The most reliable way to know if you have diabetes is a blood test, but your body often sends warning signs first. Increased thirst, frequent urination, unexplained fatigue, and blurry vision are the hallmark symptoms. Some people, especially those developing type 2 diabetes, experience these so gradually that they dismiss them for years. Others, particularly with type 1 diabetes, feel symptoms hit hard over just days or weeks.
The Core Symptoms to Watch For
When blood sugar stays elevated, your kidneys work overtime trying to filter and absorb the excess. Eventually they can’t keep up, and sugar spills into your urine, pulling fluid from your tissues along with it. This single chain reaction explains the three symptoms that overlap in nearly every case: you urinate more than usual, you feel dehydrated and thirsty, and you feel exhausted because your body can’t efficiently convert sugar into energy.
Beyond that triad, there are several other common signs:
- Unexplained weight loss. When sugar leaves through urine, those calories go with it. Combined with dehydration, this can cause rapid, unintentional weight loss, particularly in type 1 diabetes.
- Blurry vision. High blood sugar pulls fluid from the lenses of your eyes, temporarily warping your ability to focus.
- Slow-healing cuts or sores. Elevated sugar impairs blood flow and disrupts your body’s natural repair process. Foot wounds are especially slow to heal.
- Tingling or numbness in your hands and feet. Sustained high blood sugar damages nerves. You may also feel burning pain in your arms, hands, legs, or feet.
- Frequent infections. Women with diabetes are more prone to bladder and vaginal yeast infections. Gum infections and swollen, tender gums are also common because diabetes weakens your ability to fight bacteria.
Type 1 vs. Type 2: How Fast Symptoms Appear
Type 1 diabetes symptoms usually develop quickly, over a few days to weeks. Because the immune system is destroying the cells that make insulin, blood sugar rises fast and the signs are hard to ignore. This form is most often diagnosed in children and young adults, though it can appear at any age.
Type 2 diabetes is the opposite. Symptoms develop slowly, sometimes over several years. Blood sugar creeps up gradually, and your body partially compensates, so you might attribute the fatigue or extra bathroom trips to aging, stress, or not sleeping well. Many people with type 2 diabetes have no obvious symptoms at all and only find out through routine blood work. That’s why screening matters even when you feel fine.
Physical Signs You Can See
Certain skin changes can signal diabetes or the insulin resistance that precedes it. The most well-known is dark, velvety patches of skin that appear in body creases: the neck, armpits, or groin. This condition is a direct sign of insulin resistance and can appear before a diabetes diagnosis, making it one of the earliest visible clues that something is off.
Other skin changes linked to diabetes include light brown or reddish round spots on the shins (sometimes called shin spots), dry and persistently itchy skin from poor circulation, and frequent bacterial or fungal infections like recurring athlete’s foot, jock itch, or styes on the eyelids. Thick, tight, waxy skin on the fingers that limits joint movement is another sign, though less common. None of these skin changes on their own confirm diabetes, but combined with other symptoms, they’re worth mentioning to a doctor.
When It Becomes an Emergency
If type 1 diabetes goes undiagnosed or insulin levels drop dangerously low, the body starts burning fat for fuel and produces acids called ketones. This is diabetic ketoacidosis, and it can become life-threatening quickly. Get to an emergency room if you notice any combination of the following: breath that smells fruity or sweet, vomiting that won’t stop, difficulty breathing, or a blood sugar reading of 300 mg/dL or above. Ketoacidosis is most common in type 1 diabetes but can occasionally occur in type 2 as well.
Who Should Get Screened
Current guidelines from both the American Diabetes Association and the U.S. Preventive Services Task Force recommend screening starting at age 35 for adults who are overweight or obese, with repeat testing every three years. The ADA also recommends screening for any adult with overweight or obesity who has at least one additional risk factor, such as a family history of diabetes, a sedentary lifestyle, a history of gestational diabetes, or belonging to a racial or ethnic group with higher diabetes rates (including Black, Hispanic, Native American, Asian American, and Pacific Islander populations). If you fall into any of these categories, don’t wait for symptoms. A simple blood test can catch the problem years before you feel anything.
The Tests That Confirm a Diagnosis
Three main blood tests are used to diagnose diabetes. Each one measures blood sugar differently, and doctors sometimes use more than one to confirm results.
A1C Test
This measures your average blood sugar over the past two to three months as a percentage. No fasting required. The ranges are straightforward: below 5.7% is normal, 5.7% to 6.4% is prediabetes, and 6.5% or higher indicates diabetes. It’s the most convenient test because you can take it at any time of day regardless of when you last ate.
Fasting Blood Sugar Test
You fast overnight (at least eight hours), then have blood drawn in the morning. A result below 100 mg/dL is normal. Between 100 and 125 mg/dL falls in the prediabetes range. A reading of 126 mg/dL or higher, confirmed on a second test, means diabetes.
Oral Glucose Tolerance Test
This one takes longer. After fasting overnight, you have your blood drawn, then drink a sugary solution containing 75 grams of glucose. Your blood is drawn again one and two hours later. At the two-hour mark, below 140 mg/dL is normal, 140 to 199 mg/dL signals prediabetes, and 200 mg/dL or higher points to diabetes. This test is especially useful for catching prediabetes that other tests might miss.
Gestational Diabetes Screening
Pregnant women are typically screened between 24 and 28 weeks. The initial test doesn’t require fasting: you drink a glucose solution, and your blood is checked one hour later. If that reading comes back at 140 mg/dL or higher, you’ll return for a longer fasting version of the test. If your blood sugar is elevated at two or more time points during that follow-up, you have gestational diabetes. A reading of 200 mg/dL or more on the initial screen may indicate type 2 diabetes rather than gestational diabetes.
Can You Test at Home?
Over-the-counter A1C kits exist and can give you a general sense of where your blood sugar stands, but they’re notably less accurate than lab testing. A University of Florida Health study tested three home A1C kits against standard lab results using samples from 219 people with diabetes. To be considered accurate, a home test needed to land within 5% of the lab value at least 90% of the time. The best-performing kit met that standard in only 82% of samples. The other two hit it just 46% and 29% of the time.
That doesn’t make home kits useless. If you live in a rural area or have trouble getting to a doctor, a home result can start a productive conversation with your provider. But the result shouldn’t be used to rule diabetes in or out on its own, and it’s not precise enough to guide medication decisions. A lab-drawn blood test remains the standard for an actual diagnosis.
What Prediabetes Means for You
If your numbers land in the prediabetes range (A1C of 5.7% to 6.4%, or fasting glucose of 100 to 125 mg/dL), your blood sugar is higher than normal but hasn’t crossed the diabetes threshold. This isn’t just a warning label. Prediabetes means your body is already struggling to manage insulin effectively, and without changes, the progression to type 2 diabetes is common. The good news is that this stage responds well to lifestyle shifts. Modest weight loss (even 5% to 7% of body weight), regular physical activity, and dietary changes can delay or prevent the transition to diabetes entirely. Prediabetes is the window where you have the most leverage.