Fasting Hyperglycaemia – Causes, Symptoms & Treatment
Fasting hyperglycaemia refers to elevated blood glucose levels measured after at least 8 hours without food intake. It can indicate diabetes mellitus or a prediabetic condition.
Things worth knowing about "Fasting hyperglycaemia"
Fasting hyperglycaemia refers to elevated blood glucose levels measured after at least 8 hours without food intake. It can indicate diabetes mellitus or a prediabetic condition.
What is Fasting Hyperglycaemia?
Fasting hyperglycaemia is defined as an abnormally high blood glucose (blood sugar) level measured after a fasting period of at least 8 hours. According to the World Health Organization (WHO), a fasting plasma glucose level of ≥126 mg/dl (7.0 mmol/l) meets the diagnostic threshold for diabetes mellitus. Values between 100 and 125 mg/dl (5.6–6.9 mmol/l) are classified as impaired fasting glucose (IFG), commonly referred to as prediabetes.
Causes
Fasting hyperglycaemia can result from a variety of underlying conditions and risk factors:
- Insulin resistance: Body cells fail to respond adequately to insulin, impairing glucose uptake.
- Reduced insulin secretion: The pancreas does not produce sufficient insulin to maintain normal blood glucose levels.
- Increased hepatic glucose production: The liver releases excessive glucose into the bloodstream, a phenomenon sometimes referred to as the dawn phenomenon.
- Medications: Corticosteroids, certain antihypertensives, and atypical antipsychotics can raise blood glucose levels.
- Hormonal disorders: Conditions such as Cushing syndrome, acromegaly, or phaeochromocytoma can cause elevated fasting glucose.
- Stress and infections: Stress hormones such as cortisol and adrenaline stimulate glucose release.
- Genetic predisposition and obesity: Visceral adiposity is strongly associated with insulin resistance and elevated fasting glucose.
Symptoms
Mildly elevated fasting glucose often causes no noticeable symptoms. When values are significantly elevated, the following may occur:
- Excessive thirst (polydipsia)
- Frequent urination (polyuria)
- Fatigue and general malaise
- Blurred vision
- Difficulty concentrating
- Impaired wound healing
Because symptoms are often non-specific or absent entirely, fasting hyperglycaemia is frequently detected incidentally during routine blood tests.
Diagnosis
Diagnosis is made by measuring fasting plasma glucose from venous blood after at least 8 hours of fasting. Additional tests may be used to confirm and characterise the condition:
- Oral glucose tolerance test (OGTT): Blood glucose is measured 2 hours after consuming a standardised glucose solution.
- HbA1c: Reflects average blood glucose levels over the preceding 2–3 months.
- Repeat measurement: An elevated result should be confirmed on a separate day before a diagnosis is established.
Treatment
Management of fasting hyperglycaemia depends on the underlying cause and the severity of the elevation:
Lifestyle Modifications
- Dietary changes: Reducing rapidly absorbed carbohydrates and adopting a fibre-rich or Mediterranean-style diet.
- Regular physical activity: Both aerobic and resistance exercise improve insulin sensitivity.
- Weight loss: Even moderate weight reduction can significantly improve fasting glucose levels.
- Stress management: Relaxation techniques can help lower stress hormone levels.
Pharmacological Treatment
- Metformin: The most commonly used first-line medication for type 2 diabetes and prediabetes.
- Other oral antidiabetic agents: Including SGLT-2 inhibitors, GLP-1 receptor agonists, and DPP-4 inhibitors.
- Insulin therapy: Required in advanced type 1 or type 2 diabetes mellitus when other treatments are insufficient.
References
- World Health Organization (WHO): Definition and Diagnosis of Diabetes Mellitus and Intermediate Hyperglycaemia. WHO Press, Geneva, 2006.
- American Diabetes Association (ADA): Standards of Medical Care in Diabetes 2024. Diabetes Care, 2024; 47 (Suppl. 1).
- Kasper, D.L. et al. (Eds.): Harrison's Principles of Internal Medicine, 21st Edition. McGraw-Hill Education, New York, 2022.
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