In medicine, some of the most important discoveries happen by surprise. A medication developed for one purpose reveals unexpected benefits elsewhere — and changes the way entire conditions are managed. SGLT2 inhibitors are a compelling example of exactly that.

Originally designed to lower blood sugar in people with type 2 diabetes, these medicines have become one of the most exciting advances in heart care in recent years. Large international trials have shown that they meaningfully reduce hospital admissions for heart failure, protect the kidneys, and improve survival — in patients with and without diabetes.

Today, SGLT2 inhibitors are increasingly prescribed not just for diabetes, but as a cornerstone treatment for heart failure and kidney disease.

How Do They Work?

The kidneys normally filter glucose out of the blood but then reabsorb most of it back in. SGLT2 inhibitors block this reabsorption — so excess glucose leaves the body in the urine instead. In people with diabetes, this lowers blood sugar. That was the intended effect.

But something else was happening too. By changing how the kidneys handle glucose and sodium, these medicines also reduce fluid build-up in the body, lower blood pressure slightly, and reduce the workload on the heart. They also appear to have direct protective effects on heart muscle cells and may improve the way the heart uses energy. The full picture is still being studied — but the benefits are clear and consistent.

What began as a diabetes medication has become one of the most important tools in modern heart failure management — a reminder that in medicine, the most valuable discoveries are sometimes the ones we did not set out to make.

Which Medicines Belong to This Group?

Several medicines belong to the SGLT2 inhibitor family. The most widely used in heart failure are empagliflozin and dapagliflozin. Your cardiologist will advise which is most appropriate based on your individual situation.

You Do Not Need to Have Diabetes to Benefit

This is one of the most important points about SGLT2 inhibitors — and one that many patients do not realise.

When patients are told they are being prescribed a “diabetes medication” for their heart failure, it can cause confusion. They may worry about their blood sugar dropping dangerously low, or wonder if there has been a mistake. There has not. In people without diabetes, SGLT2 inhibitors do not cause dangerous drops in blood sugar — the blood-sugar-lowering effect is far less pronounced when glucose levels are already normal.

The heart failure benefits are entirely separate from the diabetes benefits — and they apply regardless of whether you have diabetes or not.

What Does the Evidence Show?

For heart failure with reduced pumping function

The DAPA-HF trial studied dapagliflozin in nearly 5,000 patients with heart failure where the heart’s pumping function was reduced. The results showed a meaningful reduction in hospital admissions for heart failure and cardiovascular death — in patients both with and without diabetes. The EMPEROR-Reduced trial confirmed exactly the same findings for empagliflozin.

For heart failure with preserved pumping function

Until recently, heart failure where the heart squeezes normally but cannot relax properly had very few proven treatments. SGLT2 inhibitors have changed that. The EMPEROR-Preserved and DELIVER trials both showed meaningful reductions in hospital admissions and improvements in quality of life in this group — making these the first medicines to show consistent benefit across both main types of heart failure.

In acute heart failure and after a heart attack

The evidence has now extended beyond stable, long-term heart failure. Starting SGLT2 inhibitors early — during or shortly after a hospital admission for heart failure — appears safe and beneficial. In patients who have had a heart attack, early use alongside standard medicines appears safe and adds further benefit on top of existing treatment.

Benefits Beyond the Heart — Kidney Protection

The heart and kidneys are closely linked — when one is under strain, the other often is too. SGLT2 inhibitors appear to benefit both simultaneously. They have been shown to slow the progression of kidney disease, reduce pressure within the kidney’s tiny filtering units, and improve long-term kidney outcomes. For patients dealing with both heart failure and kidney disease, this dual benefit makes them particularly valuable.

Side Effects — What to Be Aware Of

Most patients tolerate SGLT2 inhibitors well. Here is what to know:

When to Temporarily Stop — Sick Day Rules

There are certain situations where your doctor may advise pausing SGLT2 inhibitors temporarily — before planned surgery, during periods of prolonged fasting, or if you become significantly unwell with vomiting, diarrhoea, or dehydration. This reduces the small but real risk of the body producing excess acid during times of physical stress.

Ask your doctor or specialist about sick day rules — a simple set of guidelines about when to pause and when to safely restart your medication. If you have not had this conversation yet, it is worth raising at your next appointment.

Conclusion

SGLT2 inhibitors are one of the most significant advances in heart care in recent years. They started as diabetes medicines and turned out to be something much more important — a class of drugs that meaningfully improves outcomes for people with heart failure, protects the kidneys, and benefits patients regardless of whether they have diabetes.

The evidence is strong, the guidelines have been updated, and the clinical impact is real. If you have heart failure and are not currently taking one of these medicines, it is worth raising at your next appointment and asking whether an SGLT2 inhibitor has a role in your treatment.

More from Heart Matters

• Heart Failure and Quadruple Therapy — The Four Pillars of Treatment
• Recovering After a Heart Attack
• Coronary Artery Disease — Heart Matters Dedicated Resource
• Understanding Your Cardiovascular Risk Factors