Prediabetes means your blood sugar is higher than normal but not yet high enough for a type 2 diabetes diagnosis. It’s defined by specific lab values: an A1C between 5.7% and 6.4%, a fasting blood sugar between 100 and 125 mg/dL, or a two-hour glucose tolerance result between 140 and 199 mg/dL. More than 115 million American adults currently have prediabetes, and 8 in 10 of them don’t know it.
The Three Tests That Define Prediabetes
There are three standard blood tests used to identify prediabetes, and any one of them can make the diagnosis.
- A1C test: Measures your average blood sugar over the past two to three months. A result of 5.7% to 6.4% falls in the prediabetes range. Below 5.7% is normal, and 6.5% or higher is diabetes.
- Fasting blood sugar: Taken after at least eight hours without eating. A result of 100 to 125 mg/dL is prediabetes. Normal is below 100, and 126 or higher is diabetes.
- Oral glucose tolerance test (OGTT): You drink a sugary solution, then your blood sugar is measured two hours later. A result of 140 to 199 mg/dL is prediabetes. Normal is below 140, and 200 or higher is diabetes.
These tests don’t always agree with each other. You might have a normal fasting blood sugar but an elevated A1C, or vice versa. Your doctor may repeat a test or use a second method to confirm. The A1C is convenient because it doesn’t require fasting, but certain conditions can throw off the result, including severe anemia, kidney failure, liver disease, sickle cell anemia, thalassemia, recent blood transfusions, and pregnancy. If any of these apply to you, a fasting blood sugar or glucose tolerance test is more reliable.
What’s Happening Inside Your Body
Prediabetes isn’t just a number on a lab slip. It reflects real changes in how your body handles sugar. Normally, your pancreas releases insulin after you eat, and that insulin signals your muscles, liver, and fat cells to absorb sugar from your blood. In prediabetes, those tissues start ignoring insulin’s signal, a problem called insulin resistance. Your muscles take in less sugar, and your liver keeps releasing sugar it should hold onto.
To compensate, your pancreas pumps out more insulin. For a while, this extra effort keeps your blood sugar in a near-normal range. But the pancreas can only work overtime for so long. Over months and years, the insulin-producing cells gradually wear down and lose their ability to keep up with demand. Prediabetes is the stage where this mismatch is already measurable but hasn’t yet tipped into full diabetes.
Excess body fat, particularly fat stored around the organs and within muscle tissue, is the primary driver of insulin resistance. This type of fat releases inflammatory signals and fatty acids that directly interfere with insulin’s ability to do its job. You don’t have to be significantly overweight for this to happen. People at a normal weight can still carry enough internal fat to develop insulin resistance.
Why Prediabetes Isn’t a “Harmless” Warning
Many people hear “pre” and assume nothing is actually wrong yet. That’s not quite true. Research from the Maastricht Study found that people with prediabetes already show measurable changes in the tiny blood vessels of the eyes and skin. The decline in small-vessel function during prediabetes is roughly one-quarter to one-half as severe as what’s seen in people with full diabetes. Damage to these small blood vessels is what eventually drives complications like vision loss, kidney disease, nerve damage, and even some forms of heart failure.
Larger blood vessels are affected too. The stiffening and dysfunction of arteries that leads to heart attacks and strokes appears to begin during prediabetes, not after a diabetes diagnosis. Researchers call this the “ticking clock hypothesis”: the clock on cardiovascular damage starts running before diabetes officially arrives.
How Likely Is It to Become Diabetes?
Without any changes, roughly 5 to 10% of people with prediabetes progress to type 2 diabetes each year. Over a decade, the overall probability is about 12.5%. That risk climbs to around 16% for people whose fasting blood sugar sits in the higher end of the prediabetes range.
Those numbers also mean the majority of people with prediabetes do not develop diabetes within ten years, especially if they take action. Prediabetes can be reversed. A large clinical trial called the Diabetes Prevention Program found that modest lifestyle changes reduced the risk of developing type 2 diabetes by 58%. The intervention wasn’t extreme: participants aimed to lose 7% of their body weight (about 14 pounds for a 200-pound person) and get 150 minutes of moderate physical activity per week, like brisk walking. A common medication used as a comparison reduced risk by 31%, a meaningful benefit but roughly half as effective as lifestyle changes alone.
Symptoms You Might Notice
Prediabetes is mostly silent. Most people feel completely fine, which is why the vast majority don’t know they have it. There are no reliable symptoms that alert you the way a fever signals an infection.
One visible clue does exist, though it doesn’t appear in everyone. Some people with insulin resistance develop dark, thick, velvety patches of skin, typically in the armpits, groin, or on the back of the neck. This condition, called acanthosis nigricans, develops slowly and can be itchy or have a slight odor. Skin tags in these same areas are also common. If you notice these skin changes, they’re worth mentioning to a doctor, because they’re strongly linked to insulin resistance and an elevated risk of type 2 diabetes.
Who Should Get Tested
Screening is recommended for all adults starting at age 35, and earlier if you carry extra weight combined with at least one additional risk factor. Those risk factors include having a parent or sibling with type 2 diabetes, a history of gestational diabetes, belonging to a higher-risk ethnic group (African American, Hispanic, Native American, Asian American, or Pacific Islander), having polycystic ovary syndrome, or being physically inactive. If your results come back normal, repeat testing every three years is typical.
What Actually Works to Reverse It
The single most effective intervention is sustained, moderate weight loss combined with regular physical activity. You don’t need to reach an ideal body weight. Losing just 5 to 7% of your current weight meaningfully improves insulin sensitivity, and the benefits are measurable within weeks. Physical activity helps independently of weight loss because working muscles pull sugar from the blood without needing as much insulin.
The type of exercise matters less than consistency. Walking, cycling, swimming, and strength training all improve how your body uses insulin. Strength training is particularly useful because building muscle mass increases the total tissue available to absorb blood sugar. Even short walks after meals can blunt post-meal blood sugar spikes.
Dietary changes don’t need to follow a single rigid plan. The consistent finding across studies is that reducing refined carbohydrates and added sugars, increasing fiber from vegetables and whole grains, and eating moderate portions produces results. No specific diet has proven dramatically superior to another for prediabetes, so the best approach is one you can actually maintain.
For people who struggle with lifestyle changes alone or whose blood sugar sits at the higher end of the prediabetes range, medication is sometimes prescribed. It’s less effective than lifestyle changes on its own but can be a useful addition. The decision depends on your individual risk profile and how your numbers trend over time.