Understanding glucose tolerance test results

Overview

A glucose tolerance test (GTT) checks how well your body processes sugar (glucose). The results can show if your blood sugar is normal, slightly high (impaired glucose tolerance or pre-diabetes), or high enough to be diabetes.

Abnormal glucose tolerance is common. Many adults have pre-diabetes, and millions have diabetes. The test helps catch problems early.

Anyone can have abnormal glucose tolerance, but it is more common in people who are overweight, have a family history of diabetes, are over 45, or have certain ethnic backgrounds.

Symptoms

Common symptoms

• Often there are no symptoms with early abnormal glucose tolerance.
• Increased thirst and urination
• Unexplained weight loss
• Fatigue
• Blurred vision

Symptoms in children

• Increased thirst and frequent urination
• Bedwetting in a child who previously was dry at night
• Weight loss despite increased appetite
• Irritability or mood changes
• Yeast infections in girls

Symptoms in older adults

• Confusion or dizziness
• Frequent infections
• Slow healing of cuts or sores
• Numbness or tingling in hands or feet

Causes

Main causes

• Abnormal glucose tolerance is caused by insulin resistance (cells not responding well to insulin) or the pancreas not making enough insulin.
• It can be temporary, such as during pregnancy (gestational diabetes).

Risk factors

• Being overweight or obese
• Physical inactivity
• Family history of diabetes
• Age over 45
• Having high blood pressure or high cholesterol
• Certain ethnicities (South Asian, African-Caribbean, Hispanic)
• History of gestational diabetes or polycystic ovary syndrome (PCOS)

When to see a doctor

See a doctor urgently if:

• If you experience symptoms of very high or low blood sugar (see emergency section)
• If you are pregnant and have symptoms of gestational diabetes

Book a routine appointment if:

• If you have risk factors for diabetes, talk to your doctor about getting tested.
• If you are over 40, consider routine screening as part of a health check.

Diagnosis

A glucose tolerance test is one way to diagnose diabetes or pre-diabetes. Your doctor will interpret the results along with other tests.

Tests that may be done

• Oral glucose tolerance test (OGTT): a fasting blood sugar, then drinking a glucose drink, and blood tests at 1 and 2 hours.
• Fasting blood sugar test
• HbA1c test (average blood sugar over 3 months)

What to expect at your appointment

You will need to fast for 8-12 hours before the test. A needle is placed in your arm to draw blood. After the glucose drink, you must wait in the clinic and have more blood draws. The test takes about 2-3 hours. You should not eat or drink anything except water during the test.

Treatment

Treatment depends on whether you have pre-diabetes or diabetes. It focuses on controlling blood sugar to prevent complications.

Self-care at home

• Follow a healthy eating plan that is low in refined sugars and high in fibre.
• Get regular physical activity, such as walking for 30 minutes most days.
• Monitor your blood sugar at home as advised by your healthcare team.
• Keep a healthy weight.
• Manage stress levels.

Medical treatments

Your doctor may prescribe medications to help control blood sugar. These can include tablets or injectable medicines. Never stop or change medications without speaking to your doctor. Insulin injections may be needed for some types of diabetes.

When is surgery considered?

Surgery is not a standard treatment for abnormal glucose tolerance. In some cases, weight loss surgery (bariatric surgery) may be considered for people with obesity and type 2 diabetes, but it is not the first option.

Living with this condition

Living with abnormal glucose tolerance involves checking your blood sugar regularly, taking any prescribed medications, and making healthy choices. You can still lead a full, active life.

Lifestyle tips

• Eat at regular times and avoid skipping meals.
• Choose water instead of sugary drinks.
• Include protein and healthy fats in meals to keep blood sugar stable.
• Get 7-9 hours of sleep each night.

Diet and exercise

A diet rich in vegetables, whole grains, lean proteins, and healthy fats helps manage blood sugar. Exercise helps your body use insulin better. Aim for 150 minutes of moderate activity per week, like brisk walking or cycling.

Mental health and emotional wellbeing

A diagnosis of pre-diabetes or diabetes can be stressful and may lead to anxiety or depression. It is important to talk to your healthcare provider about how you are feeling. If you need urgent help, contact a crisis support line.

Prevention

For many people, type 2 diabetes and pre-diabetes can be prevented or delayed with healthy lifestyle changes, such as losing weight, eating well, and exercising.

Screening programmes

If you have risk factors, your doctor may recommend screening tests like a glucose tolerance test or HbA1c every 1-3 years.

Complications

If left untreated

• High blood sugar can damage blood vessels and nerves over time.
• Increased risk of heart disease, stroke, and kidney disease.
• Eye problems, including vision loss.
• Nerve damage leading to numbness, pain, or infections in feet.
• Slow healing and increased risk of infections.

Long-term outlook

With early detection and proper management, most people with abnormal glucose tolerance can prevent or delay complications and live long, healthy lives. The key is to work with your healthcare team and stay committed to healthy habits.

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