{"id":159619,"date":"2026-07-20T13:27:34","date_gmt":"2026-07-20T13:27:34","guid":{"rendered":"https:\/\/pabau.com\/?p=159619"},"modified":"2026-08-13T13:04:36","modified_gmt":"2026-08-13T13:04:36","slug":"glucose-tolerance-test","status":"publish","type":"post","link":"https:\/\/pabau.com\/es\/blog\/glucose-tolerance-test\/","title":{"rendered":"Glucose tolerance test: What it is, preparation, and results"},"content":{"rendered":"
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A glucose tolerance test (GTT) measures how your body processes sugar after drinking a glucose solution, used to diagnose type 2 diabetes, prediabetes, and gestational diabetes.<\/p>\n <\/div>\n

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Standard preparation requires an 8-12 hour overnight fast; patients must avoid strenuous activity and disclose all current medications beforehand.<\/p>\n <\/div>\n

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ADA thresholds for the 2-hour OGTT: below 140 mg\/dL is normal, 140-199 mg\/dL indicates prediabetes (impaired glucose tolerance), and 200 mg\/dL or above indicates diabetes.<\/p>\n <\/div>\n

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Practice management software like Pabau offers lab management and digital forms tools that help clinics streamline GTT ordering, patient preparation instructions, and result documentation in one place.<\/p>\n <\/div>\n <\/div>\n <\/div>\n \n\n\n

About 115.2 million American adults \u2014 more than 2 in 5 \u2014 have prediabetes, and more than 8 in 10 of them don’t know it, according to the CDC’s National Diabetes Statistics Report<\/a>. The glucose tolerance test is one of the most direct tools clinicians have to catch this early.<\/p>\n\n\n\n

It doesn’t just flag elevated fasting glucose. It reveals how effectively the body clears a standardized sugar load, exposing insulin resistance that a routine fasting test can miss entirely.<\/p>\n\n\n\n

This guide covers what the glucose tolerance test (GTT) is, who needs it, how to prepare, what happens during the procedure, how to read results, and what the pregnancy-specific protocols involve. It’s aimed at practitioners ordering GTTs and patients preparing for one.<\/p>\n\n\n\n

Whether you’re in a metabolic health clinic<\/a> or a GP practice managing routine diabetes screening, the clinical and workflow essentials are here.<\/p>\n\n\n\n

What is a glucose tolerance test?<\/h2>\n\n\n\n

A glucose tolerance test (GTT) measures how efficiently the body metabolizes glucose after ingesting a fixed sugar load. The patient drinks a standardized glucose solution, and blood is drawn at set intervals to track how plasma glucose rises and then falls back to normal. The pattern of that rise and fall reveals whether insulin is doing its job.<\/p>\n\n\n\n

The most common form is the oral glucose tolerance test (OGTT). For non-pregnant adults, the standard protocol uses a 75g glucose load with blood drawn at fasting baseline and again at 2 hours. During pregnancy, a different protocol applies, covered in detail below.<\/p>\n\n\n\n

The GTT differs from a routine fasting blood glucose test in one critical way: it tests dynamic glucose metabolism under a measured glucose load, not just the resting state. A patient can have a normal fasting glucose yet still show impaired clearance on a GTT. That pattern is typical of early insulin resistance and prediabetes.<\/p>\n\n\n\n

Why is a glucose tolerance test ordered?<\/h2>\n\n\n\n

Clinicians order the GTT when a patient’s clinical picture suggests impaired glucose metabolism but a fasting glucose test alone isn’t conclusive. Common indications include:<\/p>\n\n\n\n