Introduction
Blood sugar tests measure how well your body processes sugar (glucose). Some blood sugar tests are used to diagnose prediabetes or diabetes. Others determine how well you're managing your diabetes.
Click on the tabs to the left to learn more about various blood sugar tests and what the results mean.
Fasting blood sugar test
What is a fasting blood sugar (glucose) test?
Measures the amount of sugar (glucose) in your blood after you fast for at least eight hours or overnight.
What's normal?
A normal range is 70 to 100 milligrams of glucose per deciliter of blood (mg/dL) or 3.9 to 5.6 millimoles per liter (mmol/L).
What level suggests prediabetes?
A level of 100 to 125 mg/dL (5.6 to 6.9 mmol/L) indicates impaired fasting glucose — commonly known as prediabetes. To confirm the diagnosis, your doctor may repeat the fasting blood sugar test several days to a week later.
What level suggests type 1 or type 2 diabetes?
In June 2009, an international committee composed of experts from the American Diabetes Association, the European Association for the Study of Diabetes and the International Diabetes Federation recommended that this test is no longer required to diagnose diabetes. However, it may be used if you're pregnant or have an uncommon form of hemoglobin (known as a hemoglobin variant). In such cases, a level of 126 mg/dL (7 mmol/L) or higher is consistent with either type 1 or type 2 diabetes. To confirm the diagnosis, your doctor may repeat the fasting blood sugar test on another day. If your test results are 126 mg/dL (7 mmol/L) or higher twice in a row after at least eight hours of fasting, you may have diabetes. Further testing may be needed to determine whether you have type 1 diabetes or type 2 diabetes.
Random blood sugar test
What is a random blood sugar test?
Measures your blood sugar at any point in time, not necessarily a certain amount of time after a meal, snack or beverage.
What's normal?
A normal random blood sugar level hasn't been clearly defined. However, even if you've recently eaten and your blood sugar level is at its peak, your random blood sugar level shouldn't be higher than 200 mg/dL (11.1 mmol/L).
What level suggests prediabetes?
Although no clear criteria have been established, a level higher than 140 mg/dL (7.8 mmol/L) but lower than 200 mg/dL (11.1 mmol/L), may indicate prediabetes. Your doctor may recommend additional testing.
What level suggests type 1 or type 2 diabetes?
A level higher than 200 mg/dL (11.1 mmol/L) suggests either type 1 or type 2 diabetes. Remember, your blood sugar level alone isn't enough to differentiate between type 1 and type 2 diabetes. Your doctor may do other tests to determine which type of diabetes you have.
Oral glucose tolerance test
What is an oral glucose tolerance test?
An oral glucose tolerance test measures your body's response to sugar. First your fasting blood sugar level is measured. Then you drink a sugary solution. Your blood sugar level is measured after one hour and again after two hours. If your blood sugar level rises more than expected — to 200 mg/dL (11.1 mmol/L) or more — you may have diabetes. A modified version of the oral glucose tolerance test, known as a glucose challenge test, is often used to screen pregnant women for gestational diabetes.
What's normal?
A normal blood sugar level after an oral glucose tolerance test is lower than 140 mg/dL (7.8 mmol/L).
What level suggests prediabetes?
If your blood sugar level is 140 to 199 mg/dL (7.8 to 11.0 mmol/L) after an oral glucose tolerance test, you may have prediabetes.
What level suggests type 1 or type 2 diabetes?
A blood sugar level of 200 mg/dL (11.1 mmol/L) or higher two hours after you drink the sugary solution may indicate diabetes. Your doctor may repeat this or other tests to confirm the diagnosis. Further testing may be needed to determine whether you have type 1 diabetes or type 2 diabetes.
Glycated hemoglobin (A1C) test
What is an A1C test?
This test can be used to diagnose diabetes and also gauge how well you're managing your diabetes.
The A1C test reflects your average blood sugar level for the past two to three months. Test results show what percentage of your hemoglobin — a protein found in red blood cells — is sugar coated (glycated).
What's normal?
The normal range for people without diabetes is 4 to 6 percent, although normal ranges may vary among laboratories.
What level suggests prediabetes?
When used diagnostically, a level of 6 to 6.5 percent suggests prediabetes.
What level suggests type 1 or type 2 diabetes?
When used diagnostically, a level of 6.5 percent or higher on two separate tests suggests diabetes. Further testing may be needed to determine whether you have type 1 diabetes or type 2 diabetes.
What level is desired in people with diabetes?
Your target A1C goal may vary depending on your age and various other factors, but the American Diabetes Association generally recommends that A1C levels be below 7 percent. Discuss what level is appropriate for you with your doctor.
