Diabetes has long been diagnosed by measuring glucose in urine since the mid-1800s, and in blood since 1965. Current blood glucose charts categorize blood glucose levels as normal, prediabetic, or diabetic, a scale that also indicates an increased risk of heart disease. But this scale may need to be reconsidered.
Research has shown that when blood sugar levels fall just below pre-diabetes, or above “normal” levels, the risk of cardiovascular disease increases significantly.
“Being classified as ‘normal’ can have implications on cognitive function,” says Greg Fonarow, MD, professor of cardiology at the David Geffen School of Medicine at UCLA . “There was a significant difference between the upper and lower limits of the normal range. This doesn’t get as much attention as you might think.”
He and co-author Moein Ebrahimi, MD, PhD, reviewed 20 years of research in an editorial in the American Journal of Cardiology (link is external) . They highlighted a 2012 study (link is external) by Israeli researchers that found that people with fasting blood glucose levels of 95 to 99 mg/dL had twice the risk of cardiovascular disease compared with those with levels below 80 mg/dL. A 2019 study ( link is external) by researchers in Denmark and Michigan found that greater variability in “normal” HbA1c levels (average blood glucose levels over a three-month period) was associated with higher risk.
Taking these findings together, Dr. Fonarow and Dr. Ebrahimi proposed revising the classification of stages 1 to 4 by subdividing the normal range into low and high blood glucose levels and adding the associated cardiovascular risk.
The first step is to “take proactive steps to reduce that risk,” says Dr. Fonarow. This includes changes in diet, exercise, sleep quality, healthy weight and medications made during prediabetes to prevent diabetes.
risk assessment
75-80% of deaths in people with diabetes are due to cardiovascular disease, which includes premature heart attack, premature ischemic stroke, and heart failure.
Research has shown that even normal blood sugar levels can put you at risk for cardiovascular disease, but it’s not clear exactly why.
Studies in people without diabetes have shown that higher-than-normal blood glucose levels are associated with increased heart rate variability and arterial stiffening (which can lead to changes in blood pressure and blood flow).
Another possibility is fluctuations in blood sugar, or glucose levels. The greater the fluctuations, the harder it is for your body to tolerate them.
A graph showing pathways that may be involved in increased risk of cardiovascular disease when blood sugar levels are elevated but still within the normal range. (Ebrahimi, Fonarow, American Journal of Cardiology May 2025)
In 2021 A study published in the journal Blood Pressure Monitoring (External link) showed that changes in blood glucose levels are associated with blood pressure fluctuations in people with normal blood pressure. Furthermore, changes in blood glucose levels are associated with mood disorders and are a potential risk factor for heart disease.
When counseling patients, Dr. Fonarow , director of the Ahmanson-UCLA Cardiomyopathy Center and co-director of the UCLA Preventive Cardiometabolic and Cardiovascular Health Program , explains that they are at high risk: For patients with higher than normal blood sugar, other factors such as blood pressure, cholesterol, triglyceride levels, family history, age and physical activity must be considered.
For example, patients whose blood pressure is also within a safe range “need to be more aggressive in managing their lipids and blood pressure,” Dr. Fonarow said.
Risk Reversal
Screening and awareness – what Dr. Fonarow describes as “actionable data” – allow clinicians and patients to work together to make lifestyle changes that reduce both blood glucose levels and the associated cardiovascular risk.
“I’ve had patients who I’ve talked to about walking 70,000 to 10,000 steps a day and improving their diet to lose weight, ” he says. “Within three months, their fasting blood sugar levels improved and were no longer at the upper end of the normal range.”
Digital devices such as activity trackers and continuous glucose monitors can also help you track your progress, but Dr Fonarow advises using them with caution.
“Some data-driven, motivated people want to track changes in their diet and their reactions to individual foods and get feedback,” he says, “so this data has been very helpful for some patients.”
Other UCLA health care resources include:
- The UCLA Barbra Streisand Women’s Heart Health Program provides clinical care and community outreach programs.
- The Diabetes Prevention Program (DPP) emphasizes increased physical activity and healthier food choices.
- UCLA’s Fit for Health program provides children and adolescents with instruction on healthy eating, physical activity and psychosocial wellness to prevent and manage overweight and obesity.
“Most cardiovascular disease is preventable,” says Dr. Fonarow, and much of it reflects lifestyle changes and managing each individual’s risk within their control.”
