What is diabetes and what causes it?
Diabetes is a group of metabolic diseases characterized by prolonged high blood glucose levels, resulting from defects in insulin secretion, insulin action, or both. There are two main risk factors.
The first is genetics — having a parent or sibling with diabetes increases your own risk.
The second, and more significant, factor is lifestyle: eating excessive amounts of sugary foods, refined carbohydrates, and high-fat foods, combined with physical inactivity and a sedentary lifestyle, promotes obesity and excess body weight, which are major drivers of the disease.
Excess body fat leads to a condition called insulin resistance. Normally, the pancreas releases insulin to keep blood sugar within a normal range. When obesity is present, accumulated fat impairs insulin’s ability to function properly. Over time, the pancreas itself — constantly exposed to high blood sugar — becomes damaged and produces less insulin, eventually requiring the patient to use insulin injections.
What are the symptoms of diabetes?
This refers specifically to Type 2 diabetes, the most common form. Symptoms may or may not be present, and when they do appear, they vary in number and severity from person to person. Because Type 2 diabetes develops slowly — sometimes over many years — it is often called a “silent threat.” Symptoms can include:
- Excessive thirst — when blood sugar exceeds 180 mg/dL, the body tries to flush out sugar through urination, causing fluid loss and triggering thirst
- Frequent urination, especially at night
- Urine that attracts ants (a sign of sugar in the urine)
- Frequent hunger and increased appetite — because insulin cannot deliver glucose to the body’s organs for energy, the body breaks down fat and muscle instead, causing fatigue, hunger, and weight loss
- Unexplained weight loss
- Slow-healing wounds, frequent skin infections, and recurring abscesses — high blood sugar reduces the ability of white blood cells to fight infection
- Itchy skin and susceptibility to fungal infections, caused by dry skin or inflammation common in diabetics
- Burning, tingling, or numbness in the hands and feet
- Blurred vision — from blood sugar changes affecting the eye lens, cataracts, or diabetic retinopathy
- Leg pain or cramping when walking long distances
- Numbness or abnormal sensation in the fingertips or feet, and sexual dysfunction — caused by nerve damage from prolonged high blood sugar, which also increases the risk of foot ulcers
- Darkened, thickened skin at the neck, armpits, or stretch marks on the abdomen
- Chronic vaginal discharge or itching in women
In mild cases, where blood sugar ranges between 126–200 mg/dL, there may be no obvious symptoms, and the condition is often discovered incidentally during a urine test or routine health check.
What complications can diabetes cause?
Uncontrolled diabetes leads to serious long-term complications affecting multiple organs:
- Chronic kidney failure — diabetes gradually impairs kidney function; if poorly managed, it can progress to end-stage renal disease
- Blindness — retinal degeneration causes blurred vision, dark spots, and, if untreated, complete vision loss
- Nerve damage and limb amputation — numbness, particularly in the hands and feet, makes patients vulnerable to unnoticed wounds that can progress to the point of requiring amputation
- Arterial hardening (atherosclerosis)
- Foot ulcers
- Autonomic nervous system complications — including urinary incontinence, bloating, constipation, and reduced sexual function
What are the risk factors for developing diabetes?
The following factors increase the risk of diabetes:
- Age 35 and above — insulin synthesis and secretion naturally decline with age
- Obesity or BMI over 25, physical inactivity, and chronic stress — all reduce insulin sensitivity
- A parent or sibling with diabetes
- High blood pressure (BP over 140/90 mmHg)
- Cardiovascular disease or arterial narrowing (coronary artery disease, stroke, or peripheral artery disease)
- Pancreatic disease such as pancreatitis, or a history of pancreatic surgery
- A history of impaired glucose tolerance (IGT) or impaired fasting glucose (IFG)
- Conditions associated with insulin resistance, such as polycystic ovarian syndrome (PCOS) or acanthosis nigricans (dark, thickened skin at the neck or armpits)
- Previous infection with certain viruses such as rubella or mumps, which can damage the insulin-producing cells of the pancreas
- Use of certain medications such as steroids, diuretics, or some contraceptive pills
- Low HDL cholesterol or triglycerides above 250 mg/dL
- Women with a history of gestational diabetes or delivering a baby weighing over 4 kg
- Physical inactivity
- High-risk ethnicities such as South Asians and Pacific Islanders
Anyone with at least one of these risk factors should be screened for diabetes early and retested every one to three years depending on the level of risk.
What are the different types of diabetes?
Diabetes is classified into four types:
Type 1 diabetes (insulin-dependent) occurs when the immune system attacks and destroys the insulin-producing cells of the pancreas, leaving the body unable to produce insulin. It can occur at any age but is most common in children and young adults under 30. Patients are typically thin and must be treated with insulin injections. Without insulin, a life-threatening condition involving high blood sugar and ketoacidosis can develop. In Thailand, Type 1 accounts for approximately 3.4% of all diabetes cases.
Type 2 diabetes (non-insulin-dependent) accounts for 95–97% of all diabetes cases in Thailand. It typically affects overweight adults over 40 whose pancreas still produces some insulin, but whose body has become resistant to it. Over time, the insulin-producing cells of the pancreas deteriorate, worsening blood sugar control. A family history of diabetes increases the risk. Type 2 is increasingly being seen in children — particularly obese children — due to changing lifestyles characterized by high-fat diets, lack of exercise, and excessive screen time.
Other specific types have identifiable individual causes and are relatively uncommon. Examples include diabetes caused by alcohol-related pancreatitis destroying insulin-producing cells, or steroid-induced insulin resistance. This category also includes diabetes caused by genetic abnormalities, hormonal disorders, or certain drugs and chemicals.
Gestational diabetes occurs during pregnancy in women with no prior history of diabetes. Hormones produced by the placenta counteract insulin, reducing the body’s response to it. If the pancreas cannot compensate by producing enough additional insulin, gestational diabetes develops. It usually resolves after delivery, but women who experience it have a significantly elevated risk of developing Type 2 diabetes later in life and should be monitored regularly.
What should you do if you are found to have high blood sugar?
Consult a doctor promptly and avoid foods high in sugar, fat, and refined carbohydrates. Cut out soft drinks and alcohol, and commit to regular physical activity.
How is diabetes diagnosed?
Normal fasting blood sugar in a healthy person is 70–99 mg/dL, and blood sugar two hours after eating should not exceed 140 mg/dL. Diabetes is diagnosed using three methods:
The first and most common method is a fasting blood glucose test. A result below 100 mg/dL is normal, 100–125 mg/dL indicates prediabetes, and 126 mg/dL or above on at least two occasions confirms diabetes. A blood sugar of 200 mg/dL or above at any time, combined with symptoms, also confirms diabetes.
The second method measures the average accumulated blood sugar over three months — known as HbA1c. A level below 5.7% is normal, 5.7–6.4% indicates prediabetes, and 6.5% or above indicates diabetes.
The third and most detailed method is the oral glucose tolerance test (OGTT), in which the patient drinks 75g of glucose solution and has blood drawn after two hours. A two-hour result of 140–199 mg/dL indicates impaired glucose tolerance (prediabetes), and 200 mg/dL or above confirms diabetes.
How is diabetes treated?
Treatment has two main goals: keeping blood sugar within a normal range to prevent short-term symptoms such as dizziness, palpitations, and fainting from low sugar or confusion and loss of consciousness from high sugar; and preventing long-term complications such as
- Blindness from diabetic retinopathy
- Kidney failure requiring dialysis from diabetic nephropathy
- Heart attack
- Coronary artery disease
- Stroke or paralysis
- Infected foot ulcers
- Poor blood circulation to the legs
Treatment is built on three pillars:
Medical nutrition therapy and lifestyle modification — adjusting diet and increasing exercise. A landmark US study found that behavioral changes involving a 7% reduction in body weight and 150 minutes of weekly exercise reduced the incidence of diabetes by 58%, compared to 31% with medication alone — making lifestyle change more effective than drugs.
Medication — including oral tablets, weekly injectable medications, and insulin injections. Multiple medications may be used together when blood sugar is very high. As control improves, the number and dose of medications can often be reduced, and in some patients medication can be stopped entirely. All diabetes medications are safe for the liver and kidneys in the long term; some even reduce the risk of heart disease, stroke, kidney failure, and poor circulation in the legs.
Regular follow-up appointments — including annual comprehensive physical examinations, fasting blood glucose and HbA1c checks, foot and peripheral nerve assessments, eye examinations with pupil dilation, ECG, dental check-ups every six months, kidney function and microalbumin urine tests, blood lipid panels, dietary and exercise reviews, and annual flu vaccination plus pneumococcal and hepatitis B vaccines.
What acute and chronic complications can diabetes cause?
Acute complications develop rapidly and require urgent treatment:
- Loss of consciousness from dangerously high blood sugar (with or without ketoacidosis)
- Loss of consciousness from low blood sugar
- Serious infections
Chronic complications develop over years due to progressive narrowing and hardening of blood vessels throughout the body:
- Heart disease — 2 to 4 times the risk of the general population
- Stroke — 5 times the risk
- End-stage kidney failure — 20 times the risk
- Blindness from retinal and lens degeneration — 25 times the risk
- Peripheral arterial disease and nerve damage in the feet — leading to ulcers and, in some cases, amputation
- Autonomic nervous system damage — causing dizziness, digestive problems, bowel irregularities, and reduced sexual function
Diabetes is a chronic condition with no complete cure, but with proper self-care and education, blood sugar can be kept within a healthy range, complications can be delayed, and patients can live a full and normal life.
