Oral Glucose Tolerance Test: The Best Test for Detecting Diabetes and Insulin Resistance

When it comes to health, there are a few things we can manage. And in the case of diabetes, or metabolic dysfunction, that is a no brainer.  So why do so many of us end up pursuing blood work that does not give us accurate results?

Type 2 diabetes is a chronic condition that affects the way your body metabolizes sugar (glucose), your body's main source of energy. In type 2 diabetes, either the body doesn't produce enough insulin or it resists insulin. Insulin is a hormone produced by the pancreas that regulates the movement of sugar into your cells. When this process isn't working effectively, glucose can build up in your bloodstream, leading to a variety of health problems.

Why HbA1c Alone May Miss Early Metabolic Issues

HbA1c (Hemoglobin A1c) indicates average blood sugar levels over the past 2-3 months.  It’s a proxy and is used for diabetes risk assessment.

The oral glucose tolerance test (OGTT) is the gold standard for measuring blood glucose levels.  Why?  Simply put, you baseline your blood work for glucose after fasting.  You then drink a 75g glucose drink and two hours later, you take the blood work to measure your blood glucose levels again to see how it processed eating the equivalent of almost 20 sugar cubes.  

20 cubes of sugar in this bottle

Could it be that the 2-hour Oral Glucose test is too time consuming for many?  Could it be that doctors take the hemoglobin A1C test as the standard, and its good enough?  I don’t know, but I like real, actionable data and for measuring glucose, nothing beats the OGTT.  The OGTT measures blood glucose levels, meaning how much sugar remains in the bloodstream rather than being taken up by the cells for energy.

In a healthy person, insulin is released after consuming glucose, helping cells absorb sugar from the blood efficiently. If blood glucose remains high after two hours, it suggests:

• Insulin resistance (cells aren’t responding well to insulin)

• Impaired insulin production (pancreas isn’t making enough insulin)

• A combination of both

Some key points about type 2 diabetes:

1. Symptoms: These may include increased thirst, frequent urination, hunger, fatigue, blurred vision, slow-healing sores, or frequent infections. Some people with type 2 diabetes may not experience symptoms in the early stages of the disease.

2. Risk factors: These include being overweight, leading a sedentary lifestyle, having a family history of diabetes, being older, having a history of gestational diabetes, having polycystic ovary syndrome, or being of certain racial/ethnic groups (African Americans, Hispanic/Latino Americans, American Indians, and some Asian Americans and Pacific Islanders are at a higher risk).

3. Management: Type 2 diabetes can often be managed with healthy eating, regular exercise, and weight loss. Sometimes, oral medications or insulin injections are also needed.

4. Complications: If not managed well, type 2 diabetes can lead to various complications, such as heart disease, stroke, kidney disease, eye damage, nerve damage, and other problems.

How to read the results of an OGTT

For a 75g Oral Glucose Tolerance Test (OGTT) (the standard for diagnosing diabetes and prediabetes), the blood sugar levels are interpreted as follows:

Normal Results:

• Fasting (before the test): <100 mg/dL (5.6 mmol/L)

• 2 hours after drinking glucose: <140 mg/dL (7.8 mmol/L)

Prediabetes (Impaired Glucose Tolerance):

• 2-hour result: 140–199 mg/dL (7.8–11.0 mmol/L)

Diabetes Diagnosis:

• 2-hour result: ≥200 mg/dL (11.1 mmol/L)

Graph showing blood glucose responses over time for normal, prediabetes, and diabetes cases during an OGTT.

If your level falls in the normal range, your body is efficiently handling glucose. If they’re elevated, it could indicate insulin resistance or diabetes, and follow-up testing may be needed.

Do yourself a favor. The next time you are at your doctors or homeopathic doctor, order a OGTT.  You will be glad you did.

---

Want more science-backed insights on health and longevity? Subscribe now and get fresh, thought-provoking discussions delivered right to your inbox!