Prediabetes is often described as a warning stage before type 2 diabetes, but that description can be misleading. It is better understood as a state in which blood glucose is higher than the normal range but has not reached the diagnostic threshold for diabetes.
The important point is that many people with prediabetes do not feel different.
The Centers for Disease Control and Prevention (CDC) estimates that more than 1 in 3 U.S. adults have prediabetes and that most do not know they have it.
That makes blood testing particularly important. A person can feel healthy, remain physically active, and have no obvious symptoms while blood glucose regulation is gradually changing.
Prediabetes means blood glucose levels are elevated but not high enough to meet the diagnostic criteria for diabetes.
According to the American Diabetes Association (ADA), prediabetes can be identified using one of several standard tests:
A1C: 5.7%–6.4%
Fasting plasma glucose: 100–125 mg/dL
2-hour plasma glucose during an oral glucose tolerance test: 140–199 mg/dL
Diabetes begins at higher thresholds.
These ranges are diagnostic criteria—not a prediction that someone will definitely develop diabetes.
The A1C test is particularly useful because it provides an estimate of average blood glucose over approximately the previous two to three months.
Unlike a fasting glucose test, it does not require the patient to fast.
An A1C result can therefore provide a broader view of glucose exposure rather than measuring blood sugar at one specific moment.
Consider someone whose A1C changes from:
5.4% → 5.6% → 5.8%
The first two results are below the ADA's prediabetes threshold, while the third falls within the prediabetes range.
The progression is important because it shows a change in glucose regulation over time, not simply one isolated result.
A clinician would interpret that trend alongside other factors rather than relying on the number alone.
Fasting plasma glucose measures blood sugar after an overnight fast.
The ADA defines:
|
Fasting glucose |
Interpretation |
|
Below 100 mg/dL |
Normal range |
|
100–125 mg/dL |
Prediabetes range |
|
126 mg/dL or higher |
Diabetes range* |
*Diabetes diagnosis generally requires confirmation unless there are unequivocal symptoms or other diagnostic circumstances.
Fasting glucose can fluctuate because of factors such as:
Illness
Stress
Sleep
Medications
Recent dietary patterns
Biological variation
That is why one result should be interpreted in context.
Blood glucose often rises gradually.
The body can compensate for worsening insulin resistance for a period of time by producing more insulin. During this stage, glucose levels may be elevated without producing noticeable symptoms.
This is one reason prediabetes can remain undetected.
The CDC specifically notes that prediabetes often has no clear symptoms, making screening particularly important for people with relevant risk factors.
Prediabetes often occurs alongside other cardiometabolic risk factors.
These may include:
Increased waist circumference
Elevated blood pressure
Abnormal cholesterol levels
Physical inactivity
Excess body weight
Family history of diabetes
The American Heart Association includes blood glucose, blood pressure, cholesterol, weight, physical activity, diet, sleep, and tobacco exposure within its broader framework for cardiovascular health.
This matters because glucose regulation and cardiovascular health are closely connected.
One of the underlying processes associated with prediabetes is insulin resistance.
Insulin helps move glucose from the bloodstream into cells where it can be used for energy.
When cells become less responsive to insulin, the body may compensate by producing more insulin.
For a time, blood glucose may remain relatively controlled.
Eventually, however, the body's ability to compensate may become insufficient, allowing glucose levels to rise further.
Not everyone with insulin resistance will progress to diabetes, but recognizing metabolic risk earlier creates an opportunity to address modifiable factors.
Excess body weight is an important risk factor for prediabetes, but body weight alone does not determine who develops abnormal glucose regulation.
Other factors include:
Family history
Age
Physical activity
Ethnicity and genetics
Previous gestational diabetes
Certain medications
Other metabolic conditions
The CDC recommends diabetes screening based on age and risk factors rather than relying on symptoms alone.
This is why someone who appears lean or physically active should not automatically assume their glucose regulation is perfect.
Prediabetes does not mean that diabetes is inevitable.
The CDC's National Diabetes Prevention Program is built around evidence that lifestyle intervention can substantially reduce the risk of progression to type 2 diabetes in people at high risk.
Areas commonly addressed include:
Physical activity
Nutrition
Weight management when appropriate
Sleep
Other cardiovascular risk factors
The objective is not simply to make one laboratory value look better. It is to improve the broader metabolic environment.
The CDC recommends that adults generally aim for at least 150 minutes of moderate-intensity physical activity per week, with muscle-strengthening activity also incorporated into the week.
For someone with prediabetes, increasing physical activity can improve insulin sensitivity and glucose regulation.
Importantly, activity does not have to mean intensive gym training.
Walking, cycling, swimming, strength training, and other activities can contribute.
The appropriate starting point depends on a person's current fitness, health conditions, and physical limitations.
Skeletal muscle is a major site of glucose disposal.
When muscles contract during physical activity, they can take up glucose from the bloodstream through pathways that are not entirely dependent on insulin.
This helps explain why maintaining muscle mass and regularly using those muscles can be relevant to metabolic health.
For adults, particularly as they age, preserving strength and physical activity can therefore support more than mobility—it can also contribute to healthy glucose regulation.
Prediabetes is not solely a future diabetes concern.
Elevated blood glucose often occurs alongside other cardiovascular risk factors, and people with abnormal glucose regulation may have an increased risk of cardiovascular disease.
The American Heart Association emphasizes the connection between diabetes, metabolic health, and cardiovascular disease and identifies blood glucose as one of its core measures of cardiovascular health.
This makes a prediabetes result an opportunity to look at the whole cardiometabolic picture, rather than focusing only on diabetes.
The appropriate timing of screening depends on age, weight, family history, and other risk factors.
The USPSTF currently recommends screening adults 35 to 70 years old who have overweight or obesity for prediabetes and type 2 diabetes.
The ADA uses broader risk-based screening criteria and recommends testing adults with certain risk factors, with additional guidance based on age and individual circumstances.
People should therefore discuss screening with their healthcare provider rather than relying solely on whether they have symptoms.
This is where trends can become particularly useful.
A result of:
5.6% A1C
does not meet the ADA's prediabetes threshold.
But if previous results were:
5.1% → 5.3% → 5.6%
the direction of change may still be worth discussing.
This does not mean that prediabetes is present.
It means that the trajectory may provide useful context when combined with weight, activity, blood pressure, family history, and other health information.
Preventive care is not only about identifying disease after a threshold has been crossed.
A glucose or A1C result does not provide a complete assessment of metabolic health.
It does not directly measure:
Muscle mass
Body-fat distribution
Fitness
Insulin levels in routine clinical practice
Sleep quality
Physical activity
Dietary quality
These factors can influence metabolic health and may be relevant when interpreting a glucose result.
This is why a comprehensive evaluation considers laboratory results alongside clinical history and lifestyle.
Prediabetes itself often causes no obvious symptoms.
As blood glucose becomes significantly elevated, however, symptoms may include:
Increased thirst
Frequent urination
Unexplained weight loss
Fatigue
Blurred vision
These symptoms should be evaluated rather than assumed to be related to lifestyle or aging.
Blood glucose is not a static measurement.
It can change with:
Age + Activity + Body Composition + Sleep + Nutrition + Medications + Genetics + Other Health Conditions
This is why comparing current results with previous results can sometimes provide more useful information than looking at today's number in isolation.
A laboratory result is a snapshot.
A series of results can show a trajectory.
Prediabetes often develops quietly, which is why relying on symptoms alone can miss an important change in metabolic health.
A1C, fasting glucose, and—when appropriate—an oral glucose tolerance test can identify abnormal glucose regulation before diabetes is diagnosed.
But the most useful interpretation goes beyond the number.
Consider:
What is the current result?
How has it changed over time?
Are other metabolic risk factors changing?
What does the result mean in the context of the person's overall health?
Prediabetes is not a guarantee that diabetes will develop. It is a measurable signal that glucose regulation deserves attention—and, for many people, an opportunity to address risk before more significant metabolic disease develops.
