What diabetes complications affect the kidneys? 

Diabetes is the leading cause of chronic kidney disease in the United Kingdom, often referred to in clinical settings as diabetic nephropathy. This complication occurs when prolonged high blood sugar levels cause structural and functional damage to the kidneys’ delicate filtration units. Because the kidneys are responsible for filtering waste products from the blood and maintaining the body’s fluid balance, any decline in their function can have a profound impact on overall health. In many cases, kidney damage develops slowly over several years without causing any noticeable symptoms in the early stages. This makes regular clinical screening through blood and urine tests an essential part of the annual diabetic review. Understanding how diabetes affects the kidneys is the first step in taking proactive measures to protect these vital organs and prevent the progression to kidney failure. 

What We’ll Discuss in This Article 

• The biological mechanism of damage to the glomeruli. 

• The role of albuminuria as an early indicator of kidney strain. 

• The relationship between high blood pressure and diabetic nephropathy. 

• How the Estimated Glomerular Filtration Rate (eGFR) tracks kidney function. 

• Common symptoms of advanced kidney disease in patients with diabetes. 

• Clinical strategies for protecting kidney health and slowing disease progression. 

The Mechanism of Kidney Damage (Diabetic Nephropathy) 

The primary way diabetes affects the kidneys is by damaging the glomeruli, which are the tiny clusters of blood vessels that act as the kidneys’ filtration system. When blood sugar levels are consistently high, it causes the blood vessels throughout the body to become narrower and less flexible. In the kidneys, this high glucose environment leads to the production of reactive chemicals that cause inflammation and scarring (fibrosis) of the glomerular membranes. 

As the glomeruli become scarred, they lose their ability to filter the blood effectively. This means that waste products can build up in the bloodstream, while essential substances, such as proteins, begin to leak into the urine. This process of damage is usually gradual, and the body can often compensate for a significant loss of function before an individual feels unwell. According to the NHS, maintaining blood sugar levels as close to the target range as possible is the most effective way to prevent this microscopic damage from starting or worsening. 

Albuminuria: The Early Warning Sign 

One of the first signs that diabetes is affecting the kidneys is the presence of a protein called albumin in the urine, a condition known as albuminuria or microalbuminuria. Under normal conditions, the kidneys’ filters are too small to allow large protein molecules to pass through. However, when the filters are damaged by high sugar, albumin begins to leak out of the blood and into the urine. 

This leakage is often the very first indicator of kidney strain, appearing years before any change is seen in a blood test. This is why the NICE NG28 guideline mandates an annual urine test, known as the ACR (Albumin to Creatinine Ratio) test, for everyone with diabetes. Identifying albuminuria early is critical because, at this stage, the damage is often manageable or even reversible through tighter blood sugar control and the use of specific blood pressure medications that protect the kidneys. 

The Role of High Blood Pressure 

High blood pressure (hypertension) is both a cause and a consequence of diabetes related kidney complications. The kidneys play a major role in regulating the body’s blood pressure by managing fluid levels and secreting hormones. When the kidneys are damaged by diabetes, they become less efficient at regulating these processes, which often leads to a rise in blood pressure. 

Conversely, high blood pressure puts additional physical stress on the already weakened blood vessels in the kidneys, accelerating the rate of scarring. This creates a “vicious cycle” where each condition worsens the other. For this reason, the management of kidney complications always involves strict blood pressure targets, typically below 130/80 mmHg for those with evidence of kidney damage. Medications such as ACE inhibitors or ARBs are frequently prescribed not just to lower pressure, but because they have a specific protective effect on the filtration units of the kidneys. 

Tracking Function via eGFR 

To monitor how well the kidneys are functioning, clinicians use a blood test to measure the level of creatinine, a waste product from muscle breakdown. This measurement is then used to calculate the Estimated Glomerular Filtration Rate (eGFR). The eGFR provides a numerical value that represents the percentage of kidney function remaining. A “normal” eGFR is usually considered to be above 90. 

In the UK, chronic kidney disease is categorized into five stages based on the eGFR result. As the kidneys become more affected by diabetes, the eGFR will gradually decline. If the eGFR drops below 60 for more than three months, a diagnosis of chronic kidney disease (CKD) is made. Tracking this number over several years allows your clinical team to see if your kidneys are stable or if your treatment plan needs to be adjusted to provide more protection. 

CKD Stage	eGFR Range	Clinical Meaning
Stage 1	90+	Normal function with some evidence of damage
Stage 2	60 to 89	Mildly decreased function
Stage 3	30 to 59	Moderately decreased function
Stage 4	15 to 29	Severely decreased function
Stage 5	Below 15	Kidney failure (End-stage renal disease)

Symptoms of Advanced Kidney Complications 

In the early stages, kidney complications do not usually cause any physical symptoms, which is why they are often called a “silent” complication. Symptoms typically only appear when kidney function has significantly declined, usually reaching Stage 4 or 5. At this point, the kidneys can no longer keep up with the body’s waste removal and fluid balance needs. 

Common symptoms of advanced kidney disease include: 

• Swelling in the ankles, feet, or hands (oedema) due to fluid retention. 

• Increased tiredness, lethargy, and shortness of breath. 

• Changes in urination frequency, particularly at night. 

• Persistent nausea or a loss of appetite. 

• Itchy skin or muscle cramps. 

• Foamy urine, which indicates high levels of protein leakage. 

If you notice any of these symptoms, it is important to speak with your GP or diabetes specialist immediately. While these symptoms can be caused by other conditions, they are key indicators that your kidney function may need an urgent review. 

Strategies for Protecting Kidney Health 

Protecting your kidneys is a primary focus of modern diabetes management. The most effective strategy is a combination of blood sugar and blood pressure control. In 2026, many patients with early kidney strain are prescribed a class of medications called SGLT2 inhibitors. While originally developed to lower blood sugar, these drugs have been found to significantly reduce the pressure inside the kidneys’ filters, slowing the progression of kidney disease and reducing the risk of heart failure. 

In addition to medication, lifestyle choices play a vital role. Reducing salt intake helps to manage blood pressure, while stopping smoking protects the blood vessels from further damage. Regular participation in your annual diabetic review ensures that your ACR and eGFR are monitored, allowing for early intervention if any changes occur. By working closely with your healthcare team and maintaining your targets, you can significantly reduce the risk of your kidney complications progressing to a stage where dialysis or a transplant might be needed. 

Conclusion 

Diabetes affects the kidneys primarily by damaging the tiny filtration units called glomeruli, leading to protein leakage and a decline in overall function. This process, known as diabetic nephropathy, is often silent in its early stages, making annual urine and blood tests essential for detection. High blood pressure further accelerates this damage, necessitating strict cardiovascular management. However, through a combination of blood sugar control, protective medications like SGLT2 inhibitors, and healthy lifestyle habits, the progression of kidney disease can be significantly slowed. Protecting your kidney health is a lifelong priority that ensures the continued wellbeing of your entire body. If you experience severe, sudden, or worsening symptoms, call 999 immediately. 

Authority Snapshot 

This article examines the clinical impact of diabetes on kidney function to provide patients with evidence based health guidance. It has been written by Dr. Rebecca Fernandez, a UK trained physician with an MBBS and extensive experience in cardiology, internal medicine, and emergency care. Dr. Fernandez has managed thousands of patients with chronic metabolic conditions and is dedicated to providing care that aligns strictly with the latest 2026 NHS and NICE guidance to ensure medical accuracy and patient safety.