What is chronic kidney disease?

Chronic kidney disease — often called CKD — means your kidneys are not working as well as they should, and the damage has been happening gradually over time. Your kidneys are two fist-sized organs that sit in your lower back. Their main job is to filter your blood — removing waste, extra salt, and excess water, which leave your body as urine.

When the kidneys are damaged, they can't do this job properly. Waste starts to build up in your blood, and over time this can affect almost every part of your body. The word "chronic" simply means long-lasting — this is not a sudden illness but a condition that develops over months or years.

Important to know: CKD is very common. About 1 in 7 American adults has it — and many don't know because early CKD causes no symptoms. That's why regular blood and urine tests matter.

What causes CKD?

The two most common causes of CKD are diabetes and high blood pressure. Together they account for about two-thirds of all cases.

Diabetes — High blood sugar over many years damages the tiny blood vessels inside the kidneys, making them less able to filter properly.
High blood pressure (hypertension) — Persistently high pressure in your blood vessels damages the kidneys over time. And damaged kidneys can make blood pressure worse — it's a two-way relationship.
Glomerulonephritis — Inflammation of the kidneys' filtering units (glomeruli), often due to an immune system problem.
Polycystic kidney disease — A genetic condition where fluid-filled cysts grow in the kidneys over time.
Repeated kidney infections or urinary blockages — These can scar the kidneys if not treated properly.
Certain medications taken long-term — Especially NSAIDs like ibuprofen and naproxen (Advil, Aleve).

What are the symptoms?

This is one of the most important things to understand about CKD: in the early stages, there are usually no symptoms at all. The kidneys have a remarkable ability to compensate — they can be working at 50% of normal function and you may feel completely fine.

As CKD progresses, symptoms may begin to appear:

  • Fatigue and low energy — waste building up in your blood makes you feel tired
  • Swelling in your feet, ankles, or hands — kidneys aren't removing enough fluid
  • Changes in urination — going more or less often, foamy urine (protein), or blood in urine
  • Shortness of breath — fluid can build up around the lungs
  • Nausea, loss of appetite, or a metallic taste in your mouth
  • Difficulty concentrating or sleeping
  • Itching — waste products accumulating in the skin
  • Muscle cramps, especially at night
Don't wait for symptoms to get your kidney function checked. If you have diabetes or high blood pressure, ask your doctor for a kidney function test every year — even if you feel fine.

How is CKD diagnosed?

CKD is diagnosed with two simple tests that your doctor can order:

Blood test — eGFR (estimated glomerular filtration rate)

This measures how well your kidneys are filtering your blood. A normal eGFR is 90 or above. The lower your eGFR, the less well your kidneys are working. Your eGFR determines which stage of CKD you have (Stage 1 through 5).

Urine test — UACR (urine albumin-to-creatinine ratio)

This checks for protein (specifically albumin) leaking into your urine. Healthy kidneys keep protein in the blood. When kidneys are damaged, protein leaks through into the urine — this is an early warning sign of kidney disease, sometimes appearing before eGFR drops.

Your doctor may also order imaging (ultrasound or CT scan) to look at the size and shape of your kidneys, or in some cases a kidney biopsy to identify the specific cause of your CKD.

The 5 stages of CKD

CKD is classified into five stages based on your eGFR. Knowing your stage helps you and your care team make the right decisions.

Stage 1 (eGFR ≥ 90) — Kidney damage present but function is normal or near-normal. No symptoms. Focus on protecting kidney function.
Stage 2 (eGFR 60–89) — Mild loss of function. Still usually no symptoms. Lifestyle changes have the greatest impact here.
Stage 3 (eGFR 30–59) — Moderate loss. Symptoms may begin to appear. Active management is essential.
Stage 4 (eGFR 15–29) — Severe loss. Time to prepare for renal replacement therapy (dialysis or transplant).
Stage 5 / ESRD (eGFR <15) — Kidney failure. Dialysis or a kidney transplant is necessary to survive.

Can CKD be treated?

CKD cannot be reversed, but its progression can almost always be slowed — and in some cases nearly stopped — with the right treatment and lifestyle changes. This is why early diagnosis matters so much.

Controlling blood pressure

Keeping blood pressure below 130/80 is one of the most powerful ways to protect your kidneys. Certain blood pressure medications — ACE inhibitors and ARBs — also directly protect the kidneys beyond just lowering pressure. Your nephrologist will prescribe the right combination for you.

Managing blood sugar

If you have diabetes, tight blood sugar control significantly slows CKD progression. Newer medications like SGLT2 inhibitors (Jardiance, Farxiga) have been shown to directly protect the kidneys in addition to controlling blood sugar.

Diet changes

A kidney-friendly diet is an important part of managing CKD. This typically means reducing sodium, watching potassium and phosphorus intake (especially in later stages), limiting protein, and staying well hydrated. Your nephrologist can refer you to a renal dietitian for a personalized plan.

Avoiding medications that harm kidneys

NSAIDs like ibuprofen (Advil, Motrin) and naproxen (Aleve) can worsen kidney function. Talk to your doctor about safe alternatives for pain relief. Always tell any new doctor or pharmacist that you have CKD.

Good news: Many patients with CKD live full, active lives for decades. Working closely with a nephrologist and following your treatment plan makes a real difference.