The most reliable way to know if you have diabetes is through a blood test ordered by your doctor, but your body often sends warning signs first. About 8 in 10 people with prediabetes don’t even know they have it, so if you’re wondering whether something feels off, you’re asking the right question. Here’s what to look for and what the testing process actually involves.
Symptoms That Should Get Your Attention
The three hallmark signs of diabetes are peeing more often than usual, feeling unusually thirsty, and staying hungry even after you’ve eaten a full meal. These happen because when blood sugar stays elevated, your kidneys work overtime to filter out the excess glucose, pulling water with it. That extra urination leaves you dehydrated, which triggers thirst. And because your cells aren’t absorbing glucose properly, your body signals that it needs more fuel, even when your stomach is full.
Beyond those big three, watch for:
- Unexplained weight loss, especially if you haven’t changed your diet or exercise habits
- Blurry vision that comes and goes
- Cuts or sores that heal slowly
- Tingling or numbness in your hands or feet
- Fatigue that doesn’t improve with rest
Not everyone gets obvious symptoms. Type 2 diabetes in particular can develop gradually over years, and many people feel fine during that time. Type 1 diabetes tends to come on faster and more dramatically, often over weeks, and is more common in children and young adults. If you suddenly feel extremely thirsty, lose weight rapidly, or start urinating constantly, that warrants a prompt visit to your doctor.
Physical Signs You Can See
One visible clue that often goes unrecognized is dark, velvety patches of skin in body folds, most commonly the back of the neck, armpits, and groin. This condition, called acanthosis nigricans, develops in most people who have become resistant to insulin. The patches may feel thicker than surrounding skin, sometimes itch, and can develop small skin tags. If you’ve noticed these changes, they’re worth mentioning to your doctor even if you have no other symptoms.
Frequent yeast infections or urinary tract infections can also be an early sign, since elevated blood sugar creates an environment where bacteria and yeast thrive.
Who Should Get Screened Without Symptoms
The U.S. Preventive Services Task Force recommends that adults aged 35 to 70 who are overweight or obese get screened for prediabetes and type 2 diabetes, even if they feel perfectly healthy. “Overweight” in this context means a BMI of 25 or higher.
Screening should start earlier or at a lower BMI for certain groups. If you’re Asian American, screening is recommended at a BMI of 23 or above. If you’re American Indian, Alaska Native, Black, Hispanic or Latino, or Native Hawaiian or Pacific Islander, earlier screening is appropriate because these populations have a higher prevalence of diabetes. A family history of diabetes, a history of gestational diabetes, or a diagnosis of polycystic ovary syndrome also raises your risk enough to justify earlier testing.
The Tests That Actually Diagnose Diabetes
A home glucose meter can help you manage diabetes once you have it, but it isn’t considered accurate enough to make an initial diagnosis. Diagnosis requires a laboratory blood draw. Your doctor will typically order one of three tests.
A1C Test
This measures your average blood sugar over the past two to three months. No fasting required. The results break down like this:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
Fasting Blood Glucose
You fast overnight (at least 8 hours), then have blood drawn. A fasting level 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 indicates diabetes.
Oral Glucose Tolerance Test
This one takes longer. You fast overnight, drink a sugary solution at the lab, and then have your blood drawn two hours later. A two-hour reading of 200 mg/dL or higher means diabetes. This test is less commonly used for routine screening but is the standard method during pregnancy.
In most cases, an abnormal result needs to be confirmed with a second test on a different day before a formal diagnosis is made. The exception: if your blood sugar is 200 mg/dL or higher on a random (non-fasting) blood draw and you already have classic symptoms like excessive thirst and frequent urination, that’s enough for a diagnosis on its own.
What Prediabetes Means for You
If your results land in the prediabetes range, your blood sugar is elevated but not high enough for a diabetes diagnosis. This isn’t just a warning label. Prediabetes means your body is already struggling to manage glucose effectively, and without changes, it commonly progresses to full type 2 diabetes.
The encouraging part is that prediabetes is often reversible. Losing 5% to 7% of your body weight (about 10 to 14 pounds for someone who weighs 200) and getting 150 minutes of moderate activity per week has been shown to cut the risk of developing type 2 diabetes significantly. These don’t have to be dramatic changes. Walking briskly for 30 minutes five days a week counts.
Screening During Pregnancy
Gestational diabetes develops during pregnancy in people who didn’t have diabetes before. Most pregnant people are screened between 24 and 28 weeks with a glucose challenge test. You drink a sugary solution, and your blood sugar is checked one hour later. A reading below 140 mg/dL is typically considered normal. A result of 190 mg/dL or higher means gestational diabetes. If your result falls between those numbers, you’ll do a longer follow-up test where your blood is checked every hour for three hours after drinking an even sweeter solution. Two or more elevated readings on that test confirm the diagnosis.
Gestational diabetes usually resolves after delivery, but it increases your lifetime risk of developing type 2 diabetes later, which makes follow-up screening in the years after pregnancy important.
When Symptoms Become an Emergency
In rare cases, diabetes announces itself as a medical emergency. This is more common with type 1 diabetes but can happen with type 2 as well. A dangerous complication called diabetic ketoacidosis occurs when the body, starved of usable glucose, starts breaking down fat at an extreme rate, producing acids that build up in the blood.
The warning signs include fast and deep breathing, breath that smells fruity or sweet, nausea and vomiting, confusion, and extreme fatigue. If you or someone around you has multiple symptoms from that list, that’s a 911 situation. Ketoacidosis can become life-threatening within hours.