Yes, heart risk begins to rise before blood sugar reaches the diabetes range. The increase is modest: in large studies, people with prediabetes have roughly 15% more cardiovascular disease than people with normal blood sugar. It is a warning sign, not a diagnosis of heart disease.
Prediabetes is also the stage where the direction can still change. Structured lifestyle programs have cut the rate of progression to diabetes by more than half. Whether that also lowers heart attacks and strokes is less settled, and this article is candid about that.
Key takeaways
- Prediabetes is tied to a small but real rise in heart disease, stroke and death from any cause.
- The added risk is far smaller than the one seen with type 2 diabetes.
- Lifestyle programs clearly delay or prevent diabetes, with benefits still visible two decades later.
- Trials disagree on whether preventing diabetes also prevents heart events, so the other risk factors still need attention.
What prediabetes means
Prediabetes means your blood sugar is above the normal range but below the level used to diagnose diabetes. It is found on a blood test: an A1c, a fasting glucose or a glucose tolerance test. It causes no symptoms, so most people learn about it from routine bloodwork.
The exact cutoffs are covered in our guide to A1c and heart disease risk. The usual underlying cause is insulin resistance, which has its own page on this site.
How much higher is the risk?
A 2020 analysis in the BMJ combined 129 studies covering more than 10 million people. Over a median follow-up of 9.8 years, prediabetes was associated with a 13% higher risk of death from any cause, a 15% higher risk of cardiovascular disease, a 16% higher risk of coronary heart disease and a 14% higher risk of stroke.1
In absolute terms the difference was small: about nine extra cases of cardiovascular disease for every 10,000 people followed for a year. The link was stronger in people who already had artery disease, where prediabetes went with a 37% higher risk of further cardiovascular problems.1
For comparison, diabetes itself is linked to about twice the risk of coronary heart disease.2 Our guide to diabetes and heart disease risk covers that stage. Prediabetes sits well below it, which is the reason to act while you are still there.
Why risk rises this early
Blood sugar in the prediabetes range rarely travels alone. It tends to appear together with a larger waist, higher blood pressure, higher triglycerides and lower HDL cholesterol. Each of those is a heart risk factor in its own right.
That is why the modest numbers above should not be read as "only the sugar matters a little." A prediabetes result is often the first visible sign of a wider metabolic pattern, and the pattern as a whole is what affects your arteries.
What is reversible
The strongest evidence comes from the US Diabetes Prevention Program. It enrolled 3,234 adults with raised blood sugar who did not yet have diabetes and assigned them to a lifestyle program, a glucose-lowering medication or a placebo. The lifestyle program aimed for at least a 7% weight loss and at least 150 minutes of physical activity a week.
After an average of 2.8 years, the lifestyle program had reduced new cases of diabetes by 58% compared with placebo, and the medication had reduced them by 31%.3
The effect lasted. When the same participants were followed for about 21 years, the rate of diabetes was still 24% lower in the original lifestyle group and 17% lower in the original medication group than in the placebo group.4 The researchers noted that most of this advantage was earned in the first few years.
So progression to diabetes is not inevitable, and the changes that slow it are well defined.
What has not been shown
Preventing diabetes and preventing heart attacks are not the same result, and here the evidence is mixed.
In the 21-year follow-up of the Diabetes Prevention Program, neither the lifestyle program nor the medication reduced major cardiovascular events, defined as heart attack, stroke or cardiovascular death.5 The authors pointed out that all groups were later offered lifestyle classes and that many participants were taking statins and blood pressure medication, which may have diluted any difference.
A smaller trial in Da Qing, China, reached a different result. It followed 577 adults with impaired glucose tolerance for up to 30 years after a six-year diet and exercise program. The intervention group had 26% fewer cardiovascular events and fewer cardiovascular deaths than the control group.6
The fair summary: lifestyle change reliably delays diabetes, and it may lower heart events over the long term, but that second benefit has not been confirmed consistently. Blood pressure, cholesterol and smoking still need to be handled directly.
What gets checked
- Blood sugar, repeated over time. A single borderline result is usually confirmed and then tracked.
- Blood pressure. It often rises alongside blood sugar.
- A lipid panel. Triglycerides and HDL cholesterol are the values that most often shift.
- Waist measurement. It says more about metabolic risk than weight alone.
- An overall risk estimate. Your clinician can combine these into a 10-year figure.
How often to repeat these depends on your results and your other risk factors. That schedule is set with your clinician.
Your next step
If you have been told you have prediabetes, ask for the rest of the picture: blood pressure, lipids and an overall risk estimate. Our guide to a heart disease risk assessment explains what a fuller preventive evaluation covers.
You can also answer the three quick questions in the screener on the Cardio Res-Q program page. Insulin resistance is among the risk factors listed on that page.
Are You a Candidate for Cardio Res-Q?
Three quick questions about the risk factors we screen for. Your answers stay between you and the clinic.
Frequently asked questions
Does prediabetes always turn into diabetes?
No. In the placebo group of the Diabetes Prevention Program, about 11 of every 100 participants developed diabetes each year, which means most did not in any given year. With the lifestyle program the rate fell to about 5 per 100.
Is prediabetes dangerous for my heart right now?
The added risk is small for most people. Pooled studies put it at roughly 15% above normal, compared with about double for diabetes. It matters more as a signal to check blood pressure, cholesterol and waist size, which often change at the same time.
If I lower my blood sugar, will I avoid a heart attack?
That has not been proven. Lifestyle programs clearly reduce progression to diabetes, but the largest US trial did not find fewer heart attacks or strokes after 21 years, while a smaller Chinese trial did after 30 years. Managing all of your risk factors together is the approach the evidence supports.
Do I need medication for prediabetes?
That is a decision for you and your prescriber, and this article does not recommend for or against it. In the main US trial the lifestyle program worked better than the medication for preventing diabetes. Do not start, stop or change a medication without your prescriber.
Related reading
This article is for general education and is not medical advice. Decisions about testing and medication should be made with your clinician. If you have chest pain or other symptoms of a heart attack, call 911.
