What Blood Sugar Level Indicates Diabetes?

Diabetes Mellitus (DM) is a chronic condition characterized by elevated blood sugar levels due to either an insulin deficiency or resistance to insulin action. Insulin is a hormone essential for allowing glucose to enter the body’s cells to be used as energy. When insulin is insufficient or ineffective, glucose builds up in the bloodstream, leading to hyperglycemia. Prolonged high blood sugar levels can damage blood vessels and various organs, potentially resulting in serious complications.

Types and Prevalence of Diabetes

Diabetes encompasses a group of disorders that disrupt normal blood sugar regulation and cause widespread metabolic complications. Among Thai populations, Type 2 diabetes is the most prevalent, especially among the elderly. This type is typically associated with insulin resistance and lifestyle-related risk factors.

Thailand follows the diagnostic guidelines established by the American Diabetes Association (ADA). According to these criteria:

A fasting blood glucose level (after at least 8 hours of no caloric intake) below 100 mg/dL is considered normal.
A reading between 100–125 mg/dL indicates prediabetes, a condition with increased risk of developing Type 2 diabetes.
A level ≥126 mg/dL on two separate occasions confirms a diagnosis of diabetes.

Type 2 diabetes often progresses gradually and is linked to insulin resistance—where the body’s cells no longer respond properly to insulin—and an eventual decline in insulin production by the pancreas. If left unmanaged, diabetes significantly increases the risk of cardiovascular disease, stroke, and other complications.

The Role of Insulin in Diabetes

Insulin is a vital hormone secreted by the beta cells of the pancreas. Its primary role is to facilitate the uptake of glucose into body tissues, where it is converted into energy. Without sufficient insulin—or when insulin action is impaired—glucose cannot enter cells efficiently, resulting in persistently high blood sugar levels.

Beyond affecting carbohydrate metabolism, insulin deficiency disrupts fat and protein metabolism as well, leading to systemic imbalances.

Although the precise cause of insulin deficiency or resistance is not fully understood, both genetic and environmental factors play a role. A family history of diabetes significantly increases an individual’s risk of developing the disease.

Common Symptoms of Diabetes

Early symptoms of diabetes are often subtle and may include:

Frequent hunger and thirst
Excessive urination
Fatigue and weakness
Dry, itchy skin
Blurred vision
Numbness or tingling in the feet
Unexplained weight loss
Slow-healing wounds, particularly on the feet

10 Warning Signs of Diabetes

Persistent fatigue despite adequate rest
Unexplained weight loss
Frequent urination
Increased thirst
Blurry vision without an apparent cause
Leg or knee pain
Dry, itchy skin—especially around the genitals
Recurring skin abscesses or boils
Mood swings and irritability
Slow or non-healing wounds

Is There a Link Between Obesity and Diabetes?

Yes. Obesity is a key contributor to insulin resistance. Individuals who are overweight, especially those with a genetic predisposition, are at significantly higher risk of developing Type 2 diabetes. Weight management is, therefore, a central focus in diabetes prevention and treatment.

Treatment Options

Type 1 Diabetes

Patients with Type 1 diabetes require daily insulin injections due to complete insulin deficiency. Treatment also includes strict dietary control and regular physical activity.

Type 2 Diabetes

In early stages, Type 2 diabetes can often be managed through:

A balanced diet
Regular exercise
Weight control

If lifestyle changes are insufficient, oral medication or insulin therapy may be necessary.

Gestational Diabetes

Pregnant women diagnosed with diabetes should begin prenatal care early. Managing diet and engaging in physician-recommended physical activity are crucial to preventing complications.

How Is Diabetes Diagnosed?

Physicians diagnose diabetes through a combination of:

Medical history and symptoms
Physical examination
Laboratory blood tests, including:
- Random Plasma Glucose Test
- Fasting Plasma Glucose (FPG)
- Hemoglobin A1c (HbA1c) – reflects average glucose over the past 2–3 months
- Oral Glucose Tolerance Test (OGTT)

A fasting glucose level ≥126 mg/dL or a random glucose level ≥200 mg/dL accompanied by classic symptoms (e.g., excessive thirst, frequent urination, unexplained weight loss) supports a diabetes diagnosis. If symptoms are absent, a second confirmatory test is required.

Complications of Uncontrolled Diabetes

Chronic high blood sugar can damage blood vessels and lead to serious complications, such as:

Microvascular complications:
- Diabetic retinopathy (vision problems)
- Diabetic nephropathy (kidney disease)
Macrovascular complications:
- Coronary artery disease
- Cerebrovascular disease (stroke)
- Peripheral arterial disease
Neuropathy (nerve damage)
Limb amputations
In pregnant women, diabetes increases the risk of preeclampsia and miscarriage.