Diabetes affects heart health by gradually damaging the lining of the blood vessels, which speeds up the build-up of fatty plaque in the arteries that supply the heart. It also tends to come with high blood pressure, raised cholesterol and extra weight, and over time it can stiffen and weaken the heart muscle itself. Together these raise the risk of heart attack, stroke and heart failure. The British Heart Foundation reports that people with diabetes are nearly twice as likely to die from heart disease or stroke as people without the condition.
The encouraging news is that much of this extra risk can be reduced. I have been a Consultant Cardiologist at Kingston Hospital NHS Trust for more than 20 years. Over that time I’ve found that the patients with diabetes who do best are rarely the ones with perfect blood sugar readings. They are the ones whose blood pressure, cholesterol and overall heart risk were identified and treated early. Below I explain how diabetes affects the heart, why the warning signs are easy to miss, and what makes the biggest difference.
Why diabetes damages the heart and blood vessels
When blood glucose runs high for months or years, it injures the endothelium, the thin inner lining of the arteries. A damaged lining becomes inflamed, and cholesterol is drawn into the artery wall more easily. This is the same process behind coronary artery disease in anyone, but diabetes accelerates it and tends to make it more widespread. It is one of the clearest examples of how several factors combine to narrow the heart arteries over many years.
Diabetes rarely acts alone. Type 2 diabetes in particular is closely linked with high blood pressure, raised triglycerides, low levels of protective HDL cholesterol and weight carried around the middle. Each of these adds strain to the heart. When several are present together, the risks multiply rather than simply add up.
Diabetes also affects the heart muscle and nerves directly. Over time the heart muscle can become stiffer, so it relaxes and fills less efficiently. The nerves that carry pain signals from the heart can also be damaged, which matters a great deal for how heart disease shows itself.
The heart conditions I see most often in patients with diabetes
From working with patients across Kingston, Wimbledon and London, three problems come up far more than any others.
Coronary artery disease. Narrowing of the heart arteries is the most common heart complication of diabetes and the main cause of heart attacks. In people with diabetes the narrowing often affects more than one artery and extends further along each vessel, which can influence the treatment options available.
Heart failure. Diabetes increases the risk of heart failure, where the heart does not pump or fill as well as it should. It can follow a heart attack, but it can also develop from years of high blood pressure or from changes in the heart muscle itself. The first sign is often breathlessness on exertion that feels out of proportion to the effort involved.
Stroke. According to the BHF, people with diabetes are twice as likely to have a stroke. Atrial fibrillation, an irregular heart rhythm that raises stroke risk, is also more common in people with diabetes, and I look for it routinely.
Why the warning signs can be easier to miss
The classic heart attack involves crushing chest pain, but diabetes can blunt that signal. The BHF explains that some people with diabetes may not feel chest pain because of nerve damage, which is why so-called silent heart attacks are more common in this group.
In my experience, the most common story is not dramatic pain but a slow decline in what someone can do. A patient who used to walk briskly for an hour now stops after twenty minutes and puts it down to age or being unfit. Others describe indigestion on exertion, unusual tiredness or breathlessness climbing stairs. In someone with diabetes, I treat any change like this as a possible heart symptom until proven otherwise.
If you have diabetes and develop chest pain, pressure or tightness that is severe or lasts more than a few minutes, call 999. Do not wait to see whether it settles.
How I assess the heart in someone with diabetes
I trained and qualified as a GP before specialising in cardiology, so I know how much good diabetes care already happens in general practice. Most patients have regular checks of HbA1c, cholesterol and kidney function. What a cardiology assessment adds is a direct look at the heart and its arteries.
ECG. I carry out a 12 lead ECG during the consultation itself. It can reveal signs of a previous heart attack that went unnoticed, or a rhythm problem such as atrial fibrillation. A normal ECG is reassuring, but it does not rule out heart disease.
Echocardiogram. An echocardiogram is an ultrasound scan of the heart that shows how well the muscle pumps and relaxes and how the valves are working. Echocardiography has been a particular focus of my career, and in patients with diabetes I pay close attention to how the heart relaxes between beats. Changes in relaxation can appear years before any symptoms.
CT coronary angiogram. This scan gives a calcium score and then images of the arteries themselves. In my experience, a CT coronary angiogram works better than an exercise ECG for many people with diabetes because it shows the arteries directly. It does not depend on symptoms or ECG changes during exercise, and both can be muted by diabetes. It also tells me whether early disease is already present, which helps me decide how firmly to treat cholesterol and blood pressure.
Where blood pressure readings are uncertain, a 24 hour monitor gives a truer picture than a single reading in clinic. Blood tests complete the assessment, because HbA1c, cholesterol and kidney function each reveal something different about heart health. You can read more about how the ECG, echocardiogram and other heart tests work on my tests page.
What makes the biggest difference
Blood pressure. Controlling high blood pressure is one of the most powerful ways to protect the heart in diabetes. I strongly encourage patients to buy their own home blood pressure monitor and take regular readings. I’ve found that a fortnight of home readings tells me more than several appointments’ worth of clinic measurements, and it helps patients see the effect of their own changes.
Cholesterol. Most adults with type 2 diabetes will be offered a statin, and for many it is the single most effective heart treatment they take. When a CT scan shows calcium in the arteries, I use it to explain why treatment matters. Patients who see the evidence for themselves are far more likely to keep taking their tablets.
Diabetes medicines with heart benefits. Some newer diabetes treatments protect the heart as well as lowering blood sugar. NICE guidance now recommends offering an SGLT2 inhibitor to people with type 2 diabetes who have established heart disease or heart failure. It also recommends considering one for those whose 10 year cardiovascular risk is above 10% (NICE NG28). Uptake has been slow. One UK analysis of GP records found that only around 15% of people on diabetes treatment were prescribed one at the time of the study. If you have diabetes and heart disease, it is worth asking whether one of these medicines is right for you.
Lifestyle. Stopping smoking, being active on most days and losing even a modest amount of weight improve blood sugar, blood pressure and cholesterol at the same time. Few other single changes do that.
Blood sugar control. Good long-term glucose control reduces damage to small blood vessels in the eyes, kidneys and nerves, and it supports heart health over time. On its own, though, it is not enough. The heart benefits most when blood pressure, cholesterol and smoking are addressed alongside it.
Pre-diabetes matters too
Heart risk begins to rise before diabetes is formally diagnosed. NHS England figures show that more than 3.6 million people in England were found to have pre-diabetes in 2023, an 18% rise on the previous year. This group is at greater risk of both type 2 diabetes and heart disease. If you have been told your blood sugar is borderline, it is a good time to check your blood pressure and cholesterol and to take up the NHS support on offer.
When to see a cardiologist
If you have diabetes, a cardiology opinion is worth considering if you notice any of the following:
- chest discomfort, tightness or unusual indigestion when you exert yourself
- breathlessness or tiredness that is new or out of proportion to what you are doing
- palpitations, dizziness or blackouts
- an abnormal ECG picked up at a routine check
- several cardiac risk factors, such as high blood pressure, raised cholesterol or a family history of heart disease, and you want a clear picture of where you stand
Any of these, and particularly chest pain, deserves proper assessment rather than reassurance alone. If you have diabetes and are concerned about your heart, please contact me, Dr Arvind Vasudeva, for a thorough assessment. I see patients at Parkside Hospital in Wimbledon, The New Victoria Hospital in Kingston, Cleveland Clinic London and Heartsure in Kingston, and you can book an appointment at whichever location suits you best.