Nearly half of all people with type 2 diabetes don’t know they have it. An estimated 240 million adults worldwide are living with undiagnosed diabetes, and about 60% of people with type 2 diabetes have no noticeable symptoms at the time of diagnosis. That means you can’t always “tell” from how you feel alone. But there are warning signs worth knowing, and simple blood tests that give a definitive answer.
The Classic Warning Signs
The most recognizable symptoms of type 2 diabetes trace back to one problem: too much sugar in your blood. When blood sugar climbs above roughly 180 mg/dL, your kidneys can no longer reabsorb all that glucose. It spills into your urine, pulling extra water along with it. That’s why frequent urination is often the first thing people notice, sometimes producing more than 3 liters of urine a day (normal is 1 to 2 liters). All that fluid loss triggers persistent thirst, which leads to drinking more, which leads to more urination. The cycle feeds itself.
Fatigue is the other hallmark. When your cells can’t efficiently use glucose for energy, you feel drained even after a full night’s sleep. Some people describe it as a heaviness that doesn’t improve with rest. Unexplained weight loss can also occur, though this is more common in type 1 diabetes. In type 2, weight changes tend to be subtler or absent altogether.
Blurred vision is another early signal that often gets blamed on aging or screen time. High blood sugar causes the lens of your eye to swell, temporarily shifting your focus. If your vision seems to fluctuate from day to day, that pattern is worth paying attention to.
Skin Changes and Physical Signs
One visible clue that many people overlook is a skin condition called acanthosis nigricans: dark, velvety patches that appear in body creases like the neck, armpits, groin, or sometimes the elbows and knuckles. These patches signal insulin resistance, meaning your body is producing insulin but struggling to use it effectively. Acanthosis nigricans can show up years before a diabetes diagnosis, making it one of the earliest physical markers of prediabetes or type 2 diabetes.
Slow Healing and Nerve Symptoms
If small cuts, scrapes, or bruises seem to linger for weeks, high blood sugar may be interfering with your body’s repair process. Elevated glucose keeps wounds stuck in a prolonged inflammatory state. The cells responsible for closing a wound, rebuilding tissue, and forming new blood vessels all function poorly in a high-sugar environment. Skin cells migrate more slowly, scar-forming cells don’t activate properly, and blood flow to the area is reduced. The result is healing that stalls where it normally wouldn’t.
Tingling, numbness, or a “pins and needles” sensation in your feet is another red flag. This is the earliest stage of nerve damage from sustained high blood sugar, and it typically starts in the feet before moving to the hands. Some people notice increased sensitivity or burning pain, especially at night. If these sensations are interfering with sleep or daily activities, that’s a strong reason to get tested.
Symptoms That Affect Women Specifically
Women with undiagnosed type 2 diabetes are more likely to experience recurrent vaginal yeast infections and urinary tract infections. The reason is straightforward: excess sugar in your urine creates an environment where yeast and bacteria thrive. One yeast infection isn’t cause for alarm. But if they keep coming back, especially alongside other symptoms on this list, it’s worth checking your blood sugar levels.
Why You Might Have No Symptoms at All
Type 2 diabetes develops gradually, often over years. Blood sugar rises slowly enough that your body adapts, and the symptoms can be so mild you chalk them up to stress, aging, or a busy schedule. That 60% asymptomatic rate at diagnosis isn’t a fluke. It reflects how quietly this disease can progress. By the time obvious symptoms appear, blood sugar levels may have been elevated long enough to cause early damage to nerves, blood vessels, and kidneys.
This is why screening matters even if you feel fine.
Who Should Get Screened
The U.S. Preventive Services Task Force recommends routine diabetes screening for adults aged 35 to 70 who are overweight or obese (a BMI of 25 or higher). That starting age was recently lowered from 40 to 35. If you’re Asian American, screening is recommended at a lower BMI threshold of 23. And if you’re American Indian, Alaska Native, Black, Hispanic/Latino, or Native Hawaiian/Pacific Islander, screening may be appropriate even younger than 35, since these populations face a disproportionately higher risk.
Family history of diabetes, a personal history of gestational diabetes, or a diagnosis of polycystic ovary syndrome also move you into the “get tested sooner” category.
The Tests That Confirm a Diagnosis
Three blood tests are used to diagnose type 2 diabetes, and your doctor may use one or a combination.
- A1C test: This measures your average blood sugar over the past 2 to 3 months. An A1C below 5.7% is normal. Between 5.7% and 6.4% falls in the prediabetes range. An A1C of 6.5% or higher indicates diabetes. No fasting is required.
- Fasting blood sugar test: You fast overnight, then have your blood drawn in the morning. A result of 126 mg/dL or above indicates diabetes.
- Glucose tolerance test: You drink a sugary solution, then have your blood sugar measured two hours later. A reading at or above 200 mg/dL indicates diabetes.
A single abnormal result is usually confirmed with a second test on a different day before a formal diagnosis is made. The exception is if you have classic symptoms and a random blood sugar reading above 200 mg/dL, which can be enough on its own.
What Prediabetes Means for You
If your results land in the prediabetes range (A1C of 5.7% to 6.4%, or fasting blood sugar of 100 to 125 mg/dL), your blood sugar is elevated but not yet at the diabetes threshold. This isn’t just a warning label. Prediabetes is the stage where lifestyle changes have the greatest impact. Losing 5% to 7% of your body weight and getting about 150 minutes of moderate activity per week has been shown to cut the risk of progressing to type 2 diabetes by more than half. Not everyone with prediabetes develops diabetes, but without changes, many do within 5 to 10 years.