Prediabetes means your blood sugar levels are higher than normal but not yet high enough to qualify as type 2 diabetes. It’s a warning stage, a window where your body is already struggling to manage glucose effectively but hasn’t crossed the threshold into full diabetes. More than 115 million American adults have prediabetes, and 8 in 10 of them don’t know it.
How Prediabetes Is Defined by the Numbers
Prediabetes is diagnosed through one of three blood tests, each measuring glucose in a different way:
- A1C test: 5.7% to 6.4%. This reflects your average blood sugar over the past two to three months.
- Fasting blood glucose: 100 to 125 mg/dL. This is measured after not eating for at least eight hours.
- Oral glucose tolerance test: 140 to 199 mg/dL two hours after drinking a sugary solution. This shows how efficiently your body clears a spike of glucose.
Below those ranges is normal. At or above the upper end, you’re in type 2 diabetes territory. Any one of these tests falling in the prediabetic range is enough for a diagnosis, though your doctor may repeat the test to confirm.
What’s Happening Inside Your Body
Prediabetes is driven by insulin resistance, a condition where your cells stop responding properly to insulin, the hormone that lets glucose move from your blood into your muscles, liver, and fat tissue for energy.
When you consistently take in more calories than your body needs, fat builds up inside muscle and liver cells. This excess fat triggers a chain reaction that interferes with insulin’s ability to do its job. In muscle tissue, glucose absorption slows. In the liver, things get worse in two ways: the liver keeps producing new glucose even when blood sugar is already elevated, and it starts converting excess sugar into even more fat. That fat gets deposited in and around your organs, fueling more insulin resistance in a self-reinforcing loop.
Your pancreas tries to compensate by pumping out more and more insulin. For a while, this extra effort keeps blood sugar roughly in check, though levels creep upward. Prediabetes is essentially the phase where your pancreas is working overtime but starting to fall behind. If the cycle continues unchecked, the insulin-producing cells in the pancreas eventually can’t keep up with demand, and blood sugar rises into the diabetic range.
Symptoms You Might Notice
Prediabetes is often called a “silent” condition because most people feel perfectly fine. There are no dramatic symptoms that send you to the doctor. That’s precisely why the vast majority of people who have it are unaware.
One visible clue is darkened, velvety patches of skin, a condition called acanthosis nigricans. These patches typically appear on the neck, armpits, or groin and signal that your body is producing excess insulin. Skin tags in those same areas can also be a marker. These signs aren’t guaranteed, but if you notice them, they’re worth mentioning to your doctor. Blurred vision, increased thirst, and frequent urination are signs that prediabetes may have already progressed to type 2 diabetes.
The Risk of Progressing to Type 2 Diabetes
Without any changes, roughly 1 in 8 people with prediabetes will develop type 2 diabetes within 10 years. That may sound modest, but the risk compounds over time, and it varies significantly based on weight, activity level, family history, and how insulin resistant you already are. Some people progress faster, others stay in the prediabetic range for years, and some return to normal blood sugar levels entirely.
The progression isn’t inevitable. The landmark Diabetes Prevention Program study found that people who lost 7% of their body weight (about 14 pounds for someone weighing 200) and exercised at moderate intensity for 150 minutes per week reduced their risk of developing type 2 diabetes by 58%. That’s a brisk walk for about 30 minutes, five days a week. After 10 years of follow-up, the benefit held. This remains one of the most replicated findings in diabetes research.
Damage Can Start Before Diabetes
Many people assume prediabetes is harmless because it isn’t “real” diabetes. That’s not accurate. The slightly elevated blood sugar and insulin resistance of prediabetes are already affecting your blood vessels.
People with prediabetes have a 2.2-fold higher rate of death from all causes compared to those with normal blood sugar. The lining of blood vessels begins to lose its ability to relax and expand properly, a condition called endothelial dysfunction. This promotes inflammation and makes arteries stiffer, setting the stage for cardiovascular problems. A large meta-analysis of over 1.6 million people found that prediabetes was associated with a 13% to 30% higher risk of cardiovascular disease and a 6% to 20% higher risk of stroke, depending on the type of blood sugar abnormality.
Even the smallest blood vessels are affected. Studies have found that people with prediabetes show reduced blood vessel responses in the retina, similar to patterns seen in people who already have diabetes. There’s also an 11% increased risk of kidney dysfunction after adjusting for other risk factors. These findings reinforce that prediabetes is not simply a label. It’s an active metabolic state with real consequences for your heart, kidneys, and eyes.
How Diet and Exercise Help
The core strategy for reversing prediabetes is straightforward: reduce the calorie surplus that drives fat accumulation in your muscles and liver, and increase the physical activity that helps your cells use glucose more effectively.
On the diet side, the type of carbohydrates you eat matters as much as the amount. Foods with a low glycemic index, meaning they raise blood sugar slowly and moderately, produce smaller glucose spikes after meals. In clinical trials, people with prediabetes who followed a low-glycemic diet had lower post-meal blood sugar levels and needed less insulin to process those meals compared to those eating high-glycemic foods. Practically, this means choosing whole grains over refined grains, pairing carbohydrates with protein or fat to slow digestion, and favoring foods like legumes, most vegetables, and intact whole grains over white bread, sugary cereals, and processed snacks.
Exercise works through a separate mechanism. When muscles contract during physical activity, they absorb glucose from the blood even without insulin’s help. Regular activity also reduces the fat stored inside muscle cells, which directly improves insulin sensitivity over time. The 150-minutes-per-week target from the Diabetes Prevention Program doesn’t require intense gym sessions. Walking, cycling, swimming, or any sustained movement that raises your heart rate counts.
How Often to Get Tested
Once you’ve been identified as prediabetic, follow-up testing every 6 to 12 months is generally recommended, especially if you have additional risk factors like obesity, a family history of diabetes, or a history of gestational diabetes. The A1C test is the most convenient option for monitoring because it doesn’t require fasting and captures your average blood sugar over months rather than a single snapshot.
Tracking your numbers over time tells you whether your lifestyle changes are working. An A1C that drops from 6.2% to 5.5% means you’ve moved back into the normal range. One that climbs from 6.0% to 6.5% means you’ve crossed into diabetes. These aren’t abstract numbers; they directly reflect what’s happening in your blood vessels, your pancreas, and your long-term health trajectory.