Diabetes and CKD: what it means and how to protect your kidneys

Diabetes, type 1 or type 2, keeps sugar (glucose) in the blood above the healthy range. Over the years, that sugar damages small blood vessels all over the body, including the kidneys' built-in filters, tiny clusters of blood vessels called glomeruli. Damaged glomeruli first let albumin, a useful protein, slip into the urine. Over time they scar and lose the ability to remove waste and extra fluid from the blood.Kidney disease caused by diabetes is called diabetic kidney disease or diabetic nephropathy. About one in three adults with diabetes also has CKD, and diabetes remains the most common reason people start dialysis. The damage builds slowly and silently, which is why testing matters more than waiting for symptoms.

Things that speed up kidney damage in diabetes

• Blood sugar that stays high over many years

• High blood pressure, the second leading cause of CKD

• Smoking, which narrows the small vessels the kidneys depend on

• Long duration of diabetes, especially beyond 10 to 15 years

The good news: each of these risks can be treated or reduced, and the steps that protect your kidneys protect your heart and eyes too.

Because early diabetic kidney disease causes no symptoms, it is found with two simple tests that are usually done at least once a year. The results also show the stage of CKD, from stage 1 through stage 5.

• eGFR (estimated glomerular filtration rate): a blood test that estimates how well your kidneys clean the blood. Above 60 for three months or more is usually normal or mildly reduced; below 60 suggests CKD.

• uACR (urine albumin-to-creatinine ratio): a urine test that detects albumin leakage. Below 30 mg/g is normal; 30 to 300 mg/g signals moderately increased damage; above 300 mg/g signals severe damage.

A diagnosis of CKD needs abnormal results that persist for at least three months, so your clinician will usually repeat the tests before labelling it. One odd result, for example after hard exercise or dehydration, does not confirm kidney disease.

When testing starts

• Type 2 diabetes: kidney testing starts at diagnosis, because damage may already be present, then at least once a year.

• Type 1 diabetes: kidney testing usually starts about five years after diagnosis, then at least once a year.

• If results are abnormal or eGFR is below 60, testing becomes more frequent.

Later on, warning signs can appear: foamy or bubbly urine, swelling of the ankles, feet, or around the eyes, unusual tiredness, or getting up at night to urinate more often. These deserve a prompt visit rather than waiting for the yearly check.

Most of the work of protecting your kidneys happens at home, not in the clinic. The same habits that protect your heart also protect the kidneys' small vessels.

Keep blood sugar in your target range

Your clinician sets a personal target based on your age and health, often an A1C below 7% for many adults. Kidney disease can change how diabetes medicines work and raise the risk of low blood sugar, so your targets and doses may be adjusted as kidney function changes. Ask before you change anything yourself.

Keep blood pressure under control

High blood pressure both causes and accelerates kidney damage. Many people with diabetes and CKD aim for a reading at or below 130/80 mm Hg, but follow the target your own clinician sets. Home blood pressure checks, cutting back on salt, and prescribed blood pressure tablets all help.

Take kidney-protective medicines if they are prescribed

ACE inhibitors (names ending in -pril) and ARBs (names ending in -sartan) lower blood pressure and reduce albumin leakage, which protects the kidneys over years. SGLT2 inhibitors, a class of diabetes tablets such as empagliflozin and dapagliflozin, slow CKD progression and also protect the heart. Cholesterol tablets (statins) reduce the risk of heart disease, the main cause of death in people with CKD. Take these medicines as prescribed, and do not stop them because you feel fine, since kidney damage is silent.

Everyday habits that help

• Do not smoke, and ask for help quitting if you need it

• Move most days: walking, cycling, or swimming for about 30 minutes

• Keep to the eating plan you and your dietitian agree on

• Limit alcohol, and aim for a healthy weight

Some common medicines can strain kidneys that are already working harder. Before you buy anything over the counter, check with your clinician or pharmacist and mention that you have diabetes or CKD.

• NSAIDs such as ibuprofen, naproxen, and high-dose aspirin: regular use can reduce kidney blood flow. Acetaminophen (paracetamol) is often a safer choice for occasional pain.

• Herbal supplements and so-called kidney cleanses: some are directly harmful to kidneys, and few have been tested in people with CKD.

• Contrast dyes used in some scans: tell the imaging team you have diabetes or CKD so they can choose the safest approach.

• Salt substitutes: many contain potassium chloride, which is not safe for everyone with reduced kidney function. Ask first.

Vomiting, diarrhoea, or an illness that stops you drinking can quickly dehydrate you and put strain on the kidneys. Some medicines, including metformin, ACE inhibitors, ARBs, SGLT2 inhibitors, and diuretics, are sometimes paused temporarily during such sick days, but only on your clinician's advice. Call your team if the illness lasts more than a day, rather than deciding on your own.

Diabetic kidney disease usually moves slowly, but a few situations need immediate attention. Knowing the difference between an emergency, a same-day problem, and something that can wait for a routine visit keeps you safe without panic.

Call your care team the same day if you have:

• Vomiting or diarrhoea lasting more than a day, or illness that stops you drinking

• Fever together with much less urine than usual

• Sudden weight gain over a few days or new swelling in your legs or around your eyes

• Blood sugar readings repeatedly above or below the range you agreed with your team

• Blood in the urine

Safe to arrange at your next routine visit:

• Foamy urine or mild ankle swelling without any of the warning signs above

• Lab results showing a slowly falling eGFR or slowly rising uACR

• Planning for scans or new medicines while you have CKD

• Yearly kidney tests, eye checks, and vaccinations

Once CKD is found, your team will usually repeat eGFR and uACR at least once a year, and more often from stage 3 onward, alongside your A1C every three to six months and blood pressure checks at each visit. Eye and foot exams matter too, and vaccines such as influenza, pneumococcal, and hepatitis B are recommended for many people with diabetes or CKD. A kidney dietitian can tailor an eating plan that fits both conditions.

This may sound like a lot, but the outlook is genuinely encouraging. Many people with diabetic kidney disease keep stable kidney function for decades, especially when the problem is found early and blood sugar and blood pressure stay controlled.

Questions to bring to your next appointment

• What are my latest eGFR and uACR results, and what stage am I at?

• How often should my kidneys be checked?

• Which of my medicines protect my kidneys, and which should I avoid?

• What blood sugar and blood pressure targets are right for me?

• Should I see a kidney dietitian?

For more on the tests themselves, see our guides to eGFR and the urine albumin test, and on keeping blood pressure in check, see blood pressure and kidney health.