How diabetes cause kidney failure?



QUESTION:


How does diabetes cause kidney failure?




Quick Answer


Over many years, high blood glucose can damage the kidneys’ tiny blood vessels and filtering units, called glomeruli. The filters may first leak albumin into the urine and later become scarred, causing the estimated glomerular filtration rate, or eGFR, to decline. High blood pressure, smoking and cardiovascular disease can accelerate this damage. Early diabetic kidney disease usually has no symptoms, so yearly urine albumin and blood kidney-function tests are essential.



Answer by Dr. Albana Greca, MD, MMedSc


Hello,


Diabetes usually damages kidneys gradually. Early detection and treatment can often slow or prevent progression.


How Healthy Kidneys Filter Blood


Each kidney contains microscopic filtering units called nephrons. Their glomeruli remove waste and extra fluid while retaining blood cells and proteins such as albumin.


Kidneys also regulate blood pressure, minerals, acid balance, red-cell production and vitamin D activation.


What High Blood Sugar Does to the Kidney


Chronic hyperglycemia changes glomerular blood flow and pressure. Early hyperfiltration and continued metabolic stress damage the filters and surrounding tissue.


As the filters become damaged:



  • Albumin begins leaking into the urine.

  • Inflammation and abnormal tissue growth develop.

  • Some filtering units become scarred and stop working.

  • The remaining nephrons work harder, creating additional stress.

  • Kidney filtration gradually declines and waste accumulates.


This is diabetic kidney disease or diabetic nephropathy. It is more complex than small-artery atherosclerosis and is not caused only by cholesterol or fatty acids.


Our overview of diabetes and kidney disease explains the stages, testing and treatment in more detail.


Why High Blood Pressure Matters


High blood pressure damages the same filters and often accompanies diabetes. Smoking, high cholesterol, obesity, heart disease, family history and longer diabetes duration add risk.


Protecting the kidneys therefore requires more than lowering glucose. Blood pressure, cholesterol, smoking and cardiovascular risk also need attention.


Early Kidney Disease Often Has No Symptoms


Reduced urine, anemia or eyelid swelling are not reliable early warnings. Most people feel normal, and urine volume may remain normal despite damage.


Anemia, reduced urine, swelling, nausea, itching, poor appetite, breathlessness and severe fatigue usually appear later or have another cause.



Key message: A person with diabetes can have kidney disease while feeling completely well. Blood and urine testing—not symptoms—is the reliable way to detect it early.



The Two Essential Kidney Tests


1. Urine albumin-to-creatinine ratio (UACR): This detects albumin leakage. A result of 30 mg/g or higher may indicate damage, but temporary elevations should usually be confirmed.


2. Estimated glomerular filtration rate (eGFR): Calculated from blood creatinine, it estimates filtration. Persistent eGFR below 60 may indicate CKD even with normal urine albumin.


CKD may involve albuminuria, reduced eGFR or both. Abnormalities generally must persist for at least three months.


Who Should Be Screened?



  • Type 2 diabetes: Check UACR and eGFR from the time of diagnosis and at least yearly.

  • Type 1 diabetes: Begin yearly screening after approximately five years of diabetes.

  • Existing kidney disease: Test more often according to the degree of albuminuria, eGFR decline and treatment changes.


A normal serum creatinine alone does not fully exclude early kidney disease. Ask for the actual eGFR and UACR values and track how they change over time.


How Kidney Failure Develops


As nephrons are lost, kidneys cannot remove waste or balance fluid, acid and minerals. Fluid overload, high potassium, acidosis, anemia and bone problems may follow.


Kidney failure is very advanced loss of function, often eGFR below 15 or symptoms requiring dialysis or transplantation. Progression is not inevitable.


How Progression Can Be Slowed



  • Manage glucose: Work toward an individualized HbA1c target without causing severe hypoglycemia.

  • Control blood pressure: The target and medicines should be individualized.

  • Use kidney-protective medication when indicated: ACE inhibitors or ARBs are commonly used for hypertension with albuminuria.

  • Consider an SGLT2 inhibitor: In suitable people with type 2 diabetes and CKD, these medicines can slow kidney decline and reduce heart-failure risk.

  • Consider additional therapy: A clinician may use finerenone or a GLP-1 receptor agonist in selected patients.

  • Stop smoking and manage cholesterol.

  • Limit excess sodium: A kidney diet should be individualized, especially when potassium or phosphorus is abnormal.

  • Avoid unnecessary kidney injury from dehydration and inappropriate use of NSAID painkillers such as ibuprofen or naproxen.


Do not start, stop or combine kidney-protective drugs without medical supervision. ACE inhibitors and ARBs require kidney-function and potassium monitoring, and they should not routinely be used together.


See our guides to controlling diabetes safely, understanding HbA1c and preventing diabetes complications.


When to Seek Prompt Medical Care



Seek prompt or emergency care for a major reduction in urine, rapidly increasing swelling, severe shortness of breath, persistent vomiting, confusion, chest pain, extreme weakness, or suspected severe dehydration. These symptoms may indicate acute kidney injury, advanced kidney disease or another serious condition.



Falling eGFR, rising albuminuria, blood in urine, uncertain cause or resistant blood pressure may require nephrology referral.


This educational answer does not replace individualized kidney testing, diagnosis or treatment from a diabetes clinician or kidney specialist.


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