Kidney Function Test

Kidneys are your body’s filtration system

You have two kidneys on either side of your spine that are each approximately the size of a human fist. They’re located posterior to your abdomen and below your rib cage. Your kidneys play several vital roles in maintaining your health. One of their most important jobs is to filter waste materials from the blood and expel them from the body as urine.

When functioning normally, your kidneys can filter up to 250 pints of blood each day, producing 3 pints of of urine. This helps prevent waste buildup in the body. It also helps keep electrolytes, such as sodium, phosphate, and potassium at stable levels.

The kidneys also help control the levels of water and various essential minerals in the body. In addition, they’re critical to the production of:

  • vitamin D
  • red blood cells
  • hormones that regulate blood pressure

If your doctor thinks your kidneys may not be working properly, you may need kidney function tests. These are simple blood and urine tests that can identify problems with your kidneys.

You may also need kidney function testing done if you have other conditions that can harm the kidneys, such as diabetes or high blood pressure. They can help doctors monitor these conditions.

Symptoms of kidney problems

Symptoms that may indicate a problem with your kidneys include:

  • unexplained body/abdominal swelling
  • swelling of the hands, feet, ankles or wrists
  • high blood pressure
  • blood in the urine
  • frequent urges to urinate
  • difficulty beginning urination
  • painful urination
  • foamy urine
  • mid-back pain or lower back pain near the kidneys
  • fatigue or trouble sleeping
  • loss of appetite
  • nausea or vomiting

A single symptom may not mean something serious. However, when occurring simultaneously, these symptoms suggest that your kidneys aren’t working properly. Kidney function tests can help determine the reason.

Early intervention is vital to preventing further kidney damage.

What causes kidney damage?

Chronic kidney disease is usually caused by other conditions that put a strain on the kidneys. Often it’s the result of a combination of different problems including:

  • high blood pressure – over time, this can put strain on the small blood vessels in the kidneys and stop the kidneys working properly
  • diabetes – too much glucose in your blood can damage the tiny filters in the kidneys
  • high cholesterol – this can cause a build-up of fatty deposits in the blood vessels supplying your kidneys, which can make it harder for them to work properly
  • kidney infections
  • glomerulonephritis – kidney inflammation
  • polycystic kidney disease – an inherited condition where growths called cysts develop in the kidneys
  • blockages in the flow of urine – for example, from kidney stones that keep coming back, or an enlarged prostate
  • long-term, regular use of certain medicines – such as lithium and non-steroidal anti-inflammatory drugs (NSAIDs)

The Kidney Function test

To test your kidney function, our test screens for the following:

  1. Glomerular Filtration Rate
  2. Creatinine
  3. Bicarbonate
  4. Chloride
  5. Potassium
  6. Sodium
  7. Urea (BUN)

Glomerular Filtration Rate (GFR)

Your kidneys are your body’s main filtration system. They remove waste products from your blood and excrete them via your urine. Glomeruli are the small filters inside your kidneys. If your kidneys aren’t working properly, your glomeruli won’t filter as efficiently.

The GFR test can indicate how well your kidneys are functioning or how well a particular treatment may be working.

There’s a specific formula used to calculate GFR which will require you to provide your age, sex, race, height and weight.

The lower your GFR results, the more damage your kidneys have. The GFR can determine the amount and stage of kidney damage you have:

  • Stage 1: minimal or no loss of kidney function (GFR of 90 or above)
  • Stage 2: mild loss of kidney function (GFR of 60 to 89)
  • Stage 3: moderate loss of kidney function (GFR of 30 to 59)
  • Stage 4: severe loss of kidney function (GFR of 15 to 29)
  • Stage 5: kidney failure (GFR of 15 or below)

These are guidelines and a slightly different scale may be used.

Serum creatinine test

A creatinine blood test measures the level of creatinine in the blood. Creatinine is a waste product that forms when creatine, which is found in your muscle, breaks down. Creatinine is one of the substances that your kidneys normally eliminate from the body.

High levels of creatinine may indicate that your kidney is damaged and not working properly.

Some drugs may increase your creatinine levels without causing kidney damage and interfere with your test results. These include cimetidine, NSAIDs (aspirin or ibuprofen), chemotherapy drugs, certain antibiotics. Take this into consideration when interpreting your test results.

Blood urea nitrogen (BUN)

A blood urea nitrogen (BUN) test is used to determine how well your kidneys are working. It does this by measuring the amount of urea nitrogen in the blood. Urea nitrogen is a waste product that’s created in the liver when the body breaks down proteins. Normally, the kidneys filter out this waste, and urinating removes it from the body.

BUN levels tend to increase when the kidneys or liver are damaged. Having too much urea nitrogen in the blood can be a sign of kidney or liver problems.

While a BUN test measures the amount of urea nitrogen in the blood, it doesn’t identify the cause of a higher or lower than average urea nitrogen count.

Higher BUN levels can indicate:

  • heart disease
  • congestive heart failure
  • a recent heart attack
  • gastrointestinal bleeding
  • dehydration
  • high protein levels
  • kidney disease or kidney failure
  • dehydration
  • obstruction in the urinary tract
  • stress

Lower BUN levels can indicate:

  • liver failure
  • malnutrition
  • severe lack of protein in the diet
  • overhydration

Abnormal BUN levels don’t necessarily mean you have a kidney condition. Certain factors, such as dehydration, pregnancy, high or low protein intake, steroids, and aging can impact your levels without indicating a health risk.

Common medications, including large doses of aspirin and some types of antibiotics, can also increase your BUN. So you may need to stop certain drugs for a few days before the test (but be sure to complete any course of antibiotics you’re on).


We all need bicarbonate (a form of carbon dioxide) in our blood. It keeps our blood from becoming too acidic. Low bicarbonate levels in the blood are a sign of metabolic acidosis (the buildup of acid in the body due to kidney disease or kidney failure as your kidneys are unable to adequately remove the acid from your blood). Low bicarbonate levels can make kidney disease worse.

Metabolic acidosis can cause:

  • Increased bone loss (osteoporosis): Metabolic acidosis can lead to a loss of bone in your body. This can lead to a higher chance of fractures in important bones like your hips or backbone.
  • Progression of kidney disease: Metabolic acidosis can make your kidney disease worse.  Exactly how this happens is not clear. As acid builds up, kidney function lowers; and as kidney function lowers, acid builds up. This can lead to the progression of kidney disease.
  • Muscle loss:Albumin is an important protein in your body that helps build and keep muscles healthy. Metabolic acidosis lowers the amount of albumin created in your body, and leads to muscle loss, or what is called “muscle wasting.”
  • Endocrine disorders: Metabolic acidosis interferes with your body’s ability to maintain normal functions of your endocrine system (the collection of glands that produce hormones). This can cause your body to build a resistance to insulin (the hormone in your body that helps keep your blood sugar level from getting too high or too low). If left untreated for too long or not corrected in time, it can lead to diabetes.


You may have heard of electrolytes (minerals in your body with an electrical charge) and the role they play in keeping you hydrated and healthy. One of the most important of these electrically charged minerals is chloride. It works with other electrolytes, such as sodium and potassium, to help balance acids and bases (the opposite of acids)in your body.

Chloride helps move fluid in and out of your cells. So if your chloride levels drop, you can become sick and dehydrated. If your levels are too high, it often means your kidneys aren’t working properly. (Diabetes can sometimes cause chloride levels to increase.)

Some hormones/medications may also increase chloride levels: cortisone (used to ease pain and inflammation), oestrogen,  ammonium chloride (used to treat people with low chloride in the blood and a condition called metabolic alkalosis), nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin and ibuprofen.

The normal range for chloride in your blood is between 96 and 106 milliequivalents per liter (MEq/L). Chloride levels above 106 could point to kidney problems, such as renal tubular acidosis (when your kidneys aren’t removing enough acids from your blood and into your urine).

Low levels have several other possible causes, including common, temporary problems such as vomiting and dehydration. Among the more serious causes are:

  • Congestive heart failure (when your heart muscle is weakened and can’t pump blood to your body as it should)
  • Burns
  • Addison’s disease (when your adrenal glands don’t make enough of certain hormones)
  • Metabolic alkalosis (low potassium and chloride in the blood)
  • Hyperaldosteronism (a condition that can cause high blood pressure and weakness)
  • Chronic lung disease


Sodium is one of the body’s three major electrolytes (potassium and chloride are the other two). Electrolytes control the fluids going in and out of the body’s tissues and cells. Salt  is a major source of electrolytes. Sodium contributes to:

  • Regulating blood pressure and blood volume
  • Helping transmit impulses for nerve function and muscle contraction
  • Regulating the acid-base balance of blood and body fluids

 Although sodium is essential for the body functions listed above, too much sodium can be harmful for people with kidney disease because your kidneys cannot eliminate excess sodium and fluid from your body.

As sodium and fluid build up in your tissues and bloodstream, your blood pressure increases and you begin to feel unwell.

High blood pressure can cause more damage to unhealthy kidneys. This damage further reduces kidney function, resulting in even more fluid and waste build up in the body.

Cooking “real food” with salt is not the problem. The problem is eating too much hidden salt found in highly processed foods, frozen foods and restaurant meals, especially condiments and sauces. This simple step can help lower your sodium. Be wary of “low-sodium” options as these tend to be higher in potassium which is to be avoided in a renal diet. (A renal diet is one that is low in sodium, phosphorous, and protein).


People with chronic kidney disease or kidney damage have a high risk for a condition called hyperkalemia (high levels of potassium in the blood), due in part to the effects of kidney dysfunction. They’re typically unable to regulate potassium efficiently.

Hyperkalemia is unpredictable and can be life-threatening. It can cause serious heart problems and sudden death. There are often no warning signs, meaning a person can have high potassium without knowing it. Hyperkalemia requires immediate medical care.

High potassium levels usually develop slowly over weeks or months. This can lead to feelings of fatigue or nausea. If your potassium spikes suddenly, you may experience difficulty breathing, chest pain, or heart palpitations and should seek medical assistance immediately.

One of the best ways to reduce potassium buildup is to make dietary changes. To do that, you’ll need to learn which foods are high in potassium and which are low. Be sure to do your research and read the nutritional labels on your food.

Although reducing intake of potassium-rich foods is important for those on potassium restricted diets, keeping total potassium intake under the limit set by your healthcare provider, which is typically 2,000 mg of potassium per day or less, is most important.

Depending on your kidney function, you may be able to include small amounts of foods higher in potassium in your diet.

Order a Kidney Function Test Kit

Order a Kidney Function Home Test Kit. Our Kidney Function home blood test kit checks critical electrolytes, minerals & proteins in your blood.

Waste product accumulation and fluid imbalances can indicate that your kidneys are not functioning properly and can cause damage to your body or a potentially life-threatening situation.

Get the convenience of home testing with the reassurance of professional clinical analysis. Your results are delivered quickly and securely online.

This Kidney Function Test is advised if you:

  • eat a high protein diet;
  • have a family history of kidney problems;
  • have diabetes, or impaired glucose tolerance;
  • have kidney disease;
  • have kidney stones;
  • have recently experienced an acute injury;
  • have, or have had, high blood pressure;
  • regularly take anti-inflammatory medication (including aspirin & ibuprofen);
  • suffer from urinary tract infections (UTIs);
  • want the convenience of home testing without waiting for a GP appointment;
  • need a high quality, clinically accredited test done in a professional clinical laboratory.

What is tested?

  1. Glomerular Filtration Rate
  2. Creatinine
  3. Bicarbonate
  4. Chloride
  5. Potassium
  6. Sodium
  7. Urea (BUN)

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SYMPTOMS: unexplained body/abdominal swelling; swelling of the hands, feet, ankles or wrists; high blood pressure; blood in the urine; frequent urges to urinate; difficulty beginning urination; painful urination; foamy urine; mid-back pain or lower back pain near the kidneys; fatigue or trouble sleeping; loss of appetite; nausea or vomiting.

May 7, 2020