The American Diabetes Association (ADA) recommends that blood glucose screening for adults begin at age 45, or sooner if you are overweight and have additional risk factors for prediabetes or type 2 diabetes.
There are several blood tests for prediabetes.
Glycated hemoglobin (A1C) test
This test indicates your average blood sugar level for the past two to three months. Specifically, the test measures the percentage of blood sugar attached to the oxygen-carrying protein in red blood cells (hemoglobin). The higher your blood sugar levels, the more hemoglobin you'll have with sugar attached.
- An A1C level below 5.7 percent is considered normal
- An A1C level between 5.7 and 6.4 percent is considered prediabetes
- An A1C level of 6.5 percent or higher on two separate tests indicates type 2 diabetes
Certain conditions can make the A1C test inaccurate — such as if you are pregnant or have an uncommon form of hemoglobin (hemoglobin variant).
Fasting blood sugar test
A blood sample is taken after you fast for at least eight hours or overnight.
- A fasting blood sugar level below 100 milligrams per deciliter (mg/dL) — 5.6 millimoles per liter (mmol/L) — is considered normal.
- A fasting blood sugar level from 100 to 125 mg/dL (5.6 to 7.0 mmol/L) is considered prediabetes. This result is sometimes called impaired fasting glucose.
- A fasting blood sugar level of 126 mg/dL (7.0 mmol/L) or higher indicates type 2 diabetes.
Oral glucose tolerance test
This test is usually used to diagnose diabetes only during pregnancy. A blood sample is taken after you fast for at least eight hours or overnight. Then you'll drink a sugary solution, and your blood sugar level will be measured again after two hours.
- A blood sugar level less than 140 mg/dL (7.8 mmol/L) is considered normal.
- A blood sugar level from 140 to 199 mg/dL (7.8 to 11.0 mmol/L) is considered prediabetes. This is sometimes referred to as impaired glucose tolerance.
- A blood sugar level of 200 mg/dL (11.1 mmol/L) or higher indicates type 2 diabetes.
If you have prediabetes, further testing may be needed. At least once a year, your doctor will likely check your:
- Fasting blood sugar
- Hemoglobin A1C
- Total cholesterol, HDL, low-density lipoprotein (LDL), and triglycerides
Testing might occur more frequently if you have additional risk factors for diabetes.
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 at least two other risk factors for type 2 diabetes.
These other risk factors include:
- Family history of type 2 diabetes.
- Race. Children who are African-American, Hispanic or Native American are at higher risk.
- Sex and age. Type 2 diabetes is more common among girls than boys. A diagnosis of childhood type 2 diabetes often occurs during puberty — as early as age 10.
- Low birth weight.
- Being born to a mother who had gestational diabetes.
The ranges of blood sugar level considered normal, prediabetic and diabetic 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. Choose foods low in fat and calories and high in fiber. Focus on fruits, vegetables and whole grains. Strive for variety to help you achieve your goals without compromising taste or nutrition.
- Be more active. Aim for 30 to 60 minutes of moderate physical activity most days of the week.
- Lose excess weight. If you're overweight, losing just 5 to 10 percent of your body weight — only 10 to 20 pounds (4.5 to 9 kilograms) if you weigh 200 pounds (91 kilograms) — can reduce the risk of developing type 2 diabetes. To keep your weight in a healthy range, focus on permanent changes to your eating and exercise habits. Motivate yourself by remembering the benefits of losing weight, such as a healthier heart, more energy and improved self-esteem.
- Stop smoking.
- Take medications as needed. If you're at high risk of diabetes, your doctor might recommend metformin (Glucophage, others). Medications to control cholesterol and high blood pressure might also be prescribed.
Children and prediabetes treatment
Children with prediabetes should undertake the lifestyle changes recommended for adults with type 2 diabetes, including:
- Losing weight
- Eating fewer refined carbohydrates and fats, and more fiber
- Spending at least one hour every day in physical activity
Medication generally isn't recommended for children with prediabetes.
Explore Mayo Clinic studies testing new treatments, interventions and tests as a means to prevent, detect, treat or manage this disease.
Many alternative therapies have been touted as possible ways to treat or prevent type 2 diabetes, including:
- Cassia cinnamon
- White mulberry
Although some of these substances have shown promise in early trials, there's no definitive evidence that any of these alternative therapies are effective.
Talk to your doctor if you're considering dietary supplements or other alternative therapies to treat or prevent prediabetes. Some of these supplements or alternative therapies might be harmful if combined with certain prescription medications. Your doctor 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 doctor. He or she may refer you to a doctor who specializes in diabetes treatment (endocrinologist).
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'll probably need to fast for at least eight hours before your appointment so that your doctor 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 doctor.
For prediabetes, some basic questions to ask your doctor 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?
What to expect from your doctor
Your doctor 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?
Aug. 02, 2017