Prediabetes is defined by blood sugar levels that are higher than normal but not yet high enough to qualify as type 2 diabetes. Three specific lab tests can identify it: a fasting blood glucose of 100 to 125 mg/dL, an A1C of 5.7% to 6.4%, or a two-hour oral glucose tolerance test result of 140 to 199 mg/dL. Any one of those results puts you in the prediabetes range. More than 115 million American adults have it, and roughly 8 in 10 of them don’t know.
The Three Tests and Their Numbers
Doctors use three different blood tests to check for prediabetes, and each one measures blood sugar in a slightly different way. You only need one abnormal result for a prediabetes diagnosis, though your doctor may repeat the test or order a second type to confirm.
Fasting blood glucose measures your blood sugar after at least eight hours without eating. A normal result is below 100 mg/dL. A reading of 100 to 125 mg/dL falls in the prediabetes range, and 126 mg/dL or higher on two separate occasions indicates diabetes.
A1C (hemoglobin A1C) reflects your average blood sugar over the past two to three months. It doesn’t require fasting, which makes it convenient. Normal is below 5.7%. Prediabetes falls between 5.7% and 6.4%, and 6.5% or higher means diabetes.
Oral glucose tolerance test (OGTT) checks how your body handles a sugar load. You drink a sugary solution, then have your blood drawn two hours later. A result of 140 to 199 mg/dL signals prediabetes. At 200 mg/dL or above, it’s diabetes.
These ranges don’t always agree with each other. Someone can have a normal fasting glucose but an elevated A1C, or vice versa. That’s partly because each test captures a different snapshot of how your body processes sugar. If one test comes back borderline, a second test type can clarify the picture.
What’s Happening Inside Your Body
Prediabetes involves two overlapping problems: your cells become less responsive to insulin, and the cells in your pancreas that produce insulin start to falter. Insulin is the hormone that moves sugar from your blood into your muscles, liver, and fat cells for energy. When those tissues stop responding efficiently, your pancreas compensates by pumping out more insulin. For a while, this extra effort keeps blood sugar in check.
Eventually, though, the insulin-producing cells can’t keep up with the demand. They become overworked, and their ability to sense and respond to rising blood sugar declines. The result is a slow, steady creep in blood sugar levels, first into the prediabetes range and potentially into diabetes territory. Fat accumulation, particularly around the organs and even within the pancreas itself, accelerates this process. Excess fat in and around pancreatic tissue can directly impair the cells that make insulin, creating a feedback loop where high blood sugar and high fat levels compound each other’s damage.
This is why prediabetes is so closely tied to weight. Carrying extra weight, especially around the midsection, desensitizes your tissues to insulin. Diets high in saturated fat worsen the problem by forcing cells to choose between processing fat and processing glucose, which drives blood sugar higher and further stresses the pancreas.
Why Most People Don’t Notice It
Prediabetes rarely produces obvious symptoms. Most people feel completely normal, which is why the vast majority of cases go undetected without a blood test. There are, however, a few subtle physical signs worth knowing about.
The most recognizable is a skin change called acanthosis nigricans: patches of darkened, velvety skin that typically appear on the back of the neck, in the armpits, or in the groin. These patches develop because high insulin levels stimulate skin cell growth in areas where skin folds against itself. Small skin tags in the same areas can also be related. These signs don’t appear in everyone with prediabetes, but when they do, they’re a visible clue that insulin levels have been elevated for some time.
Some people notice increased thirst, more frequent urination, or mild fatigue, but these symptoms are vague enough that they’re easy to dismiss. The practical takeaway is that prediabetes is a condition you find through screening, not through waiting for symptoms to appear.
Who Should Get Screened
The U.S. Preventive Services Task Force recommends screening for prediabetes 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 lower BMI threshold of 23, because the risk of insulin resistance rises at a lower body weight in this population. Earlier screening is also warranted for people who are American Indian, Alaska Native, Black, Hispanic or Latino, or Native Hawaiian or Pacific Islander, groups that face disproportionately higher diabetes rates.
Certain medical history markers also increase your risk and may prompt earlier testing. Women who had gestational diabetes during pregnancy are at higher risk, and so are their children. Polycystic ovary syndrome (PCOS), a hormonal condition that affects roughly 1 in 10 women of reproductive age, is another well-established risk factor. A family history of type 2 diabetes, a sedentary lifestyle, and high blood pressure or abnormal cholesterol levels round out the list of common red flags.
How Likely Prediabetes Is to Become Diabetes
Prediabetes is not a guaranteed path to diabetes, but without changes, the odds are significant. Roughly 5% to 10% of people with prediabetes progress to type 2 diabetes each year. Over a lifetime, up to 70% of people with prediabetes will eventually develop the full condition. Those numbers vary depending on how many risk factors you carry, your age, and which specific blood sugar measure is elevated.
The flip side is more encouraging. Prediabetes is the stage where intervention makes the biggest difference. The landmark Diabetes Prevention Program trial showed that modest weight loss, around 5% to 7% of body weight, combined with 150 minutes of moderate physical activity per week reduced the risk of progressing to diabetes by 58%. For people over 60, the risk reduction was even higher. These aren’t extreme lifestyle overhauls. For someone who weighs 200 pounds, 5% means losing 10 pounds.
What Reversal Actually Looks Like
Bringing blood sugar back below the prediabetes threshold is possible, but “reversal” is a better word than “cure.” The underlying tendency toward insulin resistance doesn’t fully disappear; it’s managed. The goal is to reduce the workload on your pancreas enough that it can keep up with demand again.
The most effective strategies are the ones that directly address insulin resistance. Losing a moderate amount of weight reduces fat around the organs and within the pancreas, which improves how your cells respond to insulin. Regular physical activity helps independently of weight loss because working muscles pull sugar from the blood even without insulin’s help. Reducing refined carbohydrates and saturated fat eases the metabolic burden on both your liver and pancreas.
Sleep also plays a measurable role. Consistently getting fewer than six hours per night worsens insulin resistance, and improving sleep quality can improve blood sugar regulation even without dietary changes. Stress management matters for similar reasons: chronic stress hormones directly raise blood sugar and promote fat storage around the midsection.
For some people, particularly those whose blood sugar is at the higher end of the prediabetes range or who have multiple risk factors, medication like metformin may be recommended alongside lifestyle changes. But for most people in the prediabetes range, the evidence strongly favors lifestyle modification as the first and most effective approach.