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Blood Glucose

A high fasting blood glucose level can be an indicator of underlying health problems, including diabetes and heart disease.

What is diabetes?

Diabetes occurs when the level of glucose (sugar) in your blood is too high – either because your body doesn’t produce enough insulin or your body does not effectively use the insulin that it does produce. Insulin is a hormone necessary to carry glucose from the bloodstream into the cells where it is used for energy. If there is too little insulin, or resistance to insulin, blood glucose levels continue to rise, as glucose is not removed from the bloodstream.

There are 2 main types of diabetes – Type 1 (insulin dependent) and Type 2 (also known as maturity onset or non-insulin dependent diabetes). Type 1 usually affects younger people while Type 2 tends to develop gradually in adults and is much more common. You are more likely to develop diabetes if you have one or more of the following risk factors:

  • being overweight or obese
  • physical inactivity
  • family history of diabetes
  • previous diabetes in pregnancy (gestational diabetes). 

It has been estimated that there are about 1 in 10 South Africans with diabetes, but there are many adults who have diabetes and don’t know it, because it has not been diagnosed!

How does diabetes affect your heart?

Heart disease and stroke are the leading cause of death in diabetics. The constant high blood sugar causes narrowing of the arteries, increased blood triglycerides (a type of fat), decreased levels of HDL (“good”) cholesterol, high blood pressure and heart attack. Diabetics are also more prone to the development of atherosclerosis and blood clot formation. Diabetes also increases the damage done by smoking, high blood pressure and high cholesterol.

Diabetes can even affect the heart muscle itself, making it a less efficient pump. As diabetes can affect the nerves to the heart, symptoms of angina may not be felt in the usual way and may be passed off as indigestion or a stomach upset. This leads to delays and difficulties in diagnosing angina and heart attacks. As you can see, diabetes increases the risk of stroke and heart disease, especially if other risk factors are already present. The risks multiply! The good news is that there are things that you can do to control your diabetes, reduce your risks and stay healthy.

What are the symptoms and complications of diabetes?

Some of the symptoms include: constant thirst, passing more urine than normal, tiredness, unexplained weight loss, blurred vision or regular episodes of thrush. These symptoms are a result of having too much glucose in the blood and not enough in the cells. Symptoms vary from individual to individual and elderly people may not present any symptoms.
In uncontrolled diabetes, high levels of glucose over many years can damage many different parts of the body:

  • in the heart and blood vessels it aggravates atherosclerosis (hardening and narrowing of blood vessels by fatty deposits) - causing coronary artery disease, stroke and blood circulation problems
  • in the eyes, causing reduced vision which may lead to blindness
  • kidney disease and kidney failure
  • ulcers, infections, gangrene, etc in the feet
  • In the nerves, causing loss of sensation (especially in the feet and legs), pins and needles, and impotence

how is it diagnosed?

A screening (finger prick) blood test can be done at a clinic or pharmacy to give you a snapshot of how high your blood sugar level is. However, a formal diagnosis requires a blood test and sometimes this will need to be repeated twice.

Ideally a blood glucose test should be done in the morning after not eating or drinking anything but water since the previous evening. This is called a fasting blood glucose test. A fasting blood glucose level below 5.6 mmol/l can rule out diabetes. Diabetes can be diagnosed when the fasting blood glucose level is 7 mmol/l or higher confirmed by two tests repeated on separate days within a two-week period. If the blood glucose level is between 6.0 – 6.9 mmol/L, this is called impaired fasting glucose, which means the person is at risk for future diabetes.

A random blood glucose test is a test conducted at any time of the day in a non-fasting state. This can be used to diagnose diabetes if the blood glucose value is over 11 mmo/L and there are other symptoms of diabetes present. A random blood glucose test on its own cannot rule out diabetes unless your blood glucose level is <5.6mmol/l.

Often one blood test is insufficient to confirm a diagnosis of diabetes, and the test may need to be repeated again or a doctor or nurse may request an oral glucose tolerance test, which involves drinking a sugary liquid and monitoring how blood glucose levels change over the next few hours.

A blood test for HbA1c levels can also be used to diagnose diabetes, and a level of 6.5% or above can confirm diabetes.

Although there is no cure for diabetes - with careful monitoring and healthful lifestyle changes, diabetics can avoid complications and enjoy a long, productive life. To reduce your risk of cardiovascular disease, learn all you can about the condition.


if you are a diabetic, what can you do to reduce your risk of heart disease or stroke?

  • A healthy diet and medication (if necessary) is essential for control of blood sugar.
  • Monitor and check your blood glucose levels regularly, especially if you are taking insulin. Blood glucose levels should be between 4-7 mmol/l in a fasting state. A health care professional can provide an individual target for ideal blood glucose levels two hours after a meal.
  • Give up smoking. For advice on quitting smoking, click here
  • Check your blood pressure regularly and keep it below 140/90 mmHg. If you already have high blood pressure your doctor may recommend an individual blood pressure target for you.
  • Check and manage your cholesterol levels. Your goal should be:
  • Total cholesterol under 4.5mmol/l,
  • LDL cholesterol of less than 1.80mmol/l,
  • HDL cholesterol of over 1.2mmol/l in women and over 1.0 mmol/L in men
  • and a triglyceride level of less than 1.7 mmol/l. Read more about controlling cholesterol levels here
  • Aim for a healthy weight with a BMI of less than 25, and a waist measurement of less than 80cm for women, under 94cm for men and less than 90cm for men of South Asian descent. If you are overweight, losing 5 – 10% of body weight can improve blood sugar control, blood cholesterol and blood pressure. For practical advice on weight management, click here
  • Be more physically active – aim for at least 30 minutes of moderate intensity exercise 5 days a week. Examples of such exercise can include cycling, brisk walking, swimming, dancing, water aerobics or even gardening.
  • Learn to deal with stress where possible - get the support you need and learn relaxation techniques. Click here for helpful tips on managing stress
  • Look after your feet - report any cuts or problems to your doctor or nurse as soon as possible.
  • Have an annual review with your doctor to check your long-term glucose control, blood pressure, cholesterol, weight, general circulation and that you are not developing any of the complications of diabetes


Dietary advice for managing diabetes

  • A healthy diet is one of the best ways to control blood sugar and reduce risk. Remember that a diabetic doesn’t need special products, and that choosing available healthy foods is the best approach.
  • Eat a healthy varied diet with small, regular meals, which will help to regulate your blood sugar levels.
  • Choose fibre-rich starches, like oats, whole wheat bread and brown rice, rather than refined starches, like sugary breakfast cereals, white bread and white rice. This helps with blood glucose control. Legumes are also a good source of fibre, and can be eaten at least twice a week.
  • Include fruits and vegetables as go sources of carbohydrate in your diet, but avoid fruit juices and added sugars.
  • Cut down on saturated and trans fats, which can raise cholesterol levels. These fats can be found in foods such as fatty and processed meats, chicken skin, full fat dairy products, butter, ghee, cream and hard cheeses, commercially baked goods such as pies, pastries, biscuits and crackers, fast foods and deep-fried potato/slap chips.
  • It is better to replace these fats with healthier unsaturated fats such as sunflower / canola / olive oil, soft tub margarines, peanut butter, nuts and seeds, avocado or fish. Read more about the butter versus margarine debate at http://www.heartfoundation.co.za/topical-articles/butter-or-margarine%E2...
  • Fish, especially naturally oily fish (such as sardines, pilchards, mackerel and salmon) contains healthy omega-3 fats, which can help to improve heart health. Eating this kind of fish is recommended at least twice a week. Read about the benefits of fish here (http://www.heartfoundation.co.za/topical-articles/fish-too-beneficial-go...
  • Artificial sweeteners can be used instead of sugar, and are safe when used in moderate amounts.
  • Alcohol can affect blood sugar levels, so it is recommended that it is consumed with food to prevent hypoglycaemia. For those who choose to drink alcohol should do so in moderation. Moderation equates to no more than one drink a day for women and two for men.
  • High blood pressure is commonly linked with diabetes. Too much salt in the diet can raise blood pressure. Reduce salt intake to no more than 5g (1 teaspoon) of salt a day:
  • Reduce the salt added to food during cooking and at the table
  • Foods like packet soups, stock cubes, gravies, cheese, many breakfast cereals, breads, salty snacks, processed meats and fast foods are very high in salt, so should be used sparingly. Read more salty tips to reduce salt in your diet here: http://www.heartfoundation.co.za/topical-articles/wise-about-salt

For more individualised advice, contact the Heart and Stroke Health Line. Call 0860 1 HEART (0860 1 43278) or email heart@heartfoundation.co.za