Did you know that diabetes affects more than 38 million people in the United States? In fact, diabetes often develops slowly, with symptoms so mild they’re easy to miss. That’s why knowing how to test for diabetes is very important.

This article explains the most common ways diabetes is diagnosed, who should be screened and when, how results are confirmed, and what happens after a diagnosis.

If you’re experiencing symptoms or have risk factors, understanding your diagnosis of diabetes can help you take the next step toward managing your health.

What Is the Diagnosis of Diabetes?

Diabetes is diagnosed when someone has hyperglycemia, which means their blood sugar is too high for too long. This can happen when the body doesn’t make enough insulin or can’t use it the right way. Some people find out they have diabetes after feeling sick, while others are diagnosed during a regular checkup — even if they feel fine.

Diabetes often develops slowly, with symptoms so mild they’re easy to miss.

Doctors look at your symptoms, medical history, and whether you are at high risk because of factors like age, weight, or family history of diabetes. Once diabetes is diagnosed, your doctor will talk with you about the types of diabetes (like type 1 diabetes, type 2 or diabetes mellitus, or gestational diabetes) and the best way to manage it.

Getting the right diabetes care early on can help you stay healthy, feel better, and avoid serious problems later.

Who Should Be Tested for Type 2 Diabetes?

Type 2 diabetes is most commonly diagnosed in people aged 45 or older, but younger adults and even children can develop type 2 diabetes too. Diabetes screening is recommended for people who:

• Are 35 or older
• Have a body mass index (BMI) over 25 — or over 23 for Asian Americans — and have other factors linked to a higher risk of diabetes, such as high blood pressure, unhealthy cholesterol levels, a sedentary lifestyle, polycystic ovary syndrome, heart disease, or a close family member with diabetes
• Have been diagnosed with prediabetes — a condition where blood sugar levels are higher than normal but not high enough to be considered diabetes
• Had gestational diabetes while pregnant

Most people are diagnosed with diabetes by their primary care physician or family doctor. Your general practitioner may continue to treat your diabetes, or they may refer you to an endocrinologist. Endocrinologists specialize in diseases of the glands and hormone imbalance — diabetes involves problems with the pancreas, a gland that produces the hormone insulin.

What Are the 3 Most Common Symptoms of Undiagnosed Diabetes?

Many people with undiagnosed type 2 diabetes don’t notice symptoms until their blood sugar is very high. Three signs are especially common:

1. Frequent urination — High blood sugar causes excess glucose to spill into the urine, leading to frequent trips to the bathroom, especially at night.
2. Excessive thirst — As the body loses fluid through urination, it triggers constant thirst that doesn’t improve with drinking water.
3. Unexplained weight loss — Without enough insulin and high blood sugar levels, the body breaks down fat and muscle for energy, causing sudden weight loss.

Other possible signs of undiagnosed diabetes include blurry vision, fatigue, slow-healing wounds, and frequent infections. If you notice any of these signs — or if you have risk factors for diabetes — talk to your doctor about getting tested. Catching the condition early gives you the best chance to manage it effectively and avoid serious diabetes complications.

How Is Type 2 Diabetes Diagnosed?

Your doctor will draw a small blood sample to test your blood glucose level. In people with type 2 diabetes, cells become resistant to insulin. Insulin is the hormone necessary to allow cells to take in glucose from the bloodstream and regulate how much glucose remains in your blood. As diabetes progresses, cells can take in less and less glucose, and blood glucose levels rise.

Catching the condition early gives you the best chance to manage it effectively and avoid serious diabetes complications.

There are several ways of testing blood glucose. The doctor will likely repeat the blood test on another day soon after to make sure the diagnosis is correct.

A1c Test

The A1c test — also called hemoglobin A1C, HbA1c, or glycated hemoglobin — shows your average blood sugar level over the past two to three months. According to the American Diabetes Association, the A1c test is used to diagnose type 2 diabetes and to check how well blood sugar is being controlled in people who are getting treatment. Here are the values to look at:

• Less than 5.7 percent — Considered normal
• 5.7 percent to 6.4 percent — Indicates prediabetes
• 6.5 percent or higher — Indicates diabetes

Oral Glucose Tolerance Test

For the oral glucose tolerance test (OGTT), you first have a blood sample taken after not eating for at least eight hours. Then, you drink a sweet liquid with a lot of sugar. Two hours later, another blood sample is taken to see how your body handles the sugar.

The results are measured in milligrams per deciliter, often abbreviated as mg/dL. Here’s what the results mean:

• Less than 140 milligrams per deciliter — Considered normal
• 140 to 199 milligrams per deciliter — May indicate prediabetes
• 200 milligrams per deciliter or higher — Indicates diabetes

Fasting Plasma Glucose

A fasting plasma glucose (FPG) test, also called a fasting blood sugar test, is usually done in the morning. You’ll need to fast — that means no food or drinks except water — for at least eight hours before your blood is taken.

FPG results are measured in milligrams per deciliter. Here’s what they mean:

• Less than 100 milligrams per deciliter — Considered normal
• 100 to 125 milligrams per deciliter — Indicates prediabetes
• 126 milligrams per deciliter or higher — Indicates diabetes

Random Plasma Glucose Test

A blood sample for a random or casual blood glucose test can be taken at any time. Results are expressed in milligrams per deciliter. A test result of 200 milligrams per deciliter or higher indicates diabetes. Any test would need to be repeated to confirm the diagnosis of type 2 diabetes.

Speak With Your Doctor

If you think you may be at risk of diabetes, speak with your healthcare provider. They can recommend a screening test to evaluate your diabetes risk and determine whether further testing or a follow-up appointment is needed. If you’re diagnosed, your doctor can help create a treatment plan that may include lifestyle changes to manage your blood sugar and reduce the chance of diabetes complications.

Whether you’re navigating a new diagnosis yourself or supporting a loved one, remember that managing diabetes isn’t just about numbers — it takes a whole-person, multifactorial approach. Compassionate diabetes care includes medical treatment, emotional support, self-care, physical activity, and practical guidance for everyday life. You deserve a care plan that meets your unique needs and helps you feel empowered, not overwhelmed.

Find Your Team

DiabetesTeam is the social network for people with diabetes and their loved ones. On DiabetesTeam, members come together to ask questions, give advice, and share their stories with others who understand life with diabetes.

Do you remember how you were first diagnosed with diabetes? Were you surprised by the results of your blood tests or experiencing symptoms before getting tested? Share your thoughts in the comments below, or start a conversation by posting on your Activities page.