Your Health
Borderline high blood sugar: what it means and what to do
98 million Americans have pre-diabetes and 80% don't know it. Here is what borderline blood sugar means, when to worry, and how to reverse it.
Reviewed by Sofia Sigal-Passeck, Slothwise co-founder & National Science Foundation-backed researcher
This article is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider about your blood sugar levels.
What does borderline high blood sugar mean?
Borderline high blood sugar, medically called pre-diabetes, means your blood glucose levels are higher than normal but not yet high enough for a type 2 diabetes diagnosis. Specifically, it means a fasting blood glucose between 100 and 125 mg/dL, or an A1C between 5.7% and 6.4%. A fasting glucose of 126 mg/dL or higher, or an A1C of 6.5% or higher, is diabetes.
This is extremely common. The CDC estimates that 98 million American adults have pre-diabetes, and roughly 80% of them do not know it. Most people with borderline blood sugar feel completely normal, which is why it is almost always discovered on routine blood work rather than from symptoms.
Should you worry about borderline blood sugar?
Yes and no. Pre-diabetes is not an emergency, and it does not mean you will definitely develop diabetes. But it is a warning signal that your body is starting to struggle with insulin, and it significantly increases your risk if you do nothing. Without lifestyle changes, 15-30% of people with pre-diabetes develop type 2 diabetes within 5 years. Pre-diabetes also independently raises your risk for heart disease and stroke.
The good news: pre-diabetes is one of the most reversible conditions in medicine. Research consistently shows that lifestyle changes can cut the progression rate by more than half.
What causes borderline high blood sugar?
The most common factors include:
Excess weight: Carrying extra weight, especially around the abdomen, increases insulin resistance. This is the single largest risk factor.
Physical inactivity: Sedentary lifestyles reduce the body's ability to use insulin effectively.
Family history: Having a parent or sibling with type 2 diabetes raises your risk.
Age: Risk increases after 35, and rises significantly after 45.
Diet: Diets high in refined carbohydrates, sugary drinks, and processed foods contribute to insulin resistance over time.
Other conditions: Polycystic ovary syndrome (PCOS), gestational diabetes history, and sleep apnea are all associated with higher risk.
What lifestyle changes can reverse pre-diabetes?
The landmark Diabetes Prevention Program (DPP) study showed that modest lifestyle changes reduced the risk of developing diabetes by 58%. The key interventions that work:
Lose 5-7% of body weight: For someone weighing 200 pounds, that is 10-14 pounds. This amount of weight loss has been shown to significantly improve insulin sensitivity and often returns blood sugar to normal.
Exercise 150 minutes per week: Moderate activity like brisk walking, cycling, or swimming. This does not need to be intense, just consistent.
Improve diet quality: Reduce refined carbohydrates and sugary drinks. Increase vegetables, whole grains, lean protein, and fiber. A Mediterranean-style diet has strong evidence for improving blood sugar.
Improve sleep: Poor sleep and sleep apnea worsen insulin resistance. Aim for 7-9 hours of quality sleep.
These changes are more effective than medication for preventing the progression from pre-diabetes to diabetes.
What follow-up tests will your doctor order?
If your blood sugar is borderline, your doctor will typically:
Repeat the test: A single borderline result should be confirmed with a repeat fasting glucose or A1C test
Oral glucose tolerance test (OGTT): You drink a glucose solution and have blood drawn at intervals to see how your body processes sugar. A 2-hour value of 140-199 mg/dL confirms pre-diabetes.
Assess cardiovascular risk: Because pre-diabetes is linked to heart disease, your doctor may check cholesterol, blood pressure, and other risk factors
Screen regularly: If you have pre-diabetes, blood sugar should be checked at least annually to catch any progression early
For people who want to track how their blood sugar changes over time with lifestyle modifications, tools like Slothwise can import lab results from 60,000+ hospitals and display fasting glucose and A1C trends across every test, making it easy to see whether your changes are working.
This article is for informational purposes only. If you have concerns about your blood sugar levels, please consult your healthcare provider.
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Borderline high blood sugar: what it means and what to do
98 million Americans have pre-diabetes and 80% don't know it. Here is what borderline blood sugar means, when to worry, and how to reverse it.
