The only way to confirm whether you have diabetes is through a blood test ordered by a doctor. But there are warning signs you can watch for at home, and understanding the testing process can help you take the right next step quickly. Most people with type 2 diabetes have no obvious symptoms in the early stages, which is why routine screening matters even when you feel fine.
Symptoms That May Signal Diabetes
When blood sugar stays elevated, your body gives off several signals. The most common are increased urination, unusual thirst, and persistent hunger even after eating. These happen because your cells can’t absorb glucose from the blood without enough insulin working properly. The glucose builds up in your bloodstream instead of fueling your cells, so your body tries to flush the excess sugar through urine. That fluid loss triggers thirst, and your energy-starved cells send hunger signals to your brain.
Other symptoms include blurry vision, slow-healing cuts or bruises, tingling or numbness in your hands and feet, unexplained weight loss, and fatigue that doesn’t improve with rest. Frequent yeast infections or urinary tract infections can also be a sign, particularly in women.
How fast symptoms appear depends on the type. Type 1 diabetes symptoms can show up suddenly, especially in children, sometimes over just a few weeks. Type 2 diabetes develops gradually over months or years, and many people don’t notice anything until complications start. That slow onset is exactly why blood testing is so important.
Who Should Get Tested
Both the U.S. Preventive Services Task Force and the American Diabetes Association now recommend screening for prediabetes and type 2 diabetes starting at age 35, with repeat testing every three years. The ADA also recommends that adults of any age with overweight or obesity and at least one additional risk factor get tested. Those risk factors include a family history of diabetes, physical inactivity, a history of gestational diabetes, or belonging to a racial or ethnic group with higher rates of diabetes (including Black, Hispanic, Native American, Asian American, and Pacific Islander communities).
If you’re pregnant, screening for gestational diabetes is recommended at 24 weeks of gestation or after. This is a separate condition that develops during pregnancy, and most providers test for it as part of routine prenatal care between weeks 24 and 28.
The Three Main Blood Tests
Doctors use three tests to diagnose diabetes, and any one of them can provide a diagnosis. Your provider will choose based on your situation, though an abnormal result is typically confirmed with a second test on a different day.
A1C Test
This measures your average blood sugar over the past two to three months. It doesn’t require fasting, so it can be done at any time of day. The results break down like this:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
Fasting Blood Sugar Test
This measures your blood glucose after you haven’t eaten for 8 to 12 hours. You can drink plain water during the fast, but coffee, juice, soda, and flavored water are off limits because they can affect results. You should also avoid chewing gum, smoking, and exercise during the fasting period. Most people schedule this first thing in the morning to make the overnight fast easier.
- Normal: 99 mg/dL or below
- Prediabetes: 100 to 125 mg/dL
- Diabetes: 126 mg/dL or higher
Glucose Tolerance Test
This test also requires fasting. Your blood is drawn, then you drink a sugary liquid, and your blood is drawn again two hours later to see how well your body processes the sugar. It takes longer than the other tests but gives a clear picture of how your body handles glucose in real time.
- Normal: 140 mg/dL or below (at 2 hours)
- Prediabetes: 140 to 199 mg/dL
- Diabetes: 200 mg/dL or higher
What About Home Testing?
You can buy blood glucose monitors and even A1C kits at a pharmacy. These are useful for spotting a potential problem or for daily monitoring if you already have diabetes, but they aren’t considered reliable enough for a formal diagnosis. Home devices have wider margins of error than laboratory equipment, and a single fingerstick reading can vary depending on when you ate, your hydration, and even the temperature of the test strip. If a home test shows a high reading, treat it as a reason to get lab work done, not as a diagnosis on its own.
Understanding a Prediabetes Result
About one in three American adults has prediabetes, and most of them don’t know it. If your results land in the prediabetes range on any of the three tests, it means your blood sugar is elevated but not yet high enough for a diabetes diagnosis. This is a critical window. Losing 5% to 7% of your body weight through dietary changes and regular physical activity can significantly lower the risk of progressing to type 2 diabetes. Prediabetes is not a guarantee that you’ll develop diabetes. It’s more like an early warning system your body is giving you while the situation is still reversible.
What Happens After a Diagnosis
If your blood tests confirm diabetes, the next steps depend on the type. Type 2 diabetes, which accounts for roughly 90% to 95% of cases, is often managed initially with lifestyle changes and oral medication. Your doctor will set a target A1C level for you (usually below 7%) and schedule follow-up blood work every few months to track your progress.
Type 1 diabetes requires insulin from the start because the body’s immune system has attacked the cells that produce it. This type is usually diagnosed in children and young adults, though it can appear at any age. If your doctor suspects type 1, additional blood tests for specific antibodies can confirm it.
For gestational diabetes, management focuses on blood sugar monitoring, dietary adjustments, and sometimes insulin during the remainder of pregnancy. Blood sugar typically returns to normal after delivery, but having gestational diabetes raises your risk of developing type 2 diabetes later in life, so follow-up testing after pregnancy is recommended.