The most reliable way to know if you’re diabetic is a blood test, but your body often sends warning signs first. Some people notice increased thirst, frequent urination, and unexplained fatigue for weeks or months before getting a diagnosis. Others have no symptoms at all, especially in the early stages of type 2 diabetes. Understanding what to look for, both in how you feel and what shows up on lab work, can help you catch it early.
Symptoms That Show Up First
Diabetes disrupts how your body uses sugar for energy. When blood sugar stays elevated, three classic symptoms tend to emerge together. Frequent urination happens because your kidneys work overtime to flush excess sugar from the blood. That fluid loss triggers intense thirst, which leads to drinking far more than usual. And because your cells aren’t absorbing sugar properly, you feel hungrier than normal as your body tries to compensate for the energy it’s losing.
Beyond those three, other common signs include extreme fatigue, blurry vision, slow healing of cuts or bruises, and tingling, pain, or numbness in your hands or feet. Not everyone experiences all of these, and some people have none. That’s why screening matters even when you feel fine.
Type 1 and Type 2 Feel Different
Type 1 diabetes symptoms develop fast, usually over days to weeks. The immune system destroys the cells that produce insulin, so blood sugar rises sharply. Rapid, unexplained weight loss is a hallmark of type 1, even when appetite increases. Children with type 1 often eat more but keep losing weight. This form is most commonly diagnosed in children and young adults, though it can appear at any age.
Type 2 diabetes is far more gradual. Symptoms can develop over several years, and many people live with elevated blood sugar for a long time without realizing it. Because the onset is slow, type 2 is frequently caught during routine bloodwork rather than from obvious symptoms. That slow progression also means more damage can accumulate before diagnosis, particularly to nerves, kidneys, and blood vessels.
Skin Changes You Might Notice
Your skin can reveal insulin problems before a blood test does. One of the most recognizable signs is dark, velvety patches of skin that appear in body creases like the neck, armpits, or groin. This condition, called acanthosis nigricans, signals insulin resistance and can be an early marker of prediabetes or type 2 diabetes. It sometimes also appears on the hands, elbows, or knees.
Other skin changes linked to diabetes include red or brown round patches on the shins, dry and persistently itchy skin from poor circulation, and recurring bacterial or fungal infections in warm, moist skin folds. If you’re noticing skin issues alongside any of the symptoms above, that combination is worth mentioning to your doctor.
What the Blood Tests Actually Measure
Three main tests are used to diagnose diabetes. Each measures blood sugar in a different way, and any one of them can confirm a diagnosis.
- A1C test: This reflects your average blood sugar over the past two to three months. A result below 5.7% is normal. Between 5.7% and 6.4% is prediabetes. At 6.5% or higher, you’re in the diabetes range. No fasting is required.
- Fasting blood glucose: You fast overnight, then have your blood drawn in the morning. Normal is below 100 mg/dL. Between 100 and 125 mg/dL is prediabetes. At 126 mg/dL or higher, it indicates diabetes.
- Oral glucose tolerance test: After fasting, you drink a solution containing 75 grams of sugar. Your blood is drawn two hours later. A reading of 200 mg/dL or higher suggests diabetes, while 140 to 199 mg/dL falls in the prediabetes range.
Doctors typically confirm a diabetes diagnosis by repeating the test or running a second type of test, unless symptoms are already obvious and blood sugar is very high.
Prediabetes: The In-Between Stage
Prediabetes means your blood sugar is elevated but not yet high enough for a diabetes diagnosis. It’s defined by an A1C of 5.7% to 6.4%, a fasting glucose of 100 to 125 mg/dL, or a two-hour glucose tolerance result of 140 to 199 mg/dL. This stage is extremely common and often produces no symptoms at all.
The reason prediabetes matters is that it’s reversible. Modest weight loss (even 5% to 7% of body weight), regular physical activity, and dietary changes can bring blood sugar back to normal levels and significantly reduce the risk of progressing to type 2 diabetes. Without intervention, most people with prediabetes will develop type 2 within 10 years.
Who Should Get Screened
The U.S. Preventive Services Task Force recommends screening for prediabetes and type 2 diabetes in adults aged 35 to 70 who are overweight or obese (a BMI of 25 or higher). If you’re Asian American, screening is recommended at a BMI of 23 or higher, because the risk threshold is lower. Earlier screening is also recommended for people who are American Indian, Alaska Native, Black, Hispanic or Latino, or Native Hawaiian or Pacific Islander, since these groups face disproportionately higher rates of diabetes.
Outside of those guidelines, you should consider getting tested if you have a family history of diabetes, have had gestational diabetes during pregnancy, or have polycystic ovary syndrome. Any of the symptoms described earlier, regardless of your age or weight, also warrant testing.
Can You Test at Home?
Over-the-counter A1C kits are available at most pharmacies, but their accuracy is limited. A University of Florida Health study tested three popular home A1C kits against standard lab results. The benchmark for accuracy is that home results should fall within 5% of lab values at least 90% of the time. The best-performing kit met that standard in only 82% of samples. The other two hit it in just 46% and 29% of samples.
A home kit might give you a rough sense of where you stand, but a result in the normal range doesn’t rule out diabetes, and an elevated result needs lab confirmation. If you’re concerned enough to buy a home test, you’re better off scheduling a blood draw with your doctor, where the results will be definitive.
Emergency Warning Signs
In some cases, diabetes announces itself with a dangerous complication called diabetic ketoacidosis, or DKA. This happens when the body can’t use sugar for fuel and starts breaking down fat at a dangerous rate, producing acidic compounds called ketones. DKA is most common in type 1 diabetes but can occur in type 2 as well.
Early signs include extreme thirst and urinating far more than usual. If untreated, symptoms escalate quickly to fast, deep breathing, nausea and vomiting, stomach pain, a flushed face, and breath that smells fruity or sweet. If your breath smells fruity, you’re vomiting and can’t keep anything down, you’re having trouble breathing, or a glucose reading shows 300 mg/dL or above, that’s an emergency requiring immediate medical attention.