Glucose tolerance test 75g (0-60-120) – laboratory test

Description

Why have a 75 g glucose tolerance test

The glucose tolerance test is an oral glucose tolerance test (OGTT). First, a fasting blood sample is taken, then you drink a solution containing 75 g of glucose, and further samples are taken after 60 and 120 minutes. The test shows how quickly your body processes a dose of sugar. It detects prediabetes and diabetes, including in some people with normal fasting glucose and HbA1c levels. According to the Polish Diabetes Association (PTD), outside pregnancy, diagnosis is based on the fasting result and the result at 120 minutes, while the measurement at 60 minutes is primarily relevant to diagnosing gestational diabetes.

When to consider this test

• fasting glucose of 100–125 mg/dl (impaired fasting glucose),
• pregnancy between weeks 24 and 28 (screening for gestational diabetes),
• risk factors for diabetes: obesity, high blood pressure, a family history of diabetes, polycystic ovary syndrome,
• 6–12 weeks after giving birth in women who had gestational diabetes,
• planning another pregnancy after having had gestational diabetes.

How to prepare

• for several days before the test, eat as usual, without following a weight-loss diet or restricting carbohydrates,
• arrive fasting: do not eat for 8–12 hours; you may drink only water,
• do not drink alcohol for 3 days before the test,
• arrive in the morning, well rested after a good night’s sleep; the test should start before 10:00,
• drink the glucose solution within 5 minutes; remain at rest at the collection point for 2 hours, without eating, smoking or walking around; allow approx. 2.5 hours for the whole procedure,
• if you take metformin for prediabetes, your doctor may advise stopping it for a week before the test; do not do this on your own.

How to interpret the result

Fasting glucose of 126 mg/dl or above requires confirmation with a second measurement on a different day; a glucose load is then usually unnecessary, but the doctor makes this decision. The ranges on the laboratory report apply.

Other tests to consider alongside this test

Additional tests to assess glucose metabolism include: glycated haemoglobin HbA1c, insulin response curve, fasting insulin, lipid profile. Read more: Badania-Medyczne.pl.

Sources: Polish Diabetes Association (PTD), Clinical recommendations for the management of people with diabetes 2026 (diagnostic criteria, OGTT procedures, criteria for gestational diabetes); ALAB laboratoria, Glucose tolerance test package (preparation, test procedure, results turnaround time); MedlinePlus, Glucose tolerance test, non-pregnant (test procedure, preparation). This information does not replace a medical consultation.