Your kidneys are vital organs that perform many important functions in your body. They filter your blood, remove waste products and excess fluids, regulate your blood pressure, produce hormones, and maintain your electrolyte balance. However, sometimes your kidneys can get damaged or diseased due to various factors, such as diabetes, high blood pressure, infections, or medications. If left untreated, kidney problems can lead to serious complications, such as chronic kidney disease (CKD), kidney failure, or kidney stones.
Fortunately, you can prevent or detect kidney problems early by doing some simple blood tests that measure your kidney function. These tests can help you and your doctor monitor your kidney health and plan appropriate treatments if needed. In this article, we will explain what these tests are, what they mean, and how often you should do them.
What are the kidney function tests?
The most common and reliable test to assess your kidney function is the estimated glomerular filtration rate (eGFR). This test calculates how well your kidneys filter your blood based on your age, gender, size, race, and the level of creatinine in your blood. Creatinine is a waste product that comes from the normal breakdown of your muscles. If your kidneys are not working well, creatinine will build up in your blood and lower your eGFR.
The normal eGFR for an adult is between 90 and 120 mL/min/1.73 m2.
If your eGFR is lower than 60 mL/min/1.73 m2, it means that your kidneys are not functioning properly and you may have CKD. The lower your eGFR, the more severe your kidney damage is. According to the Kidney Disease Improving Global Outcomes (KDIGO), CKD can be classified into five stages based on the eGFR:
Stage 1: eGFR greater than 90 mL/min/1.73 m2
Stage 2: eGFR between 60 and 89 mL/min/1.73 m2
Stage 3a: eGFR between 45 and 59 mL/min/1.73 m2
Stage 3b: eGFR between 30 and 44 mL/min/1.73 m2
Stage 4: eGFR between 15 and 29 mL/min/1.73 m2
Stage 5: eGFR less than 15 mL/min/1.73 m2 or kidney failure
Another important test to check your kidney function is the urine albumin test. This test measures the amount of a protein called albumin in your urine. Albumin is normally present in your blood, but not in your urine. If your kidneys are damaged, they may leak albumin into your urine. This is called albuminuria or proteinuria, and it is a sign of kidney disease.
The higher the amount of albumin in your urine, the worse your kidney damage is.
The normal amount of albumin in your urine is less than 30 mg/g of creatinine. If your urine albumin is between 30 and 300 mg/g of creatinine, it means that you have microalbuminuria, which is a mild form of kidney damage.
If your urine albumin is more than 300 mg/g of creatinine, it means that you have macroalbuminuria, which is a severe form of kidney damage.
Besides the eGFR and the urine albumin tests, there are other blood tests that can help evaluate your kidney function.
These tests include:
Blood urea nitrogen (BUN): This test measures the amount of nitrogen in your blood that comes from the breakdown of urea, a waste product of protein metabolism.
If your kidneys are not working well, urea will accumulate in your blood and increase your BUN level.
The normal BUN level for an adult is between 7 and 20 mg/dL.
Serum creatinine: This test measures the amount of creatinine in your blood. As mentioned earlier, creatinine is a waste product that comes from the normal breakdown of your muscles.
If your kidneys are not working well, creatinine will build up in your blood and increase your serum creatinine level.
The normal serum creatinine level for an adult is between 0.6 and 1.2 mg/dL for men and between 0.5 and 1.1 mg/dL for women.
Electrolytes: These are minerals that are essential for your body's fluid balance, nerve and muscle function, and acid-base balance.
The main electrolytes that are measured in your blood are sodium, potassium, chloride, calcium, and phosphate.
If your kidneys are not working well, they may not be able to regulate the levels of these electrolytes in your blood, leading to either too high or too low levels. The normal ranges for these electrolytes are:
Sodium: 135 to 145 mEq/L
Potassium: 3.5 to 5.0 mEq/L
Chloride: 98 to 106 mEq/L
Calcium: 8.5 to 10.2 mg/dL
Phosphate: 2.5 to 4.5 mg/dL
Why are these tests important?
These tests are important because they can help you and your doctor monitor your kidney health and detect any problems early.
By doing these tests regularly, you can:
Prevent or delay the progression of kidney disease by identifying and treating the underlying causes, such as diabetes, high blood pressure, infections, or medications.
Avoid or minimize the complications of kidney disease, such as anemia, bone disease, cardiovascular disease, or fluid overload.
Plan for the best treatment options for kidney disease, such as medication, diet, lifestyle changes, dialysis, or kidney transplantation.
How often should you do these tests?
The frequency of doing these tests depends on your risk factors, your current kidney function, and your doctor's recommendations. In general, you should do these tests at least once a year if you have any of the following risk factors:
Diabetes
High blood pressure
Heart disease
Family history of kidney disease
Age over 60 years
Obesity
Smoking
Ethnicity (Indian/Asian, or Native American)
If you already have CKD, you should do these tests more often, depending on your stage of kidney disease and your doctor's advice.
The following table shows the suggested frequency of doing these tests for people with CKD:
Stage of CKD | eGFR | uACR | BUN | Creatinine | Electrolytes |
Stage -1 | Once a Year | Once a Yr | Once a Year | Once a Year | Once a Yr |
Stage-2 | Once a Yr | Once a Yr | Once a Yr | Once a Yr | Once a Yr |
Stage -3a | Every 6 Mnths | Every 6 Mnths | Every 6 Mnths | Every 6 Mnths | Every 6 Mnths |
Stage -3b | Every 3 Mnths | Every 3 Mnths | Every 3 Mnths | Every 3 Mnths | Every 3 Mnths |
Stage -4 | Every 1-2 Mnths | Every 1-2 Mnths | Every 1-2 Mnths | Every 1-2 Mnths | Every 1-2 Mnths |
Stage -5 | Every Mnth | Every Mnth | Every Mnth | Every Mnth | Every Mnth |
(Yr : Year , Mnths : Months, Mnth : Month)
How to prepare for these tests?
These tests are simple and easy to do. You do not need any special preparation for these tests, except for the following:
For the eGFR and the serum creatinine tests, you should avoid eating a lot of meat or protein-rich foods for 24 hours before the test, as they can increase your creatinine level and lower your eGFR.
For the urine albumin test, you should avoid exercising or having a fever for 24 hours before the test, as they can increase your urine albumin level and give a false positive result.
For the 24-hour urine test, you should collect all your urine in a container for a full day and night, starting from the second time you urinate in the morning and ending with the first time you urinate the next morning.
You should keep the container in a cool place and deliver it to the laboratory as soon as possible.
How to interpret the results of these tests?
Your doctor will explain the results of these tests to you and tell you what they mean for your kidney health. You should ask your doctor any questions you have about these tests and their results. You should also keep a record of your test results and compare them over time to see if there are any changes or trends in your kidney function. If your test results are abnormal or show signs of kidney damage, your doctor will advise you on the best course of action to treat your kidney problem and prevent further complications.
How to keep your kidneys healthy?
Besides doing these tests regularly, you can also take some steps to keep your kidneys healthy and prevent or delay kidney disease. Some of these steps are:
Control your blood sugar if you have diabetes, as high blood sugar can damage your kidneys over time.
Control your blood pressure if you have hypertension, as high blood pressure can put noextra strain on your kidneys and cause them to wear out faster.
Eat a healthy diet that is low in salt, fat, and sugar, and high in fruits, vegetables, and whole grains. This can help you maintain a healthy weight, lower your cholesterol, and prevent kidney stones.
Drink enough water and fluids to keep yourself hydrated and help your kidneys flush out waste and toxins from your body. Aim for at least 8 glasses of water a day, unless your doctor tells you otherwise.
avoid smoking and drinking alcohol, as they can harm your kidneys and increase your risk of kidney cancer.
Limit your intake of over-the-counter painkillers, such as aspirin, ibuprofen, or naproxen, as they can affect your kidney function and cause kidney damage if used for a long time or in high doses.
Get regular physical activity to keep your blood circulation and your muscles healthy, and to prevent obesity, diabetes, and high blood pressure.
Get checked for kidney infections, kidney stones, or urinary tract infections, as they can cause inflammation and scarring in your kidneys and impair their function.
Follow your doctor’s advice on taking any medications or supplements that may affect your kidney function, such as antibiotics, diuretics, or herbal remedies. Always read the labels and follow the instructions carefully.
If you have CKD, follow your doctor’s treatment plan and recommendations on diet, fluid intake, medication, dialysis, or kidney transplantation. You may also need to see a kidney specialist (nephrologist) and a dietitian to help you manage your condition and improve your quality of life.
By following these steps, you can keep your kidneys healthy and prevent or delay kidney disease. Remember, your kidneys are essential for your overall health and well-being, so do not neglect them. Do the simple blood tests regularly and take good care of your kidneys. They will thank you for it.
Author & Compiler
Sharad Mishra
Clinical Pharmacist, Lab Diagnostic Expert, Lab Franchise Consultant, Diet Psychologist, Believe in Simplicity & on a Mission to Improve Lives
Bsc, B Pharmacy, ICMS- Sydney- Competitive Edge in Management, Professional Diploma in Nutrition, Professional Diploma in Health & Fitness (EQF Level V), Diploma in Sports Nutrition, IIT Madras Certificate in Electrocardiogram- Interpretation & Application in Clinical Practice, IIT Kanpur Diploma in Introduction to Advanced Cognitive Processes, Certificate in ISO 15189-2022- Medical Laboratories Quality Assurance & Competence CPD Certified - Looks after Lab Franchisee Model of Ranbaxy lab
Author is having more than 19 years of experience in Lab Diagnostic, Operations, Lab Equipment OEM & Pharmaceutical Operations, Over the course of his corporate career, Sharad Mishra has written various articles on Lab test interpretation, Sales & Marketing, as well as on Drug Delivery module, apart from such articles and short notes, Sharad Mishra has also started its Youtube Channel (http://www.youtube.com/c/SKMHealthMythology), which talks about various aspects right from Covid 19 pandemic to health & some interesting facts about mythology.
Sharad Mishra is also a licensed pharmacist with experience & interest in infectious disease, metabolic diseases i.e. diabetes, hypertension education & management. He has a passion for personalized patient care and believes that education is essential to living a healthy life. His goal is to motivate individuals to find ways to manage their chronic conditions & also started online learning programs to tackle & reverse metabolic issues i.e. SugarSolve, PcosSolve & FatSolve , these programs are designed to reverse diabetes, PCOS & weight issue without medicines on the principles of Human Physiology.
Work aside, Sharad Mishra is a photographer and lives his passion for nature photography.
