What are the complications of prediabetes if it’s left untreated?

Prediabetes might not cause obvious symptoms, but it is not harmless. When blood glucose levels stay above normal for years, damage can begin to build up in blood vessels and organs — even before type 2 diabetes is formally diagnosed.

This article explains what can happen if prediabetes is left untreated, the types of complications to be aware of, and how early action can dramatically reduce your risk.

Why Prediabetes Matters

People with ongoing high blood glucose levels have a higher risk of:

• Heart attacks and strokes
• Vision problems
• Nerve damage and foot problems
• Kidney disease
• Mood problems such as anxiety and depression

Some of these risks start to rise even when glucose levels are only in the prediabetes range. The good news is that early diagnosis and effective treatment can substantially reduce these risks.

Metabolic Syndrome

Prediabetes often occurs as part of metabolic syndrome: a cluster of conditions that includes:

• Insulin resistance
• Central obesity (fat around the waist)
• High blood pressure
• Abnormal cholesterol and triglycerides

People with metabolic syndrome are more likely to develop type 2 diabetes and cardiovascular disease. You can learn more about your overall risk using the Diabetes Risk Calculator.

Macrovascular Complications – Large Blood Vessels

Macrovascular disease affects the larger blood vessels supplying the heart, brain, and legs.

Coronary Artery Disease (Heart Disease)

Fatty deposits (atherosclerosis) can build up in coronary arteries, narrowing them and increasing the risk of heart attacks. People with prediabetes and diabetes have a higher risk of:

• Chest pain with exertion
• Heart attacks
• Heart failure

Stroke (Cerebrovascular Disease)

Similar fatty deposits can affect the arteries supplying the brain. If a vessel becomes blocked or ruptures, a stroke can occur. Remember the FAST warning signs:

• Face – drooping on one side?
• Arms – weakness in one arm?
• Speech – slurred or strange?
• Time – call emergency services immediately.

Peripheral Artery Disease (PAD)

Poor circulation in the legs can cause pain when walking (claudication), slow healing, and in severe cases, ulcers and amputation.

Microvascular Complications – Small Blood Vessels

Microvascular damage affects small blood vessels supplying the eyes, kidneys, and nerves. These complications are more strongly associated with type 2 diabetes, but risk begins to rise in prediabetes, especially when other risk factors are present.

Retinopathy (Eye Disease)

High glucose can damage the tiny blood vessels at the back of the eye (retina), leading to bleeding, scarring, and vision loss if left untreated.

Nephropathy (Kidney Disease)

Kidneys filter waste products from the blood. Damage to kidney blood vessels can eventually lead to protein leakage in the urine and, in severe cases, kidney failure.

Neuropathy (Nerve Damage)

Nerve damage can cause numbness, burning, tingling, or pain — particularly in the feet. Loss of sensation increases the risk of unnoticed injuries and ulcers.

Other Related Health Issues

Prediabetes is also linked with:

• Fatty liver disease
• Sleep apnoea
• Gum disease
• Mood problems such as depression and anxiety

You can read more about the emotional impact here: Prediabetes and mental health

Can Complications Be Prevented?

Yes. The earlier you act, the more you can reduce your risk. Key steps include:

• Improving diet quality and stabilising blood glucose
• Losing even a modest amount of weight if you carry extra weight around your middle
• Increasing physical activity
• Treating blood pressure and cholesterol if needed
• Stopping smoking

For more detail, see: Preventing prediabetes and borderline diabetes

What Should You Do Next?

If you have prediabetes, talk with your doctor about:

• How often to have blood tests and blood pressure checks
• Whether you need eye and kidney checks
• Support for lifestyle changes or medication if appropriate

To understand how prediabetes, insulin resistance, and complications fit together — and what you can do about it — you can join the free, doctor-led webinar:

Join the Prediabetes & Insulin Resistance Masterclass →

To receive reminders and practical prevention strategies by email: Click here to receive prediabetes prevention emails.