About 1 in 20 U.S. adults has diabetes and doesn’t know it. That’s roughly 11 million people walking around with elevated blood sugar and no diagnosis, according to CDC data from 2021 to 2023. The reason so many cases go undetected is that diabetes, especially Type 2, often develops gradually and can be completely silent for years. But there are warning signs your body may be sending, and simple blood tests that give a definitive answer.
The Classic Warning Signs
The symptoms most strongly linked to diabetes all trace back to one problem: too much sugar in your blood. When glucose builds up beyond what your kidneys can reabsorb, the excess spills into your urine, pulling water along with it. That’s why frequent urination is one of the earliest signs. Your body then tries to replace all that lost fluid, which triggers intense thirst. You may find yourself drinking far more water than usual and still feeling parched.
Other common symptoms include:
- Unexplained weight loss, particularly with Type 1 diabetes, because your body can’t use glucose for energy and starts burning fat and muscle instead
- Constant hunger, even after eating, because your cells aren’t getting the fuel they need
- Fatigue that doesn’t improve with rest
- Blurry vision, caused by high blood sugar changing the shape of your eye’s lens
With Type 1 diabetes, these symptoms tend to appear suddenly, often over a few weeks, and they’re usually intense enough that you seek medical help quickly. Type 1 can start at any age but often shows up during childhood or the teen years. Type 2 diabetes is a different story. It’s far more common, typically develops after age 40 (though it’s increasingly seen in younger people), and the symptoms can be so mild or gradual that you chalk them up to aging, stress, or just being busy.
Subtle Signs You Might Miss
Beyond the classic symptoms, diabetes produces a set of quieter changes that many people don’t connect to blood sugar at all.
Slow-healing cuts and bruises. High blood sugar damages blood vessels and disrupts normal circulation, which means less oxygen and fewer immune cells reach wounds. At the same time, your body gets stuck in a prolonged inflammatory state: the immune cells that normally clean up damaged tissue and shift into repair mode keep pumping out inflammatory signals instead. The result is that a small cut or scrape that should heal in a week lingers for weeks or even months.
Tingling, numbness, or pain in your feet. Nerve damage from elevated blood sugar usually starts in the feet and can feel like pins and needles, burning, or increased sensitivity, particularly at night. Some people notice the opposite: a loss of feeling that makes it hard to sense temperature or pain. This often develops so slowly that you don’t realize it until someone points out a blister or sore you never felt.
Dark, velvety skin patches. Darkened, slightly thickened skin in the folds of your neck, armpits, or groin is a condition strongly associated with insulin resistance. These patches develop gradually, feel soft or velvety to the touch, and may be accompanied by skin tags in the same area. If you’ve noticed this kind of skin change, it’s worth getting your blood sugar checked.
Frequent infections. Yeast infections, urinary tract infections, and skin infections can all occur more often when blood sugar is elevated. High glucose creates a favorable environment for bacteria and yeast, and your immune system doesn’t function as efficiently when sugar levels stay high.
How Type 1 and Type 2 Feel Different
If you’re trying to figure out whether something is wrong, timing matters. Type 1 diabetes tends to announce itself. Symptoms come on fast, they’re hard to ignore, and people often feel genuinely sick, sometimes landing in the emergency room with dangerously high blood sugar before they even have a diagnosis.
Type 2 is the quiet version. Many people with prediabetes or early Type 2 diabetes have no symptoms at all. You might feel a little more tired than usual or notice you’re getting up to use the bathroom more at night, but nothing dramatic enough to trigger alarm. That’s exactly why routine screening matters: you can have blood sugar levels high enough to cause damage to your eyes, nerves, and kidneys long before you feel anything obvious.
Gestational Diabetes During Pregnancy
Gestational diabetes develops around the 24th week of pregnancy and usually produces no noticeable symptoms. Some women feel slightly thirstier than normal or urinate more frequently, but those overlap so much with normal pregnancy that they’re easy to dismiss. That’s why standard prenatal care includes a glucose screening test between weeks 24 and 28. If you’re pregnant and haven’t been offered this test, ask about it.
The Blood Tests That Confirm a Diagnosis
Symptoms can raise suspicion, but a diagnosis requires blood work. Three tests are commonly used, and each measures blood sugar in a slightly different way.
A1C test. This measures your average blood sugar over the past two to three months. It doesn’t require fasting. An A1C below 5.7% is normal, 5.7% to 6.4% indicates prediabetes, and 6.5% or higher means diabetes.
Fasting blood glucose. This is a snapshot of your blood sugar after not eating for at least eight hours, usually first thing in the morning. A result under 100 mg/dL is normal, 100 to 125 mg/dL falls in the prediabetes range, and 126 mg/dL or higher points to diabetes.
Oral glucose tolerance test. You drink a sugary solution, then have your blood drawn two hours later to see how well your body processes that sugar load. Under 140 mg/dL is normal, 140 to 199 mg/dL suggests prediabetes, and 200 mg/dL or higher indicates diabetes.
In most cases, an abnormal result needs to be confirmed with a second test on a different day. The exception is if you already have clear symptoms of high blood sugar along with a random blood glucose reading of 200 mg/dL or higher, which is enough for a diagnosis on its own.
What Happens If It Goes Undetected
Uncontrolled diabetes doesn’t just cause uncomfortable symptoms. Over time, it damages organs in ways that are difficult to reverse.
Your eyes are especially vulnerable. High blood sugar weakens the tiny blood vessels in the retina, causing them to swell, leak, and eventually bleed. This process, called diabetic retinopathy, affects both eyes and is the leading cause of blindness in working-age adults. In the early stages you may not notice anything at all. By the time dark spots appear in your vision or things look blurry, significant damage has already occurred. People with diabetes are also twice as likely to develop glaucoma and tend to develop cataracts at a younger age.
Nerve damage progresses from the tingling and numbness described earlier into a loss of sensation that makes injuries easy to miss. Combined with poor wound healing, this is why diabetes is the leading cause of non-traumatic limb amputations. The same nerve damage can also affect digestion, bladder function, and sexual health.
Who Should Get Tested
If you searched for this topic because something feels off, getting a simple blood test is the fastest way to either catch a problem early or put your mind at ease. But even without symptoms, screening is recommended if you’re 35 or older, carry extra weight (particularly around your midsection), have a family history of diabetes, had gestational diabetes during a pregnancy, or belong to a population with higher diabetes rates, including Black, Hispanic, Native American, and Asian American communities.
Prediabetes is not a guarantee that you’ll develop full diabetes. It’s a window where lifestyle changes, especially modest weight loss and regular physical activity, can bring blood sugar back to normal levels. About 98 million U.S. adults have prediabetes, and most don’t know it. A single fasting blood test or A1C can tell you where you stand.