Prediabetic means your blood sugar is higher than normal but not high enough to be classified as type 2 diabetes. It’s a warning stage where your body is losing its ability to manage glucose efficiently, and without changes, it can progress to full diabetes. More than 115 million American adults have prediabetes, and 8 in 10 of them don’t know it.
The Blood Sugar Numbers That Define Prediabetes
Prediabetes is diagnosed through one of three common blood tests, each with a specific range that falls between normal and diabetic:
- A1C test: 5.7% to 6.4% (this reflects your average blood sugar over the past two to three months)
- Fasting blood sugar: 100 to 125 mg/dL (taken after not eating for at least 8 hours)
- Glucose tolerance test: 140 to 199 mg/dL two hours after drinking a sugary solution
Any result at or above the top of these ranges crosses into diabetes territory. Your doctor may use one or more of these tests, and a single borderline result is usually confirmed with a repeat test.
What’s Happening Inside Your Body
Your pancreas produces insulin, a hormone that acts like a key to unlock your cells so they can absorb sugar from your blood. In prediabetes, two things start going wrong, sometimes simultaneously.
First, your cells become resistant to insulin. The key still fits the lock, but the door gets harder to open. Your muscles, liver, and fat tissue stop responding to insulin as well as they should, so sugar builds up in the bloodstream instead of being absorbed. Excess body weight is one of the strongest drivers of this resistance, because fat tissue actively interferes with insulin signaling.
Second, the insulin-producing cells in your pancreas start to struggle. Initially, they compensate by pumping out more insulin to overcome the resistance. But over time, this extra workload wears them down. They lose their ability to sense blood sugar levels accurately and produce insulin in the right amounts. Once these cells are damaged enough, they can’t keep up, and blood sugar stays elevated.
The combination of resistant cells and an overtaxed pancreas is what pushes someone from normal blood sugar into prediabetes, and eventually into type 2 diabetes if nothing changes.
Why Prediabetes Isn’t “Just” a Warning
It’s tempting to think of prediabetes as a harmless heads-up, but damage can begin before blood sugar reaches diabetic levels. Research shows that the complications traditionally associated with diabetes, including nerve damage, kidney changes, and blood vessel injury, can start during the prediabetic stage in susceptible people.
Nerve damage is the most common early complication. Between 11% and 25% of people with prediabetes already have peripheral neuropathy, and 13% to 21% experience neuropathic pain. The small nerve fibers that carry pain and temperature signals and regulate functions like heart rate and digestion are particularly vulnerable. In fact, 18% to 25% of people newly diagnosed with diabetes already show measurable nerve dysfunction, meaning the damage started before they crossed the diagnostic threshold.
The kidneys are also affected. Even moderately elevated blood sugar increases the risk of early kidney changes like abnormal protein in the urine and excessive filtering by the kidneys, both of which signal stress on the organ. These aren’t guaranteed outcomes for everyone with prediabetes, but they challenge the idea that organ damage only begins at the point of a diabetes diagnosis.
How Likely Is Progression to Diabetes?
Without any lifestyle changes, roughly 25% of people with prediabetes develop type 2 diabetes within three to five years. Up to 37% progress within four years. Over a lifetime, as many as 70% of people with prediabetes will eventually develop the full condition. These numbers make prediabetes one of the strongest predictors of future diabetes, but they also leave a large window for intervention.
Physical Signs You Might Notice
Prediabetes rarely causes obvious symptoms, which is why so many people have it without knowing. One visible clue is a skin condition called acanthosis nigricans: patches of dark, thick, velvety skin that develop slowly in body folds like the back of the neck, armpits, or groin. These patches may be itchy or have a slight odor, and small skin tags sometimes appear in the same areas. The darkening is driven by high insulin levels in the blood, so it’s strongly linked to insulin resistance. If you notice these skin changes, it’s worth getting your blood sugar checked.
What Actually Reduces the Risk
The most convincing evidence for reversing prediabetes comes from the Diabetes Prevention Program, a large clinical trial that tested intensive lifestyle changes against medication. Participants who lost 7% of their body weight (about 14 pounds for a 200-pound person) and exercised at moderate intensity for 150 minutes per week reduced their risk of developing diabetes by 58%. That’s a striking result from changes that don’t require extreme measures. A brisk 30-minute walk five days a week meets the exercise target, and the weight loss goal is modest enough to be sustainable.
The weight loss matters more than any specific diet. Losing that 7% improves how your cells respond to insulin and reduces the workload on your pancreas. Exercise helps independently by allowing your muscles to absorb blood sugar even when insulin signaling is impaired.
When Medication Enters the Picture
For people at particularly high risk, the American Diabetes Association recommends considering medication alongside lifestyle changes. The highest-risk group includes adults aged 25 to 59 with a BMI of 35 or above, fasting blood sugar at 110 mg/dL or higher, an A1C of 6.0% or above, or a history of gestational diabetes. For these individuals, medication can provide additional protection while lifestyle changes take effect. But for most people with prediabetes, weight loss and exercise remain the first and most effective approach.