Diabetes is surprisingly easy to develop, especially type 2. Nearly 16% of American adults already have it, and more than one in four of those people don’t even know it yet. The disease often builds silently over years, with no obvious symptoms until significant damage is already underway. Whether you develop it depends on a mix of genetics, daily habits, and in some cases, pure biological luck.
The answer also depends on which type of diabetes you’re asking about. Type 2, which accounts for roughly 90% of cases, is heavily influenced by lifestyle and is far more common. Type 1 is an autoimmune condition that strikes regardless of how healthy you are. Both are more common than most people realize.
Type 2 Diabetes Develops Gradually and Quietly
Type 2 diabetes doesn’t appear overnight. It typically starts with insulin resistance, a state where your cells stop responding efficiently to insulin, the hormone that moves sugar from your blood into your cells. Your pancreas compensates by producing more insulin, sometimes for years. The decline in your pancreas’s ability to keep up actually begins as early as 12 years before a formal diagnosis. By the time your blood sugar crosses into the diabetic range, the damage to your insulin-producing cells is already well advanced.
What makes type 2 so easy to develop is that this entire process is largely invisible. Symptoms like increased thirst, frequent urination, and blurry vision can take years to appear. Some people never notice symptoms at all. That’s why about 4.5% of U.S. adults have diabetes and don’t know it.
There’s a middle stage called prediabetes, where blood sugar is elevated but not yet in the diabetic range. Among people with mildly elevated fasting blood sugar, roughly 1.3% progress to full diabetes each year. For those with higher fasting blood sugar (closer to the diabetic threshold), that rate jumps to about 5.6% per year. In practical terms, that means a person with prediabetes can cross into diabetes within just a couple of years if nothing changes.
Lifestyle Plays a Bigger Role Than Genetics
Researchers have identified dozens of genetic variants linked to type 2 diabetes, but those common variants explain only a small proportion of who actually gets the disease. The much bigger factor is how you live. Large-scale studies tracking hundreds of thousands of people over decades have concluded that more than 90% of type 2 diabetes cases are potentially preventable through five habits: eating a balanced diet, maintaining a BMI of 25 or lower, exercising at least 30 minutes a day, not smoking, and drinking alcohol only in moderation.
That statistic cuts both ways. It means type 2 diabetes is very easy to develop if you carry extra weight, eat poorly, and don’t move much. It also means the condition is remarkably preventable for most people. The problem is that modern life makes the risk factors extremely common. Sedentary jobs, processed food, and chronic stress push millions of people toward insulin resistance without any single dramatic event.
Prediabetes Can Be Reversed
If you catch the process early, the trajectory isn’t locked in. In clinical trials testing structured lifestyle changes (better diet, more physical activity, modest weight loss), about 62% of people with prediabetes returned to normal blood sugar levels within two years. Even without a formal program, about 37% reversed their prediabetes on their own. The number needed to treat was just six, meaning for every six people who made lifestyle changes, one additional person avoided diabetes compared to doing nothing.
People with impaired fasting glucose responded especially well, with dramatically higher odds of reversal. Those who were already obese had somewhat lower remission rates, but still benefited. The key takeaway is that prediabetes is not a one-way street, but the window to act narrows over time as insulin-producing cells continue to deteriorate.
Type 1 Diabetes Is Different
Type 1 diabetes isn’t caused by lifestyle. It’s an autoimmune disease where the immune system attacks and destroys the insulin-producing cells in the pancreas. You can’t prevent it, and it’s not triggered by diet or exercise habits.
The exact cause remains unknown, but the leading theory is that a viral infection triggers the immune attack in people who are genetically susceptible. Enteroviruses are the strongest candidates. Researchers have found enterovirus proteins in the pancreatic tissue of 60% of people with recently diagnosed type 1, compared to just 6% of people without diabetes. Congenital rubella causes type 1 in 12% to 20% of affected children. COVID-19 infection also appears to increase the risk in children, with a 32% spike in type 1 diagnoses observed during 2021 and 2022 in one long-running study.
Other environmental factors play smaller roles. Longer breastfeeding and later introduction of gluten and cow’s milk in infancy are associated with reduced risk. The gut microbiome also appears to contribute, though the exact mechanisms are still being studied. Type 1 most commonly appears in childhood, with the majority of diagnoses occurring between ages 5 and 14, though it can develop at any age.
Gestational Diabetes Affects More Pregnancies Than You’d Expect
Between 5% and 9% of U.S. pregnancies involve gestational diabetes each year. It usually produces no noticeable symptoms, which is why routine glucose screening is standard during pregnancy. What many people don’t realize is that gestational diabetes is a strong predictor of future risk: about half of women who develop it will go on to develop type 2 diabetes later in life.
How Blood Sugar Levels Are Classified
Diabetes is diagnosed primarily through a blood test called HbA1c, which reflects your average blood sugar over the past two to three months. The ranges are straightforward:
- Normal: A1c below 5.7%
- Prediabetes: A1c between 5.7% and 6.4%
- Diabetes: A1c of 6.5% or higher
The gap between normal and diabetes is narrower than it looks. An A1c of 5.7% can creep to 6.5% over just a few years without any warning signs. Because symptoms develop so slowly, or not at all, the only reliable way to catch the progression early is through routine blood work. This is especially important if you carry extra weight, have a family history of diabetes, or have had gestational diabetes.