Diabetes and Kidney Health: Signs, Tests, and How to Protect Your Kidneys
Your kidneys don't complain. They can lose a good deal of their filtering power before you feel a single symptom, and that's precisely what makes kidney damage such a quiet complication of diabetes. The good news is that it's also one of the most preventable and one of the easiest to catch early with a simple test.
This guide explains the link between diabetes and kidney health: how high blood sugar harms the kidneys, what to watch for, which tests matter, and the practical steps that protect them. It's part of our complete guide to type 2 diabetes, and it's general education, not medical advice.
What Do the Kidneys Do?
You have two kidneys, each about the size of a fist, and each packed with around a million tiny filtering units. They remove waste and extra fluid from your blood, balance salt and minerals, help control blood pressure, and support red blood cell production and bone health. When they work well, you barely think about them.
Diabetes puts this system under strain. According to the NIDDK, diabetes is a leading cause of chronic kidney disease, and roughly one in three adults with diabetes has some degree of kidney disease.
How Diabetes Damages the Kidneys
Persistently high blood sugar damages small blood vessels throughout the body, including the delicate filters in the kidneys. Over time, those filters become leaky, letting protein, mainly albumin, escape into the urine. The Mayo Clinic describes this condition as diabetic nephropathy.
High blood pressure makes things worse. It adds pressure on the same fragile filters, and kidney damage, in turn, can raise blood pressure further, creating a harmful loop. That's why controlling both blood sugar and blood pressure matters so much.
Related reading: What Causes High Blood Sugar?
Signs and Symptoms of Diabetic Kidney Disease
In the early stages, there are usually no symptoms at all. As kidney function declines, some people notice:
- Foamy or bubbly urine
- Swelling in the feet, ankles, hands, or around the eyes
- Fatigue and weakness
- Nausea, poor appetite, or a metallic taste in the mouth
- Itchy skin
- Changes in how often you urinate
- Rising blood pressure that is hard to control
These usually show up late. The NHS notes that many people with kidney disease have no symptoms until it's advanced, which is why testing rather than waiting for symptoms is the safer path.
The Tests That Catch Kidney Problems Early
Two simple tests do most of the work, as outlined by the NIDDK guide to kidney disease tests:
- Urine albumin-to-creatinine ratio (uACR). A urine sample that checks for albumin leaking through the filters. It's often the earliest sign of trouble.
- Estimated glomerular filtration rate (eGFR). A blood test for creatinine is converted into a score that estimates how well your kidneys filter.
The American Diabetes Association Standards of Care recommend checking both at least once a year for most people with type 2 diabetes, starting at diagnosis. An abnormal result is usually repeated after a few weeks or months to confirm it, because levels can vary.
Understanding Your eGFR
| Stage GFR | R (mL/min/1.73 m²): | What it generally means |
|---|---|---|
| 1 | 90 or higher | Normal filtration, but other signs of kidney damage may be present |
| 2 | 60 to 89 | Mildly reduced filtration |
| 3a | 45 to 59 | Mild to moderate reduction |
| 3b | 30 to 44 | Moderate to severe reduction |
| 4 | 15 to 29 | Severe reduction |
| 5 | Below 15 | Kidney failure |
Stages are based on eGFR and on how much albumin is in the urine. Your provider interprets both together, and a single result isn't a diagnosis.
How Often Should You Be Checked?
| Check | Typical frequency | Why it matters |
|---|---|---|
| Urine albumin (uACR) and eGFR | At least once a year | Detects kidney changes before symptoms |
| Blood pressure | At every visit, plus home checks if advised | High pressure speeds up kidney damage |
| HbA1c | Two to four times a year | Shows long-term blood sugar control |
| Cholesterol | About once a year | Protects the heart and blood vessels |
| Dilated eye exam | Usually, once a year | Eye and kidney damage often go together |
Your HbA1c tells you how well your blood sugar has been controlled over about three months. It is one of the strongest levers you have over kidney risk.
10 Ways to Protect Your Kidneys
1. Keep Blood Sugar in Your Target Range
Steady blood sugar reduces strain on the kidneys' small vessels. Agree on your targets with your care team, and see How to Lower Blood Sugar Safely for practical steps.
2. Control Your Blood Pressure
For many adults with diabetes, guidelines suggest keeping blood pressure below 130/80, though your own goal may differ. Lifestyle changes help, and many people also need medication.
3. Ask About Kidney-Protective Medicines
Some medicines do more than lower blood sugar or pressure. ACE inhibitors and ARBs are often used to protect the kidneys in people with albumin in their urine, and certain diabetes drugs (SGLT2 inhibitors, for example) have shown kidney benefits. Whether they are right for you is a decision for your provider.
4. Go Easy on Salt
Too much sodium raises blood pressure and increases albumin leakage. Cook with herbs, spices, lemon, and garlic in place of extra salt, and be aware of hidden sodium in processed foods, stock cubes, and takeaways.
5. Get Your Protein Right
More is not better. Very high-protein diets can add work for the kidneys, and people with established kidney disease are often advised to adjust their intake. A registered dietitian can set a target based on your test results.
6. Eat a Balanced, Mostly Whole-Food Diet
Vegetables, legumes, whole grains, and healthy fats support blood sugar, weight, and blood pressure together. Our best foods guide and meal planning guide are good places to start. If your kidney function is reduced, you may need to limit certain foods, so confirm changes with a dietitian.
7. Stay Active
Regular activity helps with blood sugar, blood pressure, and weight, all of which affect the kidneys. See Exercise and Blood Sugar for how to get started safely.
8. Don't Smoke
Smoking damages blood vessels and speeds up kidney decline in people with diabetes. Quitting is one of the most powerful things you can do for your kidneys, your heart, and your eyes.
9. Be Careful with Painkillers and Supplements
Regular use of NSAID painkillers, such as ibuprofen and naproxen, can harm the kidneys, particularly if function is already reduced. Some herbal products and supplements can also be risky. Check with your pharmacist or provider before using them, and never assume something is safe because it's natural.
10. Keep Your Appointments
Screening only works if it happens. Put your yearly kidney tests in the calendar, and bring a list of all your medicines to appointments. Some diabetes medicines need dose changes as kidney function changes, so never adjust them yourself.
Stay Hydrated, and Have a Sick-Day Plan
Dehydration is hard on the kidneys. Drink water regularly, especially in hot weather. When you're ill with vomiting, diarrhea, or fever, your kidneys are at greater risk, and some medicines may need to be paused temporarily. Ask your provider in advance for a sick-day plan, so you know what to do rather than guess when you're unwell.
Myths About Diabetes and the Kidneys
- "If my kidneys were damaged, I'd feel it." Not usually. Early kidney disease is silent, which is why testing matters.
- "Kidney damage from diabetes is inevitable." No. Many people never develop it, and good control lowers the risk significantly.
- "Once it starts, nothing helps." Early treatment can slow progression a great deal.
- "Drinking lots of water will flush out kidney disease." Staying hydrated is good, but water alone won't prevent or reverse kidney damage.
When to Seek Medical Help
Contact your healthcare team if you notice swelling in your legs or around your eyes, foamy urine, a marked change in how much you urinate, or new tiredness and nausea. Seek urgent care for confusion, severe shortness of breath, chest pain, very little or no urine, or extreme drowsiness. Very high blood sugar can also become an emergency, as the Mayo Clinic explains.
Related reading: Diabetes and Eye Health · Diabetes and Foot Care
Frequently Asked Questions
Can diabetes cause kidney failure?
It can, and diabetes is a leading cause of chronic kidney disease. But many people never reach that point, and early detection and treatment slow progression a great deal.
What is the earliest sign of diabetic kidney disease?
A small amount of albumin in the urine, found on a uACR test, is usually the earliest sign. It typically has no symptoms.
How often should I get my kidneys tested if I have diabetes?
At least once a year for most people, with a urine albumin test and an eGFR blood test. Your provider may check more often if results are abnormal.
Can kidney damage from diabetes be reversed?
Early changes can sometimes improve with good control of blood sugar and blood pressure and with the right medicines. More advanced damage usually can't be reversed, but it can often be slowed.
Do I need to avoid protein if I have diabetes?
Not necessarily. But very high intake isn't recommended, and people with kidney disease may need a tailored amount. A dietitian can guide you.
Which painkillers are safer for the kidneys?
It depends on your health and other medicines. NSAIDs like ibuprofen can harm the kidneys in some people, so check with your pharmacist or provider before using them.
Key Takeaways
- Diabetes is a leading cause of chronic kidney disease, but kidney damage is not inevitable.
- Early kidney disease usually has no symptoms, so yearly uACR and eGFR tests are essential.
- Blood sugar control, blood pressure control, and not smoking are the pillars of kidney protection.
- Certain medicines protect the kidneys, and your provider can advise which suit you.
- Be careful with NSAID painkillers and supplements, and follow a sick-day plan.
- Never change diabetes or blood pressure medicines on your own.
References
- National Institute of Diabetes and Digestive and Kidney Diseases. Diabetic Kidney Disease. https://www.niddk.nih.gov/health-information/diabetes/overview/preventing-problems/diabetic-kidney-disease Supports how common kidney disease is in diabetes and how it develops.
- National Institute of Diabetes and Digestive and Kidney Diseases. Tests and Diagnosis for Chronic Kidney Disease. https://www.niddk.nih.gov/health-information/kidney-disease/chronic-kidney-disease-ckd/tests-diagnosis Supports the uACR and eGFR tests.
- American Diabetes Association. Standards of Care in Diabetes. https://professional.diabetes.org/standards-of-care Supports yearly screening recommendations and blood pressure goals.
- Mayo Clinic. Diabetic Nephropathy: Symptoms and Causes. https://www.mayoclinic.org/diseases-conditions/diabetic-nephropathy/symptoms-causes/syc-20354556 Supports how diabetes damages the kidneys and its symptoms.
- Mayo Clinic. Chronic Kidney Disease: Symptoms and Causes. https://www.mayoclinic.org/diseases-conditions/chronic-kidney-disease/symptoms-causes/syc-20354521 Supports general CKD information.
- National Health Service (UK). Kidney Disease. https://www.nhs.uk/conditions/kidney-disease/ Supports the point that early kidney disease often has no symptoms.
- Mayo Clinic. Hyperglycemia in Diabetes: Symptoms and Causes. https://www.mayoclinic.org/diseases-conditions/hyperglycemia/symptoms-causes/syc-20373631 Supports emergency warning signs of very high blood sugar.
General background on kidney-protective medicines, sodium, protein intake, NSAIDs, and sick-day guidance reflects consistent guidance from the American Diabetes Association, CDC, and NIDDK patient-education materials, paraphrased rather than drawn from a single source per claim.
