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The oral glucose tolerance test involves measuring blood glucose levels on an empty stomach and 2 hours after consuming a glucose solution. This test is used to diagnose various carbohydrate metabolism disorders, including diabetes mellitus, impaired glucose tolerance (IGT), and fasting glucose abnormalities.

Screening Recommendations for Carbohydrate Metabolism Disorders:

Age/Group

                Target Groups  

       Frequency

> 45 years

     Normal body weight, no risk factors

Every 3 years if results are normal

Adults with BMI > 25

+ at least 1 risk factor

Every 3 years if results are normal

                                                          

 

Annually if impaired glucose tolerance is detected

Contraindications for the Glucose Tolerance Test:

  • Acute conditions, including infectious diseases.
  • Use of medications that increase blood glucose levels, such as glucocorticoids, thyroid hormones, thiazides, beta-blockers, or oral contraceptives (discontinue 3 days before the test if medically approved).
  • Pregnancy beyond 32 weeks. Testing is preferred between 28–32 weeks of gestation under strict medical supervision.

Test Procedure:

  1. After fasting overnight (8–14 hours), a blood sample is collected.
  2. The patient consumes 75 g of glucose dissolved in 250–300 mL of water (or 82.5 g glucose monohydrate) within 5 minutes.
    • For children: 1.75 g of glucose per kg body weight (or 1.925 g glucose monohydrate per kg).
    • Children over 43 kg receive the standard adult dose.
  3. Blood glucose is measured 2 hours after glucose intake.

Diagnostic Criteria for Diabetes:

  • Fasting blood glucose consistently above 7 mmol/L.
  • Blood glucose >11.1 mmol/L 2 hours after the glucose load.

Intermediate Results:

  • Blood glucose between 7.8–11.1 mmol/L after the glucose load is considered impaired glucose tolerance (prediabetes).

Pathophysiology of Impaired Glucose Tolerance:
Impaired glucose tolerance results from:

  1. Defective insulin secretion.
  2. Decreased tissue sensitivity to insulin (increased resistance).

Fasting blood glucose may be normal or slightly elevated in patients with impaired glucose tolerance. About 30% of individuals with this condition may see normalization of glucose tolerance over time, but they remain at high risk for developing diabetes and cardiovascular diseases.

Clinical Implications:

  • Impaired glucose tolerance often occurs as part of metabolic syndrome, which includes risk factors like high blood pressure, elevated cholesterol, and insulin resistance.
  • Early detection and intervention, such as weight loss, healthy eating, and physical activity, can prevent or delay the progression to diabetes.

Interpretation of OGTT Results (2 Hours Post-Load):

  • <7.8 mmol/L: Normal glucose tolerance.
  • 7.8–11.0 mmol/L: Impaired glucose tolerance (prediabetes).
  • >11.1 mmol/L: Diabetes mellitus.

Early detection of glucose metabolism disorders through OGTT helps guide preventive measures and reduce the risk of diabetes and its complications.

 

  • İstifadə olunan biomaterial:venoz qan
  • Peroral qlükozaya tolerantlıq test səhər,ən azı  3 gün qeyri-məhdud qidalanmadan(150 qrdan çox karbohidrat/sutkada) və adi fiziki gərginlik fonunda aparılır.Testdən qabaq 8-14 saatlıq ac qalmaq lazımdır(su içmək olar)
  • Axırıncı axşam qidanın tərkibində 30-50 qr karbohidrat olmalıdır.
  • Müayinəyə 10-15 saat qalmış alkoqol qəbul etmək olmaz
  • Gecə,testdən qabaq və test zamanı siqaret çəkmək olmaz.
  • Sample Type: Venous blood.
  • The oral glucose tolerance test (OGTT) is performed in the morning after at least three days of unrestricted diet (over 150 g of carbohydrates per day) and normal physical activity.
  • A fasting period of 8–14 hours is required before the test (water is allowed).
  • Dinner on the evening prior to the test should include 30–50 g of carbohydrates.
  • Avoid alcohol consumption 10–15 hours before the test.
  • Do not smoke the night before, during, or immediately before the test.
  • Overweight or obesity (BMI >25 kg/m²).
  • Family history of diabetes (close relatives with the condition).
  • Women with a history of:
    • Pregnancy ending in premature delivery.
    • Birth of a baby weighing >4.5 kg.
    • Congenital anomalies.
    • Stillbirth.
  • Patients over 45 years old.
  • Metabolic syndrome.
  • Chronic liver diseases.
  • Atherosclerosis, gout.
  • Polycystic ovary syndrome (PCOS).
  • Neuropathies of unknown etiology.
  • Long-term use of diuretics, glucocorticoids, or synthetic estrogens.
  • Chronic periodontitis and recurrent boils.
  • Low physical activity.
  • Fasting glycemia or history of impaired glucose tolerance.
  • Hypertension of various origins or cardiovascular diseases.
  • Lipid metabolism disorders: HDL <0.9 mmol/L or triglycerides >2.82 mmol/L.

Contraindications

  • Repeated testing is unnecessary if fasting blood glucose exceeds the diagnostic threshold of 7 mmol/L.
  • Testing is contraindicated in patients with fasting glucose levels >11 mmol/L.
  • The test should not be performed in patients who have recently undergone surgery, a myocardial infarction, or childbirth.
  • The test can be used to evaluate the insulin secretory reserve by comparing fasting glucose levels with levels 2 hours post-glucose load.

OGTT is a valuable diagnostic tool to detect and monitor glucose metabolism disorders and guide early intervention.