Diabetes and Kidney Health

How Diabetes Damages the Kidneys: Diabetic Nephropathy Explained

The connection between diabetes and kidney health is one of the most clinically significant relationships in all of chronic disease management. Diabetes is the single leading cause of kidney failure in the United States and most developed countries, responsible for approximately 44% of all new cases of end-stage renal disease (ESRD) each year. Understanding how diabetes damages the kidneys — and what can be done to slow or prevent that damage — is essential for anyone living with Type 1 or Type 2 diabetes. Our guide on what is diabetes provides foundational context; this article focuses on the kidney-specific mechanisms, progression stages, monitoring protocols, and protective treatments.

The primary mechanism by which diabetes harms the kidneys is called diabetic nephropathy — a progressive form of kidney disease driven directly by chronically elevated blood glucose. The kidneys filter blood through approximately one million microscopic units called glomeruli, each consisting of a tiny knot of capillaries enclosed in a structure called Bowman’s capsule. These glomerular capillaries perform the critical work of filtering waste products and excess fluid out of the blood while retaining proteins and blood cells that the body needs. Chronically elevated blood glucose damages glomerular capillaries through several overlapping mechanisms:

Advanced glycation end-products (AGEs): High glucose causes glucose molecules to attach non-enzymatically to proteins throughout the body — a process called glycation. In the glomerular basement membrane, this produces AGEs that cross-link and stiffen structural proteins, thickening the basement membrane and impairing its selective filtration properties.
Glomerular hypertension: High glucose causes the afferent arteriole (the vessel entering the glomerulus) to dilate while the efferent arteriole (the vessel exiting) constricts, increasing hydraulic pressure within the glomerular capillaries. This glomerular hypertension accelerates structural damage to capillary walls and is the primary reason why blood pressure control is so critical for kidney protection in diabetes.
Mesangial expansion: The mesangium — the connective tissue framework between glomerular capillaries — expands due to matrix protein accumulation driven by high glucose. This expansion progressively reduces the filtering surface area of the glomerulus.
Inflammation and oxidative stress: Elevated glucose activates inflammatory pathways (including NF-κB) and produces reactive oxygen species that damage glomerular endothelial cells, podocytes (the specialized cells that form the final filtration barrier), and the tubular cells that reabsorb filtered substances.

The cumulative result of these processes is a kidney that progressively loses its ability to filter blood efficiently — a decline measured by the glomerular filtration rate (GFR) — and that leaks protein (primarily albumin) into the urine. Our guide on what is insulin resistance covers how insulin resistance drives the metabolic environment in which these kidney-damaging processes occur.

The Scale of Diabetic Kidney Disease Approximately 1 in 3 adults with diabetes has some degree of chronic kidney disease. In the United States alone, diabetes-related kidney failure accounts for roughly 50,000 new cases of end-stage renal disease each year, making diabetes far and away the leading cause of kidney failure. People with both diabetes and chronic kidney disease face dramatically elevated risks of cardiovascular death — the leading cause of death in this population — as well as the progression to dialysis or transplantation that profoundly affects quality of life. Early identification and intervention can slow or halt this progression for many patients.

Stages of Kidney Disease in Diabetes

Diabetic nephropathy progresses through identifiable stages characterized by changes in urinary albumin and GFR. Recognizing these stages helps determine appropriate monitoring frequency and treatment intensity:

Stage 1 — Hyperfiltration (eGFR >90, no albuminuria): In early diabetes, the kidney actually filters at above-normal rates due to glomerular vasodilation driven by high glucose. No albumin is detectable in urine yet. This stage is reversible with blood glucose control.
Stage 2 — Microalbuminuria (eGFR >60, urine ACR 30–300 mg/g): Small but abnormal amounts of albumin begin leaking into the urine — the earliest detectable sign of glomerular damage. This stage, now called “moderately increased albuminuria” in current CKD classification, is still potentially reversible with aggressive blood glucose and blood pressure control. This is the critical intervention window.
Stage 3 — Macroalbuminuria (eGFR 30–59, urine ACR >300 mg/g): Larger albumin losses indicate significant glomerular damage. GFR has declined into the moderate range. Progression can be substantially slowed but is less often reversed at this stage.
Stage 4 — Severely reduced GFR (eGFR 15–29): The kidneys retain only a fraction of normal function. Preparation for renal replacement therapy (dialysis or transplantation) typically begins at this stage.
Stage 5 — Kidney failure / ESRD (eGFR <15): Renal replacement therapy — hemodialysis, peritoneal dialysis, or kidney transplantation — is required for survival.

A critical clinical insight is that people with diabetes can have significant kidney disease — even Stage 3 CKD with meaningfully reduced GFR — without any symptoms. Kidney disease does not cause pain. Symptoms such as leg swelling, fatigue, nausea, and decreased urine output typically only appear at Stage 4 or 5, by which point substantial irreversible damage has already occurred. This is why annual screening is non-negotiable for everyone with diabetes, regardless of how well they feel.

doctor reviewing kidney function test results eGFR and urine albumin with a patient with type 2 diabetes — Annual kidney function monitoring — including eGFR and urine albumin-to-creatinine ratio — is the cornerstone of early detection in diabetes, allowing protective treatment to begin before significant kidney damage has occurred.

How to Monitor Kidney Health With Diabetes

The ADA recommends that all people with Type 2 diabetes begin kidney function screening at diagnosis, and people with Type 1 diabetes begin screening after 5 years. Annual monitoring should include two tests:

Urine albumin-to-creatinine ratio (ACR): A first-morning urine sample is tested for the ratio of albumin to creatinine (to correct for urine concentration). Below 30 mg/g is normal; 30–300 mg/g indicates moderately increased albuminuria; above 300 mg/g indicates severely increased albuminuria. Because transient elevations can occur with exercise, illness, fever, or high-protein meals, an elevated result should be confirmed with a repeat test before clinical decisions are made.
Estimated glomerular filtration rate (eGFR): Calculated from a serum creatinine blood test along with age, sex, and race (though race-based equations are being phased out in favor of newer race-free equations). eGFR estimates how many milliliters of blood the kidneys filter per minute; normal is above 60 mL/min/1.73m², and decline below 60 for more than 3 months defines chronic kidney disease.

Together, ACR and eGFR define both the stage and prognosis of CKD in diabetes. A person with moderately reduced eGFR (45–59) and severely increased albuminuria (ACR >300) has a much higher risk of progression and cardiovascular events than someone with the same eGFR but normal albuminuria — the combination of both markers provides far more prognostic information than either alone. Our guide on diabetes and high blood pressure covers the blood pressure monitoring that complements kidney function testing in comprehensive diabetes management.

Blood Glucose and Blood Pressure Targets for Kidney Protection

The two most powerful modifiable factors for preventing or slowing diabetic nephropathy are blood glucose control and blood pressure control. Both must be managed simultaneously for optimal kidney protection:

Blood Glucose Targets

The landmark DCCT trial (Type 1 diabetes) and UKPDS trial (Type 2 diabetes) both demonstrated that intensive blood glucose control — targeting HbA1c below 7% — dramatically reduced the risk of developing microalbuminuria and slowed progression of established nephropathy. For most people with diabetes and early-stage kidney disease, an HbA1c target of 7.0–7.5% is appropriate. However, HbA1c targets must be individualized in advanced CKD: at eGFR below 30, red blood cell turnover changes in ways that make HbA1c unreliable, and hypoglycemia risk increases because many glucose-lowering medications are renally cleared and require dose adjustment or discontinuation. Our guides on Type 2 diabetes: causes and diagnosis and diabetes and heart disease cover the overlapping cardiovascular and metabolic goals that HbA1c targets serve.

Blood Pressure Targets

Current guidelines recommend a blood pressure target of below 130/80 mmHg for people with diabetes and CKD. The mechanism of kidney protection from blood pressure control is largely through reducing glomerular hypertension — high systemic blood pressure is transmitted directly into glomerular capillaries, accelerating their structural damage. Reducing blood pressure with medications that specifically target the renin-angiotensin-aldosterone system (RAAS) — ACE inhibitors and ARBs — provides kidney protection beyond what blood pressure reduction alone would predict, through direct reduction of intraglomerular pressure and anti-fibrotic effects in renal tubules. For this reason, ACE inhibitors or ARBs are the preferred first-line antihypertensive agents for people with diabetes and either hypertension or albuminuria, regardless of baseline blood pressure level.

Medications That Protect the Kidneys in Diabetes

Beyond blood glucose and blood pressure control, several medication classes have demonstrated specific kidney-protective effects in clinical trials:

ACE inhibitors and ARBs: These RAAS-blocking medications (examples: lisinopril, ramipril for ACE inhibitors; losartan, irbesartan for ARBs) reduce glomerular pressure, decrease proteinuria, and slow GFR decline in people with diabetic nephropathy. They are standard of care for all people with diabetes who have microalbuminuria or macroalbuminuria, regardless of blood pressure level. ACE inhibitors and ARBs should not be combined (dual RAAS blockade increases risk of acute kidney injury and hyperkalemia without additional benefit).
SGLT-2 inhibitors: Originally developed as glucose-lowering medications, SGLT-2 inhibitors (empagliflozin, dapagliflozin, canagliflozin) have demonstrated remarkable kidney-protective effects in dedicated cardiorenal outcome trials. The CREDENCE trial (canagliflozin) and DAPA-CKD trial (dapagliflozin) showed that SGLT-2 inhibitors reduced the risk of kidney failure, kidney death, and cardiovascular events by approximately 30% in people with diabetes and CKD on top of RAAS blockade. Their kidney-protective mechanism involves reducing glomerular hyperfiltration, lowering intraglomerular pressure, and decreasing kidney oxygen consumption — independently of their blood glucose effect. They are now recommended by major guidelines as a preferred add-on to ACE inhibitors or ARBs in people with diabetes, CKD, and eGFR above 20–25 mL/min.
Finerenone: A newer non-steroidal mineralocorticoid receptor antagonist (MRA), finerenone (Kerendia) was shown in the FIDELIO-DKD and FIGARO-DKD trials to reduce CKD progression and cardiovascular events in people with Type 2 diabetes and CKD when added to RAAS blockade. It addresses a mechanism not fully covered by ACE inhibitors, ARBs, or SGLT-2 inhibitors — aldosterone-driven inflammation and fibrosis in kidney tissue.
GLP-1 receptor agonists: Beyond their glucose-lowering and cardiovascular benefits, GLP-1 receptor agonists (semaglutide, liraglutide, dulaglutide) have shown reductions in albuminuria and slower CKD progression in trials. They are particularly valuable for people with diabetes, obesity, and CKD who need glucose lowering and kidney protection simultaneously.

Diet and Lifestyle for Kidney Health in Diabetes

Specific dietary modifications become increasingly important as kidney disease progresses:

Protein intake: Very high protein diets increase glomerular filtration demands and accelerate GFR decline in people with CKD. Current guidelines recommend 0.8 g of protein per kilogram of body weight per day for people with diabetes and CKD — similar to the general population recommendation — avoiding both very low and very high protein intakes.
Sodium restriction: Low-sodium diets (below 2,300 mg sodium per day) enhance the kidney-protective effects of ACE inhibitors and ARBs by reducing renin-angiotensin system activation driven by volume depletion. Sodium restriction also helps blood pressure control, which as described above is critical for kidney protection.
Potassium management: As eGFR declines below 30–45 mL/min, the kidneys lose the ability to excrete potassium efficiently, causing hyperkalemia (elevated blood potassium) — a potentially dangerous electrolyte imbalance that can cause cardiac arrhythmias. People with advanced CKD may need to limit high-potassium foods (bananas, potatoes, oranges, tomatoes, beans). This should be guided by a renal dietitian rather than self-directed restriction.
Phosphorus management: Similarly, advanced CKD impairs phosphorus excretion, leading to elevated phosphorus levels that cause bone disease, vascular calcification, and cardiovascular risk. Limiting processed foods (which contain large amounts of phosphate additives) is the most practical phosphorus management strategy for most people with early-to-moderate CKD.

Working with a renal dietitian — a registered dietitian with specialized training in kidney disease — is strongly recommended for anyone with diabetes and Stage 3 or higher CKD. The dietary requirements of CKD (sometimes limiting potassium, phosphorus, protein, and sodium simultaneously) can conflict with the dietary advice typically given for diabetes management alone, requiring individualized guidance.

Warning Signs That Kidney Function May Be Declining

Because kidney disease progresses silently in its early and middle stages, most people with diabetic nephropathy have no symptoms until function is already severely reduced. However, certain signs — when they do appear — warrant immediate evaluation:

Swelling in the ankles, feet, or legs (edema): When the kidneys lose the ability to excrete sodium and water efficiently, fluid accumulates in the body’s tissues, particularly the lower extremities. Significant edema in people with diabetes warrants kidney function testing. Edema can also be caused by heart disease (common in people with diabetes) or venous insufficiency, so evaluation is needed to identify the cause.
Foamy or frothy urine: Large amounts of protein in the urine — macroalbuminuria or nephrotic-range proteinuria — create foam in the toilet bowl that persists after flushing. While some foaminess can be normal (particularly with forceful urination), persistent foam that resembles detergent bubbles is a sign worth investigating.
Fatigue and difficulty concentrating: As kidney function declines, waste products (uremic toxins) that the kidneys normally clear begin to accumulate in the bloodstream. This uremic state produces fatigue, difficulty concentrating, loss of appetite, and a general sense of feeling unwell that many people mistakenly attribute to aging, diabetes itself, or depression.
Decreased urine output or changes in urination: In advanced CKD, the kidneys lose the ability to produce adequate urine volume. Conversely, in early CKD some people urinate more frequently at night (nocturia) because the kidneys cannot concentrate urine effectively.
Itching (pruritus): Accumulation of uremic toxins and phosphorus in the skin causes persistent itching that does not respond to topical treatments — a symptom characteristic of advanced kidney disease.
Nausea, poor appetite, and metallic taste: Elevated uremic toxins affect the gastrointestinal tract, causing nausea and appetite suppression. A metallic or ammonia-like taste in the mouth is a recognized symptom of significant uremia.

Importantly, these symptoms appear only at Stage 4 or 5 CKD — meaning that by the time symptoms emerge, kidney disease has already been present for many years and significant irreversible damage has occurred. This underscores why annual ACR and eGFR testing is critical even in people who feel perfectly well.

How Diabetes Medications Are Affected by Kidney Disease

An important but often overlooked aspect of diabetes and kidney health is that declining kidney function changes how many diabetes medications are handled by the body — requiring dose adjustments, substitutions, or discontinuation to avoid dangerous side effects:

Metformin: The most commonly used diabetes medication, metformin is renally cleared and, at low eGFR, can accumulate to levels that increase risk of lactic acidosis (a rare but serious complication). Current guidelines recommend dose reduction when eGFR falls below 45 mL/min and discontinuation when eGFR falls below 30 mL/min. People with eGFR above 45 can generally continue metformin safely.
Sulfonylureas: Older sulfonylureas (glibenclamide, glipizide) have active renally-cleared metabolites that accumulate in CKD, dramatically increasing hypoglycemia risk. Glipizide is preferred over glyburide in CKD because its metabolites are less active. Dose reduction or avoidance is recommended when eGFR falls below 30 mL/min.
SGLT-2 inhibitors: These medications require adequate kidney function to work (they act by blocking renal glucose reabsorption). Their glucose-lowering effect diminishes as eGFR falls, and they are generally not effective for glucose lowering below eGFR 45 mL/min. However, their cardiovascular and kidney-protective effects persist at lower eGFR levels, and current guidelines recommend continuing them for organ protection down to eGFR 20 mL/min even after their glucose-lowering benefit is minimal.
GLP-1 receptor agonists: Most GLP-1 receptor agonists can be used safely across a wide range of kidney function, including in CKD Stage 3 and 4. Semaglutide and dulaglutide do not require dose adjustment for CKD. They are increasingly used in people with both diabetes and advanced CKD who need safe, effective glucose lowering.
Insulin: Insulin itself is partially degraded by the kidneys, meaning insulin requirements may decrease as CKD progresses — paradoxically, some people with advanced CKD need less insulin to achieve the same glycemic control than they did with better kidney function. This must be monitored carefully to avoid hypoglycemia.

Any person with diabetes whose kidney function changes significantly — whether newly diagnosed CKD or a meaningful decline in eGFR — should have their entire diabetes medication regimen reviewed by their healthcare provider. Medication adjustments that were appropriate at eGFR 60 may be dangerous at eGFR 30.

When to See a Nephrologist The ADA recommends referral to a nephrologist (kidney specialist) when eGFR falls below 30 mL/min, when there is uncertainty about the diagnosis of CKD in diabetes (some kidney diseases in people with diabetes are not diabetic nephropathy and require specific treatment), or when CKD is progressing rapidly despite optimal diabetes and blood pressure management. Earlier referral (eGFR below 45) is appropriate for people with rapidly declining GFR, difficult-to-control blood pressure, or complications of CKD such as anemia, metabolic bone disease, or electrolyte abnormalities. Nephrologists and endocrinologists working together — in a coordinated care model — provide the best outcomes for people with diabetes and advanced kidney disease.

Reducing Cardiovascular Risk When You Have Diabetes and CKD

People with both diabetes and CKD face a particularly high cardiovascular risk — they are substantially more likely to die from a cardiovascular event (heart attack, heart failure, stroke) than to progress to dialysis. This is because CKD itself is a major cardiovascular risk factor, independently of traditional risk factors like cholesterol and blood pressure. The combination of diabetes and CKD produces a cardiovascular risk profile that rivals established coronary artery disease. Managing this combined risk requires attention to several factors simultaneously:

Statin therapy: High-intensity statin therapy is recommended for most people with diabetes and CKD to reduce LDL and cardiovascular event risk. Our guide on diabetes and cholesterol covers the lipid management that is equally important alongside kidney protection.
Aspirin: Low-dose aspirin (81 mg/day) is recommended for people with diabetes and established cardiovascular disease or high cardiovascular risk, including those with CKD Stage 3 or higher. The risk of GI bleeding with aspirin must be balanced against cardiovascular benefit on an individual basis.
SGLT-2 inhibitors and GLP-1 agonists: As noted above, both medication classes reduce cardiovascular events in people with diabetes and cardiovascular disease or CKD — making them particularly valuable in the high-risk population of people with both diabetes and kidney disease.
Anemia management: CKD causes anemia (reduced red blood cell production due to decreased erythropoietin from damaged kidney tissue) that worsens cardiovascular outcomes. Anemia treatment with erythropoiesis-stimulating agents or oral iron is part of comprehensive CKD-cardiovascular management.

People with diabetes who have been told they have any degree of kidney disease — even early microalbuminuria — should ensure they are receiving the comprehensive cardiovascular risk reduction described above. The combination of kidney protection and cardiovascular risk reduction is the cornerstone of modern diabetic nephropathy management. Our guide on diabetes and heart disease provides the broader cardiovascular context for this integrated approach.

Sources: American Diabetes Association. “Chronic Kidney Disease and Risk Management.” Diabetes Care 2024. | NIDDK — Diabetic Kidney Disease. | National Kidney Foundation — Diabetes and Kidney Disease. | Mayo Clinic — Diabetic Nephropathy. | Perkovic V, et al. “Canagliflozin and Renal Outcomes in Type 2 Diabetes and Nephropathy.” NEJM 2019.