Is Good Blood Sugar Control Enough to Protect Your Kidneys? — The Overlooked Role of Blood Pressure in Diabetes

Why Does Kidney Function Decline Even When Blood Sugar Is Well Controlled?

People with diabetes who have focused on managing their blood sugar may sometimes hear unexpected news during a medical checkup:

“Your HbA1c is fairly well controlled, but your kidney function is gradually declining.”

This can leave patients wondering why their kidneys are getting worse despite their efforts to manage their blood sugar.

According to Seoul National University Hospital Medical Information, diabetic nephropathy develops in approximately 30% of people with type 2 diabetes and generally begins around 10 years after the onset of diabetes.

Blood sugar control is essential, but it may not be enough on its own. Blood pressure is also considered an important factor in the progression of diabetic kidney disease.

In this article, we will examine how blood pressure affects diabetic nephropathy and summarize the management recommendations in current clinical guidelines.

How Does Blood Pressure Damage the Kidneys?

Blood pressure is particularly important in diabetic nephropathy because the kidneys contain millions of tiny blood vessels that filter the blood.

The glomeruli, also known as renal glomeruli, are networks of tiny capillaries that filter waste and excess fluid from the blood. When blood sugar remains high, the walls of these blood vessels can gradually thicken and become damaged.

If blood pressure also remains elevated, additional pressure is placed on the already damaged glomeruli.

This increased pressure can contribute to a decline in the glomerular filtration rate (GFR) and may cause protein to leak into the urine. Proteinuria, or excess protein in the urine, is one of the early signs of kidney damage.

In other words, blood sugar and blood pressure can each affect kidney health independently, and their combined effects may further increase the burden on the kidneys.

Managing blood sugar while overlooking blood pressure may leave an important part of diabetic kidney disease prevention unaddressed.

Blood Pressure Target Recommended by Guidelines — Below 130/80 mmHg

The Korean Diabetes Association Clinical Practice Guideline for Diabetic Kidney Disease (2023) recommends a target blood pressure of below 130/80 mmHg for patients with diabetic kidney disease.

The guideline recommends lifestyle modifications when blood pressure exceeds 120/80 mmHg. Immediate pharmacological treatment is recommended when systolic blood pressure is 140 mmHg or higher, or diastolic blood pressure is 85 mmHg or higher.

The 2025 AHA/ACC Hypertension Guideline also recommends a target blood pressure below 130/80 mmHg for people with diabetes or chronic kidney disease. It reports that early and intensive blood pressure control may help slow the progression of diabetic kidney disease.

For Readers with Diabetes or Chronic Conditions

SGLT2 inhibitors are medications that provide kidney-protective benefits in addition to helping control blood sugar. The 2025 AHA/ACC guideline also recommends their use in patients with diabetes and chronic kidney disease.

In Korea, the insurance coverage for certain medications has also expanded to include kidney and cardiovascular protection.

GLP-1 receptor agonists, including semaglutide-based medications, are also supported by accumulating evidence of cardiovascular and kidney benefits.

The optimal combination of medications depends on each patient's kidney function, current medications, and overall health. Your healthcare provider should determine the most appropriate treatment plan.

Be sure to review your current prescriptions and kidney function results with your doctor during regular appointments.

For more information on the cardiovascular benefits of SGLT2 inhibitors, read this article.

What Should You Check When Managing Diabetic Kidney Disease?

Here are the key things to check when managing diabetic kidney disease, also known as diabetic nephropathy.

1. Check Your Kidney Function

Regular testing of estimated glomerular filtration rate (eGFR) and urine albumin, which helps detect albuminuria, is recommended.

Even when blood sugar is well controlled, kidney function should be monitored separately.

2. Monitor Your Blood Pressure at Home

Blood pressure may be elevated at night even when measurements taken at the hospital appear normal.

Measuring and recording your blood pressure regularly in the morning and evening can provide useful information during medical appointments.

3. Manage Your Lifestyle as a Whole

A low-sodium diet, aerobic exercise, smoking cessation, and limiting alcohol consumption may help improve both blood pressure and blood sugar control.

4. Warning Signs to Watch for When Taking SGLT2 Inhibitors

Although rare, diabetic ketoacidosis may occur in some people taking SGLT2 inhibitors. Warning signs include nausea, abdominal pain, and difficulty breathing.

Urinary tract infections, including symptoms such as painful urination and frequent urination, have also been reported in some patients.

If you experience these symptoms, contact your healthcare provider.

If you are interested in the connection between oral health and diabetes, you can also read this article.

Today's Key Takeaway — Manage Both Blood Sugar and Blood Pressure

Blood sugar control is fundamental to preventing and managing diabetic kidney disease. However, blood pressure is also an independent factor that can damage the kidneys, and the combined effects of elevated blood sugar and blood pressure may place an even greater burden on kidney health.

Current guidelines, including the 2023 Korean Diabetes Association guideline and the 2025 AHA/ACC Hypertension Guideline, recommend a target blood pressure below 130/80 mmHg for patients with diabetes or diabetic kidney disease, as applicable.

Even when your blood sugar is well controlled, it is important to monitor your blood pressure and regularly discuss the progression of diabetic kidney disease with your primary care physician, endocrinologist, or nephrologist.

References

1. Seoul National University Hospital Medical Information — Diabetic Kidney Disease
2. Korean Diabetes Association Clinical Practice Guideline for Diabetic Kidney Disease (2023), Korean Journal of Internal Medicine
3. 2025 AHA/ACC Hypertension Guideline — Implications for Diabetes and Chronic Kidney Disease (PMC)

Disclaimer: This article is intended for general informational purposes only and does not constitute medical advice. If you have symptoms or require diagnosis or treatment, please consult a qualified healthcare professional. If you are currently taking medication or undergoing treatment, discuss any changes to your diet or lifestyle with your healthcare provider beforehand.