If you experience excessive thirst, frequent urination, fatigue, weight loss, or blurred vision—symptoms of diabetes—then your doctor may want to do bloodwork to determine if you have prediabetes.

Prediabetes is a condition in which your blood sugar is higher than normal, but not high enough to be considered type 2 diabetes. If you catch prediabetes early, there are steps you can take to help prevent it from developing into type 2 diabetes. Preventive measures include losing weight, exercising daily, and eating nutritious meals low in sugar and starchy carbs.

Here are the three most common blood tests used to diagnose prediabetes and diabetes:

HbA1c

What it is: This test, often called A1c for short, shows your average blood sugar level for the past two or three months. Specifically, the HbA1c test measures what percentage of your hemoglobin—a protein in red blood cells that carries oxygen—is coated with sugar, according to Mayo Clinic.

Why it’s used: Many diabetes experts recommend that the A1c test be the primary test used to diagnose prediabetes. Because it measures your average blood sugar levels over time instead of at a specific point in time, it is a better overall reflection of your blood sugar levels.

What it means: The test report gives the results as a percentage. The higher the percentage, the higher your blood sugar level. A normal A1c result is below 5.7 percent. An A1c level between 5.7 percent and 6.4 percent means you may have prediabetes.

Fasting plasma glucose test

What it is: This blood test measures glucose levels after you have fasted for at least eight hours.

Why it’s used: Fasting stimulates hormones in the body that raise plasma glucose levels. In people without diabetes, the body will make enough insulin to counteract the rise in glucose levels. In people with diabetes, however, this does not happen, and the tested glucose levels will remain high.

What it means: Normal fasting blood glucose is between 70 and 100 milligrams per deciliter for people who do not have diabetes, according to WebMD. A result of 100 to 125 milligrams per deciliter may indicate the presence of prediabetes.

Oral glucose tolerance test

What it is: This test is used in conjunction with the fasting plasma glucose test to gather additional information about your blood sugars. You will be asked to drink a sweet liquid containing a measured amount of glucose (a type of sugar), usually between 50 to 100 grams. With the fasting plasma glucose test acting as a baseline, your blood glucose levels will then be measured again at one-hour intervals after you drink the liquid.

Why it’s used: This test lets your doctor see how your body uses the glucose you consume. The test is primarily used to diagnose gestational diabetes, but it can help in determining prediabetes if you are showing symptoms.

What it means: Two hours after consuming 75 grams of glucose, if your test results show a blood sugar level between 140 and 199 milligrams per deciliter, you may have prediabetes.

Do not try to diagnose yourself if you think you might have diabetes or prediabetes, the National Institute of Diabetes and Digestive and Kidney Diseases advises. Testing equipment that you can buy over the counter, such as a blood glucose meter, cannot diagnose diabetes, they note.

It’s also important to know that some people will not have any symptoms but may have risk factors for diabetes, such as obesity or a family history of the disease. If this is the case for you, it’s a good idea to get tested for prediabetes as well.

Did a blood test determine you had prediabetes? Share your thoughts and experiences with diabetes tests and screenings by commenting below.