Diabetes and Kidney Health: What It Means and What to Ask

Diabetic kidney disease is kidney damage caused by diabetes. It is also called diabetic nephropathy, kidney disease of diabetes, or CKD caused by diabetes. In the United States, diabetes is a leading cause of kidney failure, and current CDC estimates suggest that about 4 in 10 adults with diabetes have CKD.

Diabetes damages the kidneys through the small blood vessels inside them. When blood glucose stays high for years, those vessels become stiff and leaky. Many people with diabetes also have high blood pressure, which adds a second strain on the same vessels. Both problems tend to work silently: most people with early diabetic kidney disease feel nothing.

The good news is that kidney damage from diabetes usually develops slowly and can be slowed or prevented. The tests are simple, the tools are proven, and the steps that protect the kidneys overlap heavily with the steps that protect the heart.

The kidneys are two small organs that filter waste and extra fluid out of the blood to make urine. Inside each kidney, millions of tiny blood vessels called glomeruli do the filtering. The process is simple to describe: when blood glucose is high for a long time, it damages these blood vessels, and the kidneys start to let albumin (a protein that should mostly stay in the blood) leak into the urine.

Two things drive most of the damage:

• High blood glucose. Sustained high glucose damages the filter vessels directly and stresses the cells that line them.

• High blood pressure. Many people with diabetes also develop high blood pressure, which constricts and narrows the kidney vessels, reducing blood flow and adding damage.

Sometimes the same processes also create inflammation and scarring (fibrosis) inside the kidney tissue. The result over years is a filter that leaks too much albumin and clears waste too slowly. This is why kidney tests use urine albumin and a blood estimate of filtration (eGFR).

Most people with diabetic kidney disease have no symptoms, so testing — not how you feel — is the only reliable way to find it. The NIDDK recommends annual kidney testing for everyone with type 2 diabetes, and for people with type 1 diabetes once the condition has lasted about five years.

Two simple tests are used together, and neither is exotic:

• A urine test for albumin, often reported as a urine albumin-to-creatinine ratio (uACR). This measures how much albumin leaks into urine.

• A blood test for estimated GFR (eGFR), which estimates how well the kidneys filter blood.

A high uACR is often the first sign that the kidneys are under strain, sometimes before eGFR falls. It is measured in mg per gram of creatinine (mg/g) or in mg/mmol. Kidney damage is present when uACR stays at or above 30 mg/g (3 mg/mmol), or when eGFR stays below 60 mL/min/1.73 m², for at least three months. The word “stays” matters: one unusual reading is not a diagnosis.

Slowing diabetic kidney disease is not one magic pill. It is a package, and your care team will tailor it. The four parts that matter most are glucose control, blood pressure control, the right medicines, and habits that reduce strain on the vessels.

Blood glucose: the A1C goal

The A1C test shows average glucose over about three months. For many people with diabetes the goal is below 7%, but the right target depends on your age, other conditions, and how often you have low glucose. Ask what your personal A1C target is — then treat it as a plan, not a grade.

Blood pressure: the numbers that matter

For most people with diabetes the blood pressure goal is below 140/90 mm Hg, and some guidelines suggest aiming lower. The same high blood pressure that damages the kidneys is also the number you and your care team can move the fastest.

Medicines: ACE inhibitors, ARBs, and SGLT2 inhibitors

Two classes of blood pressure medicines — ACE inhibitors (names ending in -pril) and ARBs (names ending in -sartan) — protect the kidneys beyond simply lowering pressure, especially in people with diabetes, high blood pressure, and albuminuria. They are among the reasons kidney damage can slow down.

SGLT2 inhibitors used to be thought of as diabetes medicines. Modern evidence shows that in people with CKD — with or without diabetes — they can slow kidney function decline and reduce heart risk. KDIGO 2024 recommends them for many people with CKD and type 2 diabetes, and increasingly for CKD without diabetes.

None of this is a do-it-yourself decision. Whether a medicine is right for you depends on your kidney function, potassium, hydration, and other medicines. Never stop or change a prescribed medicine on your own.

Habits that carry weight

• Stop smoking. Smoking damages blood vessels and speeds kidney decline.

• Keep sodium in check; processed and restaurant food tends to be high in salt.

• Move most days; even walking helps blood pressure and blood glucose.

• Reach and hold a healthier weight, and get 7 to 8 hours of sleep.

Blood results do not exist in a vacuum. Several things can change what a reading means, and knowing them helps you ask better questions.

• Dehydration from illness, heat, or too little fluid can raise creatinine and lower eGFR temporarily.

• A recent large meat meal can briefly raise creatinine.

• NSAIDs — ibuprofen and naproxen — can strain the kidneys; with diabetes and CKD, check with your care team before using them regularly.

• Acute events: a urinary infection or a short illness can push numbers up even when long-term kidney function is stable.

• Albumin levels fluctuate; that is why diagnosis needs repeated tests months apart.

A single abnormal result is a prompt to repeat the test, not proof of permanent damage. Sharp worsening over days, however, is different — see the emergency section below.

Most of living with diabetes and kidney disease is routine. Some situations are not routine.

Get urgent help right away

• Chest pain, shortness of breath, or fainting.

• Severe weakness that comes on quickly, or a new fast or irregular heartbeat.

• Urine output drops sharply or stops.

• Swelling suddenly becomes severe, or breathing feels harder lying down.

Call your care team within a day or two

• A new result that is much worse than your last one, especially if you were not expecting it.

• Blood glucose or blood pressure that stays far outside your targets for several days.

• A fever, or signs of a urinary infection (burning, urgency, cloudy or bloody urine).

• Possible medicine side effects: swelling, dizziness, or a rash after starting a new medicine.

Questions worth asking at your next appointment

• What is my current eGFR and uACR, and what will we compare them to next time?

• What is my personal A1C target and blood pressure target?

• Would an ACE inhibitor, ARB, or SGLT2 inhibitor help me, and are any of them right for my situation?

• Which medicines should I avoid or check with you before taking, such as ibuprofen or naproxen?

• Do I need a renal dietitian referral?