What is Stage 3 Kidney Disease and How It Develops
Stage 3 kidney disease means your kidneys are not working as well as they should, but you still have some kidney function remaining. Your kidneys filter waste and extra water from your blood to make urine. When kidneys become damaged, they cannot filter waste effectively, and harmful substances build up in your body.
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Stage 3 is actually divided into two parts: Stage 3a and Stage 3b. This division is based on something called the glomerular filtration rate, or GFR. Your GFR is a number that shows how much blood your kidneys filter each minute. In Stage 3a, your GFR is between 45 and 59. In Stage 3b, your GFR is between 30 and 44. A normal GFR is 90 or higher.
Many people develop Stage 3 kidney disease slowly over years or even decades. Common causes include high blood pressure, diabetes, and chronic glomerulonephritis (long-term inflammation of the kidney's filtering units). High blood pressure accounts for about 30% of kidney disease cases in the United States, while diabetes accounts for about 35%. Other causes include autoimmune diseases, kidney infections, and certain medications.
Stage 3 kidney disease often has no symptoms at first. You might feel completely normal even though your kidneys are not filtering as well as they should. This is why many people discover they have Stage 3 kidney disease during routine blood tests or checkups. Some people may eventually notice fatigue, swelling in the legs or feet, or changes in how often they urinate, but these symptoms can take years to appear.
Practical takeaway: If you have been diagnosed with Stage 3 kidney disease, understanding that you still have significant kidney function is important. This stage is often when treatment and lifestyle changes can slow down the disease's progression and help you stay healthier longer.
How to Monitor Your Kidney Health With Regular Testing
Regular testing is one of the most important parts of managing Stage 3 kidney disease. Your doctor will order blood tests and urine tests to check how your kidneys are working and to catch any changes early. These tests help track whether your kidney disease is staying the same, getting better, or getting worse.
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The most common blood test is called a serum creatinine test. Creatinine is a waste product that your kidneys filter out. When kidney function declines, creatinine builds up in your blood. Your doctor uses your creatinine level along with your age, gender, and race to calculate your GFR. The GFR number tells you and your doctor how much kidney function you have left. In Stage 3, you typically have 30 to 59% of normal kidney function.
Another important blood test measures your blood urea nitrogen, or BUN. Like creatinine, BUN is a waste product that builds up when kidneys don't filter well. Your doctor watches both numbers together to get a complete picture of kidney function. You should have these blood tests done at least once or twice per year if you have Stage 3 kidney disease, though your doctor may recommend more frequent testing if your numbers are changing.
Urine tests are also important. Your doctor may test your urine for protein, which can indicate kidney damage. A test called urine albumin-to-creatinine ratio (UACR) measures how much protein is in your urine. Healthy kidneys should not leak protein into urine. If protein appears in your urine, it suggests your kidney disease may need more careful management or different treatment approaches.
Your doctor may also check your blood pressure at every visit, since controlling blood pressure is crucial for slowing kidney disease. Additionally, blood tests for potassium, phosphorus, calcium, and other minerals become more important as kidney function declines, since damaged kidneys have trouble regulating these substances. You should keep a record of your test results over time so you can see trends and discuss them with your healthcare provider during visits.
Practical takeaway: Ask your doctor how often you should have blood and urine tests, what the results mean, and what changes in your numbers might indicate. Keeping track of your test results helps you understand your kidney disease and work with your doctor on a management plan.
Managing Blood Pressure and Blood Sugar to Slow Disease Progression
High blood pressure and high blood sugar are the two leading causes of kidney disease, and controlling both is critical for slowing Stage 3 kidney disease. If you have high blood pressure, your heart pumps harder, putting extra stress on blood vessels throughout your body, including in your kidneys. Over time, this damage makes it harder for your kidneys to filter blood. Similarly, high blood sugar from diabetes damages the tiny blood vessels in your kidneys.
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Blood pressure control is particularly important for people with kidney disease. The American Kidney Fund recommends a target blood pressure of less than 130/80 millimeters of mercury (mmHg) for most people with kidney disease, which is lower than the general population target. Your doctor may prescribe medications called ACE inhibitors or ARBs (angiotensin II receptor blockers) specifically because they help protect kidney function while also lowering blood pressure. Common ACE inhibitors include lisinopril and enalapril. Common ARBs include losartan and valsartan. These medications can slow the decline in kidney function by 20 to 30% in some people.
For people with diabetes and Stage 3 kidney disease, keeping blood sugar in a target range helps prevent additional kidney damage. This typically means keeping your hemoglobin A1C below 7%, though your target may be different depending on your age and health situation. You can manage blood sugar through a combination of medication, diet, and physical activity. Work with your doctor or a diabetes educator to understand your target numbers and how to monitor your blood sugar at home if needed.
Lifestyle changes support medication efforts significantly. Reducing sodium intake to less than 2,300 milligrams per day (about one teaspoon) helps lower blood pressure. Limiting alcohol use, managing stress through activities like walking or meditation, and getting enough sleep all support better blood pressure control. For people with diabetes, monitoring carbohydrate intake and eating regular, balanced meals helps keep blood sugar stable. Weight loss of even 5 to 10% of your body weight, if you are overweight, can lower blood pressure and improve blood sugar control.
Practical takeaway: Work with your healthcare team to set specific blood pressure and blood sugar targets for yourself. Ask which medications you are taking, why they were chosen, and what side effects to watch for. Regular monitoring of both blood pressure at home and blood sugar levels, if appropriate, helps you see whether your management plan is working.
Understanding Dietary Changes for Stage 3 Kidney Disease
Your diet plays a major role in managing Stage 3 kidney disease. As kidney function declines, your kidneys have more trouble regulating certain minerals and nutrients in your blood. Adjusting what you eat can reduce stress on your kidneys and help you feel better. However, dietary needs for kidney disease can be complex, so it is important to work with a kidney dietitian who can tailor recommendations to your specific situation.
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Protein management is one key dietary change. Your kidneys break down protein waste, so too much protein makes your kidneys work harder. People with Stage 3 kidney disease typically need to limit protein intake to about 0.8 grams per kilogram of body weight per day, which is less than the amount recommended for people without kidney disease. For a 154-pound person, this equals about 56 grams of protein daily. However, your needs may differ, so discuss your personal protein goal with your doctor or dietitian. Good protein sources that are gentler on kidneys include eggs, fish, and chicken in controlled portions.
Potassium control becomes increasingly important in Stage 3 kidney disease. Damaged kidneys cannot filter out excess potassium, which can accumulate in your blood and cause heart rhythm problems. High-potassium foods to limit include bananas, oranges, potatoes, tomatoes, spinach, and beans. You do not need to eliminate these foods entirely, but portion control matters. A kidney dietitian can help you understand which foods to limit and which lower-potassium alternatives you can enjoy instead, such as apples, grapes, bell peppers, and lettuce.
Phosphorus is another mineral your kidneys must regulate. Too much phosphorus can weaken your bones and cause calcium to deposit in blood vessels. Phosphorus is found in