for it. This should be done at the time of diagnosis for type 2 diabetes mellitus and yearly thereafter. Those with type 1 diabetes mellitus can wait 3 years before doing their first test.

• Good control of your blood sugar.
• Good control of blood pressure.
• Use of drugs called Angiotensin converting enzyme inhibitors (ACE inhibitors)
• Cessation of smoking
• Control of blood lipids
• A low protein diet

Treatment of any urine infections. Patients with diabetes mellitus are especially prone to develop urine infections. If you have symptoms of pain when you pass urine, pass urine very frequently or more than twice at night or if you develop fever, you should see your doctor to test your urine for any infection so that you can be given appropriate treatment.

Do not delay or skip your meals or snacks (if allowed) as this may lead to fluctuations of your blood sugar levels. If in  doubt, you should seek medical nutrition therapy from a qualified dietitian who will help tailor a meal plan to suit your lifestyle and medical condition.

Regular exercise is an important part of diabetes control and should be part of your daily routine.

Exercise :

• Helps insulin to work better and lower your blood glucose.
• Lowers the blood pressure and cholesterol levels.
• Strengthens the heart and improves blood circulation.
• Reduces body fat and control body weight.

Select an exercise program
The type of exercise that is suitable for you depends on your age, physical fitness and preferences. You may need to consult your doctor or nurse educator when planning for an exercise program.  Choose an exercise that you would enjoy doing. Brisk walking, jogging and cycling are good examples. Exercise regularly, every day if you can or at least 3 times a week and 30 minutes for each session. Plan your programme, start slowly and gradually. Increase the amount of exercise you do each session.

Always start with warm up (stretching) for 5 – 10 minutes follow by the actual exercise, and end with cool down exercise, just as you would do for the warm up.

• Test your blood glucose before and after exercise. It is not safe to exercise if your blood glucose is above 15 mmol/L, if you are feeling unwell or if there are ketones in your urine. 
• If blood glucose is low, eat a snack.
• If blood glucose is normal, you do not need a snack unless you are doing some strenous exercise.
• Alternatively, you can reduce your insulin dose before exercise. Consult your doctor or nurse educator on what is best for you.
• Always carry quick sugar, such as glucose tablets candy etc. With you when you exercise (especially if you are on insulin). Hypoglycaemia (Low blood sugar) may occur during or after exercise due to increased transport of glucose into the muscles by insulin.
• If possible, exercise with your spouse or a friend.

Type	Example	Action	Side effect
1.Sulfonylureas