Testing for Kidney Function

What is kidney disease?

The kidneys are two bean-shaped organs. Each kidney is about the size of a fist. Your kidneys filter excess water and waste from your blood and make urine. Kidney disease means that your kidneys are damaged and cannot filter your blood the way they should.

If you have diabetes or high blood pressure, you are at greater risk of developing kidney disease. If you develop kidney failure, treatment includes a kidney transplant or dialysis. Other kidney problems include acute kidney injury, kidney cysts, kidney stones, and kidney infections.

What alerts you to the need for a testing for kidney function?

Kidney disease can get worse over time as waste and fluid build up in your body. The following are some warning signs.

There are changes in your urine. You may be urinating more or less than normal. Or you may notice a change in color or that your urine is frothy. This means that protein is leaking out of your kidneys. Blood in your urine is another sign.

Dry and itchy skin. This happens when your kidneys are no longer able to balance the minerals and nutrients in your blood.

Swelling. Your kidneys help balance the amount of sodium (salt) in your body. When they don't work well, your body develops extra sodium (salt). This can cause the skin around your ankles and feet to puff up. You may also notice it in your hands or around your eyes.

Upset stomach. Waste buildup in your blood can cause nausea and loss of appetite.

Fatigue. Your kidneys produce a hormone that tells your body to make red blood cells that carry oxygen throughout your body. If they aren't working properly, this can't be done and you may have a health problem called anemia. You may feel tired, even after you've rested. The quality of your sleep may also be affected.

What is testing for kidney function?

Blood testing for kidney function

Because your kidneys remove waste, toxins and excess fluid from your blood, a blood test can also be used testing for kidney function. The blood testing for kidney function will show how well your kidneys are working and how quickly they are removing waste products. Here are some of the blood tests used.

Creatinine testing for kidney function. A creatinine blood testing for kidney function measures the amount of creatinine in your blood. If your kidneys are not working as well as they should, your serum creatinine level will go up. Your normal level will depend on your gender, age, and the amount of muscle mass in your body.
Typically, a creatinine level above 1.2 in women and 1.4 in men may be a sign that something is wrong with your kidneys. If your serum creatinine test results are higher than normal, other tests are needed.

Urea testing for kidney function. This testing for kidney function measures the level of urea in your blood. Urea is a waste product that your body produces from the breakdown of protein in the food you eat. Healthy kidneys filter urea nitrogen out of your blood and out of your body through your urine. This process helps keep your urea levels in the normal range. The normal level of urea will depend on your age and any other health conditions you may have, but is usually between 7 and 20. If your urea levels are higher than normal, this may be a sign that your kidneys are not working as well as they should. As kidney disease progresses, your urea levels will rise.
If your urea levels show signs of kidney disease, your doctor will use your test results, as well as other tests, to determine the treatment plan that is best for you.

Glomerular filtration rate (GFR). Glomerular filtration rate is a measure of how well your kidneys remove waste, toxins and excess fluid from your blood. Your serum creatinine level, age and gender are used to calculate your GFR number. Like other kidney tests, your normal GFR number will depend on your age and gender. If your GFR is low, your kidneys may not be working as well as they should. As kidney disease progresses, your GFR will drop. Your test results may mean the following.

If your GFR number is 60 or higher and your urine albumin test is normal, you are in the normal range. However, you still need to discuss with your doctor when you should be tested again.
If your GFR number is below 60, this may mean you have kidney disease. You will want to discuss with your doctor what treatment options are best for you.
If your GFR number is below 15, this may mean that your kidneys are failing. If your results show kidney failure, you will likely need dialysis or a kidney transplant. You should know that if your GFR level stays below 20 for 6-12 months, your doctor may consider you for a kidney transplant as a precautionary measure.

Why do I need a testing for kidney function?

If you are a diabetic and have high blood pressure, you are at a higher risk of developing chronic kidney disease. Your doctor may recommend that you have one or more testing for kidney function to check your kidney health. Kidney disease can sometimes be difficult to detect, and the sooner you know the health of your kidneys, the sooner you can take steps to protect them. Maybe you think your kidneys are healthy, but you don't really know your health and understand how testing for kidney function work and what your results might mean.

Chronic kidney disease (CKD) is a condition in which, over time, the kidneys become damaged and cannot filter blood as well as they should. Diabetes is a major cause of CKD and usually doesn't cause any symptoms until your kidneys are severely damaged.

The good news is that if you catch and treat kidney disease early, you may be able to keep CKD from getting worse and prevent other health problems, such as heart disease. But the only way to know how well your kidneys are working is to have your kidney function tested ahead of time.

If you have diabetes, you know how important it is to prevent complications like CKD. Your doctor will want to check your kidney health, usually by doing a testing for kidney function with your urine and blood.

What is the urine testing for kidney function?

Urine testing for kidney function

One of the earliest signs of kidney disease is protein leaking into your urine. To check for protein in your urine, your doctor will order a urine test. There are two types of urine tests that can check your protein levels.

An infiltration urine test. This test is usually done as part of an overall urinalysis, but it can also be used as a quick test to look for albumin in the urine. It does not provide an accurate measurement of albumin, but it will let your doctor know if your albumin level is normal. A measuring cylinder (a chemically treated paper) is placed in the urine sample you provide and will change color if the albumin level is too high. If your albumin level is not normal, your doctor may want to do further tests.

Urine albumin to creatinine ratio (UACR). This test measures the amount of albumin and compares it to the amount of creatinine (a waste product from normal muscle wear in the body) in your urine. the UACR test lets your doctor know how much albumin has entered your urine in a 24-hour period. A urine albumin test result of 30 or more may mean kidney disease.

The urine test may be repeated once or twice to confirm the results. If you do have kidney disease, the amount of albumin in your urine helps your doctor know which treatment is best for you. A constant or decreasing albumin level in your urine means that your treatment is working.

What other tests you may need?

Monitor your blood pressure or suggest other tests, such as imaging or biopsy, to testing for any kidney function problems.

Blood pressure test. Because high blood pressure is a major cause of kidney disease and kidney failure, your doctor will want to monitor your blood pressure. If you have CKD, it's important to control high blood pressure, blood sugar and cholesterol levels - all factors that increase the risk of heart disease and stroke.

Imaging tests. These tests are used to get images of your kidneys to look for any problems or damage. Imaging tests allow your doctor to see how well the blood is flowing to your kidneys or if there are any blockages or narrowings in the blood vessels.

Kidney biopsy. A kidney biopsy is a procedure in which a small piece of kidney tissue is removed and examined under a microscope for signs of damage or disease. This is done by inserting a fine needle into the skin.

What can I do to stay healthy after my testing for kidney function?

You can help reduce your risk of developing CKD or prevent it from getting worse by eating a healthy diet, being active, and keeping your blood pressure and cholesterol levels within your target range. If you are at risk of developing CKD, make sure you take care of your kidneys. If you have diabetes, get tested for kidney disease once a year. Having regular testing for kidney function gives you the best chance of detecting and treating CKD early.

Make kidneys healthy food choices

A diet conducive to kidney health should limit sodium, cholesterol and fat, focusing instead on fruits, vegetables, whole grains, low-fat dairy products and lean meats (seafood, poultry, eggs, beans, nuts, seeds and soy products), and people who have been diagnosed with CKD may also need to limit certain other nutrients.

Here are a few ways to adjust your diet to keep your kidneys healthy
1. Good dietary distribution is good for kidneys healthy
As a general rule of thumb, follow the method at each meal. Fill about half of your plate with vegetables and fruits, a quarter with lean protein and a quarter with whole grains.

2. Limit your salt intake for your kidneys healthy
Sodium sneaks into all sorts of places you wouldn't think possible, especially packaged foods like soups and breads. Limiting your sodium intake can help control your blood pressure. According to the 2020-2025 Dietary Guidelines for Americans issued by the U.S. Food and Drug Administration, aim for 2,300 milligrams per day - that's about 1 teaspoon of table salt.

If you are at risk for high blood pressure or already have high blood pressure, Maruschak recommends following a low-sodium diet - specifically the Dietary Approaches to Stop Hypertension (DASH) eating plan. Try these tips to control your sodium, too.

Limit ordering takeout and eating at restaurants.
Cook at home with whole, unprocessed foods. When you cook at home with fresh ingredients, you can control exactly how much sodium (and fat) is in each bite.
Use condiments creatively. Maruschak recommends avoiding salt when cooking or at the table. Instead, use spices, herbs, lemons and other sodium-free condiments.
Check packaging. Any prepared food that has sodium at or above your daily value is considered high in sodium. Whenever possible, choose soups, frozen meals and other packaged foods that are labeled reduced sodium, low sodium or no salt.
Rinse canned foods before eating them. This helps remove excess sodium.

3. Watch your protein intake for your kidneys healthy
When you eat protein, your body produces waste products that are filtered through your kidneys. While protein is an important part of a healthy diet, eating more protein than you need may cause your kidneys to work harder. While more research is needed on the effects of a high-protein diet on overall kidney health, if you already have CKD, your doctor may recommend a low-protein diet.

Whether you have been diagnosed with CKD or not, choosing healthier protein sources and watching your portion sizes can help. Good sources of protein include:

• Lean meat, fish or skinless poultry (a serving size of 2 to 3 ounces, or about the size of a deck of playing cards)
• Eggs
• Dairy products (a serving size of yogurt and milk is ½ cup, while a serving size of cheese is 1 ounce - about the size of your two thumbs combined)
• Beans, chickpeas, lentils, peas (one serving is ½ cup)
• Nuts (one serving is 1/4 cup)

4. Choosing complex carbohydrates is better for your kidneys healthy

Carbohydrates are your body's primary source of energy, and those naturally occurring in fresh foods are full of fiber, support heart and gut health, and keep your blood sugar levels stable. However, simple carbohydrates - such as the sugar added in desserts, sweetened beverages and many packaged foods - can raise blood sugar and increase the risk of obesity, type 2 diabetes and heart disease.

As part of an overall healthy diet, you should limit sweets and foods with added sugar (check labels - they're found in many surprising places, such as fruit yogurt). Healthier carbohydrate options include whole grains, fruits, vegetables, beans and lentils.