The American Diabetes Association (ADA) recommends that diabetes screening for most adults begin at age 45. The ADA advises diabetes screening before age 45 if you're overweight and have additional risk factors for prediabetes or type 2 diabetes.
If you've had gestational diabetes, your health care provider will likely check your blood sugar levels at least once every three years.
There are several blood tests for prediabetes.
Glycated hemoglobin (A1C) test
This test indicates your average blood sugar level for the past 2 to 3 months.
- Below 5.7% is normal
- Between 5.7% and 6.4% is diagnosed as prediabetes
- 6.5% or higher on two separate tests indicates diabetes
Certain conditions can make the A1C test inaccurate — such as if you're pregnant or have an uncommon form of hemoglobin.
Fasting blood sugar test
A blood sample is taken after you haven't eaten for at least eight hours or overnight (fast).
Blood sugar values are expressed in milligrams of sugar per deciliter (mg/dL) or millimoles of sugar per liter (mmol/L) of blood. In general:
- Less than 100 mg/dL (5.6 mmol/L) is normal
- 100 to 125 mg/dL (5.6 to 6.9 mmol/L) is diagnosed as prediabetes
- 126 mg/dL (7.0 mmol/L) or higher on two separate tests is diagnosed as diabetes
Oral glucose tolerance test
This test is less commonly used than the others, except during pregnancy. You'll need to fast overnight and then drink a sugary liquid at the primary care provider's office or lab testing site. Blood sugar levels are tested periodically for the next two hours.
- Less than 140 mg/dL (7.8 mmol/L) is normal
- 140 to 199 mg/dL (7.8 to 11.0 mmol/L) is consistent with prediabetes
- 200 mg/dL (11.1 mmol/L) or higher after two hours suggests diabetes
If you have prediabetes, your health care provider will typically check your blood sugar levels at least once a year.
Children and prediabetes testing
Type 2 diabetes is becoming more common in children and adolescents, likely due to the rise in childhood obesity.
The ADA recommends prediabetes testing for children who are overweight or obese and who have one or more other risk factors for type 2 diabetes, such as:
- Family history of type 2 diabetes
- Being of a race or ethnicity associated with an increased risk
- Low birth weight
- Being born to a mother who had gestational diabetes
The ranges of blood sugar level considered normal, prediabetes and diabetes are the same for children and adults.
Children who have prediabetes should be tested annually for type 2 diabetes — or more often if the child experiences a change in weight or develops signs or symptoms of diabetes, such as increased thirst, increased urination, fatigue or blurred vision.
Healthy lifestyle choices can help you bring your blood sugar level back to normal, or at least keep it from rising toward the levels seen in type 2 diabetes.
To prevent prediabetes from progressing to type 2 diabetes, try to:
- Eat healthy foods. A diet high in fruits, vegetables, nuts, whole grains and olive oil is associated with a lower risk of prediabetes. Choose foods low in fat and calories and high in fiber. Eat a variety of foods to help you achieve your goals without compromising taste or nutrition.
- Be more active. Physical activity helps you control your weight, uses up sugar for energy and helps the body use insulin more effectively. Aim for at least 150 minutes of moderate or 75 minutes of vigorous aerobic activity a week, or a combination of moderate and vigorous exercise.
- Lose excess weight. If you're overweight, losing just 5% to 7% of your body weight — about 14 pounds (6.4 kilograms) if you weigh 200 pounds (91 kilograms) — can significantly reduce the risk of type 2 diabetes. To keep your weight in a healthy range, focus on permanent changes to your eating and exercise habits.
- Stop smoking. Stopping smoking can improve the way insulin works, improving your blood sugar level.
- Take medications as needed. If you're at high risk of diabetes, your health care provider might recommend metformin (Glumetza). Medications to control cholesterol and high blood pressure might also be prescribed.
Children and prediabetes treatment
Children with prediabetes should follow the lifestyle changes recommended for adults with type 2 diabetes, including:
- Losing weight
- Eating fewer refined carbohydrates and fats, and more fiber
- Reducing portion sizes
- Eating out less often
- Spending at least one hour every day in physical activity
Medication generally isn't recommended for children with prediabetes unless lifestyle changes aren't improving blood sugar levels. If medication is needed, metformin is usually the recommended drug.
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Explore Mayo Clinic studies testing new treatments, interventions and tests as a means to prevent, detect, treat or manage this condition.
Many alternative therapies have been touted as possible ways to treat or prevent type 2 diabetes. But there's no definitive evidence that any alternative treatments are effective. Therapies that have been said to be helpful in type 2 diabetes and are also likely to be safe, include:
- Cassia cinnamon
- Xanthan gum
Talk to your health care provider if you're considering dietary supplements or other alternative therapies to treat or prevent prediabetes. Some supplements or alternative therapies might be harmful if combined with certain prescription medications. Your health care provider can help you weigh the pros and cons of specific alternative therapies.
Preparing for your appointment
You're likely to start by seeing your primary care provider. He or she may refer you to a specialist in diabetes treatment (endocrinologist), a dietitian or a certified diabetes educator.
Here's some information to help you get ready for your appointment.
What you can do
Before your appointment, take these steps:
- Ask about any pre-appointment restrictions. You may need to fast for at least eight hours before your appointment so that your health care provider can measure your fasting blood sugar level.
- List symptoms you've been having and for how long.
- List all medications, vitamins and supplements you take, including the doses.
- List key personal and medical information, including other conditions, recent life changes and stressors.
- Prepare questions to ask your health care provider.
Some basic questions to ask include:
- How can I prevent prediabetes from turning into type 2 diabetes?
- Do I need to take medication? If so, what side effects can I expect?
- I have other health conditions. How can I best manage them together?
- How much do I need to exercise each week?
- Should I avoid any foods? Can I still eat sugar?
- Do I need to see a dietitian?
- Can you recommend any local programs for preventing diabetes?
What to expect from your doctor
Your health care provider is likely to ask you a number of questions, such as:
- Has your weight changed recently?
- Do you exercise regularly? If so, for how long and how often?
- Do you have a family history of diabetes?