Diabetes Mellitus

According to statistics, there are more than 410 million people suffer from diabetes mellitus around the world. It is expected that the number will rise to 640 million in 2040. Currently, there are some 700,000 people with diabetes mellitus in Hong Kong, representing 10% of the total population, which means that in every 10 people in Hong Kong, there is one people with diabetes mellitus. And the number is increasing sharply. The prevalence ranges from 2% in people aged less than 35 years to more than 20% in those older than 65 years.


Diabetes mellitus is a chronic disease with disordered metabolism. When we are having carbohydrates (including sugar and starch, etc.), such materials become dextrose after digestion and become glucose as they are absorbed into blood circulation system by the small intestine. The pancreas secretes insulin, helping the glucose to enter into cells for use.

Glucose level rises when there is insufficient insulin secretion or the body cannot make use of the insulin produced normally. Hyperglycaemia can result in disturbance of fat and protein metabolism, and destruction of varies systems and organs, including: cardiovascular, retina, nerves and kidneys in the long term.

Standard of blood glucose value

  Fasting glucose
< 5.6 mmol/L ≥5.6 to < 7 mmol/L ≥7 mmol/L
2 Hours after Meal < 7.8 mmol/L Normal Impaired Fasting Glucose Diabetes
≥7.8 to < 11.1 mmol/L Impaired Glucose Tolerance Impaired Glucose Tolerance Diabetes
≥11.1mmol/L Diabetes Diabetes Diabetes

Note: ADA recommended that the normal level of fasting glucose should be less than 5.6 mmol/L. If the level of fasting glucose is equal or higher 5.6 to < less than 7 mmol/L, it should be considered as impaired fasting glucose

Impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) mean the in-between of normal glucose regulation and diabetes mellitus glucose level, i.e. the pre-diabetes mellitus state. Studies show that a patient under the condition of IGT is more likely to suffer from cardiovascular disease than normal people.

According to the standards of the World Health Organization, if the fasting* glucose is higher than 7 mmol/L or the 2-hour glucose level is higher than 11.1 mmol/L, such case could be diagnosed as diabetes mellitus.
*Fasting is defined as 8 hours or above of nil by mouth
Add HbA1c level from ADA as below

The similar concept of IGT and IFG


People with one or more of the categories below are more likely to suffer from diabetes mellitus:

  • whose immediate family member suffers from diabetes mellitus;
  •  who suffers from hypertension or hyperlipidemia (excessively high level of lipids in blood);
  • women who has history of gestational diabetes mellitus (a type of diabetes mellitus that occurs only during pregnancy) or gave birth to overweighted baby (weighting 4 kg or above);
  • who is obese (with BMI over 23);
  • who is in the middle age (aged 45 or above), etc.

Obesity is the primary risk factor of diabetes mellitus. Thus, we could lower the risk of diabetes mellitus by preventing obesity. Some prevention methods are suggested below:

  • keeping ideal weights. Those who are overweighed shall set out weight-losing target (5-10% of the current body weight)
    • the Body Mass Index (BMI) of Asians is 18.5-22.9.
    • BMI = Weight (kg) ÷ Height (m)  ÷ Height (m)
  • Balanced diet with a target of “Three lows and one high” – i.e. low fat, low sugar, low sodium and high-fiber diet principle
  • Keeping active, exercising regularly with medium intensity (it is recommended to exercise daily for 30 minutes or above for at least 5 days a week)

Since the early symptoms of Diabetes Mellitus are not obvious, proper body check every year could help detect the disease as soon as possible.


Diabetes Mellitus is generally classified into 4 categories with different causes:

  • Type 1 Diabetes Mellitus: It was called “Insulin-dependent Diabetes Mellitus”. It is related to factors of genetic and immune system which result in destruction of insulin producing cells, leaving the cells completely or severely incapable to produce insulin for the need of body. Most affected people are children and juvenile, representing 3% of the patients.
  • Type 2 Diabetes Mellitus: was called “Non-insulin-dependent Diabetes Mellitus”, which represents more than 90% of diabetes mellitus cases. It is mainly related to unhealthy diet, obesity and lack of exercise. The body cells are resistant to insulin and thus cannot uptake and use glucose effectively and excess sugar in blood is resulted. This type of diabetes mellitus has higher genetic predisposition than Type 1.​
  • Gestational Diabetes Mellitus: It is mainly due to the change in hormones produced during pregnancy and usually subsides after delivery. Studies in recent years show that women with gestational diabetes mellitus have higher risk of developing type II diabetes mellitus later on, thus such women should pay more attention to healthy diet to reduce such risk.
  • Other types of Diabetes Mellitus: There are other causes which are different from those of the above three types, including insufficient insulin secretion caused by certain genetic diseases, caused indirectly by other diseases (e.g. pancreatitis, i.e. inflammation in the pancreas), resulted from drugs or chemicals.

Some of the patients of diabetes mellitus may have the following symptoms in the early stage:

  • frequent thirst
  • frequent urination
  • frequent hunger
  • weight loss
  • fatigue
  • blurred vision
  • poor wound healing
  • itching skin, women may feel itchy in private parts

Some patients may not have any of the symptoms above, thus regular body check is recommended to avoid delayed medication.

After taking notes of medical history of a patient, the doctor will usually perform the checks below:      
  • random blood glucose test: taking blood to check the glucose level without fasting.
  • fasting blood glucose test: fasting after midnight and taking blood to check the glucose level the next morning.
  • 75g oral glucose tolerance test: after taking fasting blood glucose test, the patient is given 75g of glucose and blood glucose is drawn after 2 hours for observation of the change of blood glucose.
  • Hba1c testing

Currently there is no cure to diabetes mellitus. Patients should follow the treatment to control the disease and reduce the risk of complications. Patients should comply to different kinds of treatment according to the type and severity of diabetes mellitus.

Dietary treatment
All diabetic patients should follow dietary treatment. Different people have different calorie requirement, patients should consult registered dietician to design a suitable menu for the management of the disease and stabilizing blood glucose. The general principles are as follow:

  • balanced diet, regular meal time and amount following the principle of “eat less and more meals” for stabilizing blood glucose.
  • appropriate amount of food containing carbohydrate (including grains, rhizome vegetables, fruits and dairy products).
    • Carbohydrate should be around 50% of the total calorie intake. For example, around 750 kcal of calorie (equivalent to around 188g carbohydrate, i.e. of 18 - 19 portions of carbohydrate exchange) to be produced by carbohydrate in a 1500 kcal menu.
    • The above carbohydrate exchange should be distributed evenly in main meals and snack time, e.g.: 5 portions for each of the breakfast, lunch and dinner and 1 portion for the snack time between meals. 1 portion of carbohydrate exchange = 10g of carbohydrate.
    • Patients can choose suitable amount of grains, rhizome vegetables, fruits and dairy according to “carbohydrate exchange”, e.g.:
      • 1 portion of grains (10g carbohydrate) = 
        a)    a full soup spoon of rice / rice vermicelli/Shanghai noodles (cooked) 
        b)    1/3 bowl of macaroni/spaghetti (cooked)
        c)    1/2 bowl of oat meal (cooked) (1 bowl = 300ml medium bowl)
        d)    1/5 bowl of Chiuchow style congee / 
        e)    1/2 sliced of bread (without fringe) 
      • 1 portion of rhizome vegetables (10g of carbohydrate) = potato/sweet potato with the size of an egg / pumpkin/lotus root with the size of 2 eggs
      • 1 portion of fruit (10g of carbohydrate) = a small apple/orange/tangerine/pear/kiwi fruit / 1/2 large apple/orange / 10 small grapes / 1/2 banana
      • 1 portion of dairy product (12g of carbohydrate) = 240ml of low fat/skimmed milk / 4 soup spoons of skimmed milk powder
  • Avoid food and drinks with rich sugar or additional sugar to prevent surge of glucose.
  • Avoid too much fat (especially saturated fat such as animal skin and grease) to protect the cardiovascular system.
  • Avoid drinking too much alcohol. It is because alcohol can increase the risk of side effects from medications and may lead to low blood glucose. In addition, drinking alcohol with empty stomach should be avoided. If one cannot avoid it, consumption should be limited to less than 2 portions of alcohol for men and less than 1 portion for women every day (1 portion is equal to 300ml of beer / 150ml of red wine / 45ml of spirit).

Oral Anti-Diabetic Drugs (OAD)​
Prescriptions will be given by doctor according to the pre-existing diabetic complications, body condition, drug reactions and condition of blood glucose control of individual patient.

Type  Function   Example
Sulfonylureas Stimulate the insulin secretion of pancreas  Tolbutamide
Gliclazide MR
Biguanides Reduce the production of glucose in liver, increase the application of glucose by body tissue (muscles) and reduce the absorption of glucose in gastrointestinal tract Metformin
Metformin XR
 α-Glucosidase Inhibitors  Slow down the absorption of dextrose in small intestine so as to prevent too much glucose after meals  Acarbose
Glitazones Increase the sensitivity of body to insulin so glucose would enter into the cells and decrease the glucose level. Pioglitazone
Dipeptidyl Peptidase-4 Enzyme Inhibitors  Stimulate the insulin secretion of pancreas   Sitagliptin
Meglitinides / Glinides Stimulate the insulin secretion of pancreas Repaglinide
SGLT2-inhibitors Inhibit reabsorption of glucose in the kidney and lower blood sugar; e.g. empagliflozin, dapagliflozin Dapagliflozin Empagliflozin
Injection of insulin
Injection of insulin is a way similar to the normal secretion of insulin to manage glucose. This treatment is applied to type 1 patients and type 2 patients whose glucose level cannot be managed after application of oral anti-diabetic drugs and pregnant diabetic patients.

Insulin injections can be classified into 5 different types according to the onset and length of action, including rapid-acting, short-acting, intermediate-acting, long-acting and pre-mixed combination insulin. The doctors will generally decide the type, dose, and the frequency of injection required. Insulin injection can be done by the patients themselves after training by healthcare professionals.

Incretins Mimetic
Glucagon-like peptide-1 Receptor Agonist (GLP-1RA) is a newer medication, with similar effect as incretin in our intestine. GLP-1 RA increases the secretion of insulin for the control of blood glucose.


Acute complications

• Acute Hypoglycemia (Blood glucose <3.9mmol/L)Patients may have cold sweat, shakiness, pallor, racing heartbeat, drowsiness or even unconsciousness. If the patient is conscious, 15g of simple carbohydrate can be applied, e.g. 3 lumps of cube sugar/ fruit candies, or 1/2 glass of normal soft drinks/fruit juice, and take15g complex carbohydrate eg. a small piece of bread or 3-4 biscuits after the symptoms are improved.

• Acute Hyperglycemia (abnormally high level of blood sugarBlood glucose >15mmol/L)
Patients may experience deep and rapid breathing, nausea, vomiting and excessive thirst, and may lead to unconsciousness or coma. Patients must be admitted to hospital as soon as possible.

Chronic complications
If diabetes mellitus is not adequately controlled and glucose level remains high over a prolonged period, blood vessels and nervous system are easily impaired and can result in long-term damage or even failure of body organs.



Brain  Cerebrovascular disease, e.g. stroke
Eyes  Retinopathy, cataract, glaucoma
Heart and blood vessels  Coronary artery disease, heart failure, high blood pressure
Kidneys  Proteinuria, infection, kidney failure
 Foot  Neuropathy, vasculopathy, ulcer, infection
(Those who suffer from long-term ulcer of lower limbs may need amputation)

Ideal glucose control can reduce complications. The conditions of glucose control could be known by the following methods:

1) Glycated Haemoglobin A1c (HbA1c)
Haemoglobin is a protein found in red blood cells which carries oxygen to body tissues and carbon dioxide away from body tissue. Glucose in blood can attach to haemoglobin. Since red blood cell has an average life span of about 3 months, the average glucose level in the last 2-3 months of patients can be shown by measuring of HbA1c.

The ideal HbA1c level should be kept below 6.5%. Studies show that 1% decrease in HbA1c could reduce the risk of death of diabetes mellitus by 21% and diseases of capillary (e.g. retinopathy, kidney failure, etc.) by 37%.

2) Blood glucose value of fasting and after meal

 Blood glucose value (mmol/L)  Ideal   Normal   Poor
 Fasting  4.0-6.0  <8.0  >10.0
 2 hours after meal  <8.0  <10.0  >12.0

Researches show that if patients could monitor glucose regularly by themselves, blood glucose could be better controlled and reduce the risk of complications.

Through proper learning classes and other means, patients should learn and commit to self-manage their illness, including the following aspects:

  • Illness control
    • Follow diabetes mellitus diet principles
    • Monitor glucose condition at home, e.g. glucose test by themselves
    • Take medicatins timely and understand the effects and potential side effects of drugs
    • If need to use insulin injection, understand the technique of insulin injecrtion
    • Exercise everyday and control body weight
  • Complication prevention
    • Understand the symptoms, prevention and management of hypoglycaemia
    • Foot care, keep your feet dry and clean, wear protective footwear and avoid injury
    • Oral care, regular dental examination and prevent infection
    • Monitor blood pressure and blood lipid, detecting problems in the early stage
    • Quit smoking and alcohol to reduce the risk of complications
  • Wear a hand band or carry a card indicating that you are diabetic.
  • Attend regular follow-up consultations and assessments, detecting and managing complications in the early stage.
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