All you need to know about your kidneys and how to keep them healthy

When we talk about our health, there is a tendency to focus on issues such as cardiovascular disease and liver disease. 

These are big, public health problems about which people are usually very aware, particularly with regards to the role that lifestyle factors like smoking, a poor diet, alcohol intake and lack of exercise have in causing these diseases. In contrast, the kidneys are often overlooked. However, kidney disease is actually very common with around 3 million people in the UK estimated to be suffering from it. Many of these people will have no idea that there is a problem because kidney disease often causes no symptoms until a very late stage. 

They are found around the back of your body, just above your waistline in the angle between your rib cage and your pelvis. They are about 10-12 cm in length and, as you might guess, they are the shape of a kidney bean. 

They carry out many important functions. Perhaps their most notable function is the removal of waste products from the blood and the production of urine, but they are also involved with the regulation of blood pressure, the maintenance of blood electrolyte levels, the production of red blood cells and the metabolism of vitamin D and calcium. 

When the kidneys aren’t functioning properly, you can therefore develop further problems in all of these areas. 

There are many reasons why the function of your kidneys might deteriorate. The most common is simply ageing; we tend to see a slow drift downwards in kidney function as people get older and a degree of impairment is fairly normal in elderly people. There are some inherited conditions that can cause kidney disease, some infections that will damage the kidneys, and some medications that can harm them, including common medications such as ibuprofen.

But the biggest threats to our kidneys are actually the same as those that cause heart attacks and strokes. We commonly see evidence of kidney disease due to high blood pressure, diabetes, smoking, obesity, and raised cholesterol. To look after your kidneys, it is therefore very important to identify these issues and tackle them before too much damage is done. 

In its later stages, kidney disease can cause a wide range of symptoms such as tiredness, fluid retention, shortness of breath, itching, nausea and loss of appetite, but most people with the disease will actually have no symptoms. Fortunately, detecting disease is very straightforward with a blood test.

Because the kidneys are so important, testing the function is one of the most common tests requested.

The main measure of health that we use is a measure of how effectively your kidneys can process your blood known as the ‘estimated glomerular filtration rate’ or eGFR. Essentially, the eGFR is a score of how well your kidneys are working. A score above 60 is usually considered healthy unless there are other markers such as the presence of blood or protein in your urine. A score consistently below 60 would suggest a diagnosis of ‘chronic kidney disease’ or CKD.

As suggested at the top of the article, CKD is very common. It is important to note that, whilst many people think that ‘chronic’ means ‘severe’, in medicine it means anything that is long lasting. This means that you can have mild CKD.

At One Day Tests we provide two different types of Kidney function test.

Our Kidney Function Blood Test, tests for 4 biomarkers in the blood; Sodium, Urea, Creatinine and eGFR.

Our Advanced Kidney Function Blood Test is the more comprehensive version that tests for 8 different biomarkers in the blood. The 4 additional markers tested are; Albumin, total protein, Chlorine and Potassium.

A biomarker is a measurable indicator that provides valuable information about your health. Each biomarker in the blood test is analysed and will be scored against a specific range.

If CKD is identified this is usually not a cause for panic, but it should definitely be a prompt to make sure that you are doing everything possible to look after your kidneys. This means making sure:

• Your blood pressure is well controlled
• High cholesterol is treated
• Diabetes is identified and well managed
• You stop smoking, drink alcohol within recommended limits, and maintain a healthy weight

Your doctor will also make sure not to prescribe you any medication that might further damage.

If your eGFR is below 30, your doctor may suggest that you see a kidney specialist to make sure you have none of the more unusual causes of kidney disease and to help plan your future care. An eGFR below 15 represents severe CKD and it is below this level that you may need to receive treatment with dialysis.

Once a problem has been identified, then it is also important to monitor the health of your kidneys. The frequency of monitoring depends on the degree of CKD. If you have an eGFR between 45 and 60 then the National Institute of Health and Care Excellence recommend having at least an annual blood test. Those with an eGFR of between 15 and 45 should have it checked at least 6 monthly. People with an eGFR below 15 will need more frequent monitoring but will usually be under the care of a kidney specialist. 

COMMON EARLY WARNING SIGNS PEOPLE MAY NOTICE

Although early kidney disease often causes no symptoms, some people may notice subtle changes as kidney function declines.

Fatigue, low energy, weakness, or difficulty concentrating can occur when waste products are no longer efficiently removed from the blood. A build up of urea and other toxins can affect both physical and mental energy levels.

Sleep disturbance is another possible sign. When toxins remain in the bloodstream instead of being filtered out by the kidneys, they can interfere with normal sleep patterns.

Dry or itchy skin may develop when kidney disease affects the balance of minerals in the body. This can occur alongside changes in calcium and phosphate levels.

Changes in appetite, nausea, or a reduced desire to eat can also be linked to toxin build up. Some people experience a metallic taste in the mouth or a general feeling of being unwell.

Muscle cramps can occur when kidney disease disrupts electrolyte balance. The kidneys play a key role in regulating levels of sodium, potassium, and calcium, and imbalances can affect muscle and nerve function.

Headaches may occur as a result of high blood pressure, anaemia, or fluid and electrolyte disturbances linked to declining kidney function.

URINE CHANGES THAT CAN BE AN EARLY SIGN

Changes in urine are often one of the earliest clues that the kidneys may not be working properly.

Needing to urinate more frequently, especially at night, can occur when the kidneys struggle to concentrate urine. On the other hand, passing less urine than usual can also be a warning sign and should be assessed by a doctor.

Blood in the urine has several possible causes. It may be due to something relatively simple such as a urinary infection or kidney stones, which are often painful. Painless blood in the urine can sometimes be linked to kidney disease, bladder conditions, or more serious underlying problems and should always be checked.

Foamy or frothy urine is an important sign that protein may be leaking into the urine. This can happen even before blood tests show abnormal kidney function and may be an early indicator of kidney damage.

Not all urine changes are caused by kidney disease. Dehydration can reduce urine output, while diabetes can increase urine volume and thirst. Prostate problems in men can lead to frequent urination and difficulty emptying the bladder. Because of this overlap, urine changes should always be interpreted alongside blood tests and clinical assessment.

SWELLING AND FLUID RETENTION SIGNS

Swelling is a more noticeable sign that kidney function may be impaired. It typically affects the feet, ankles, hands, abdomen, or the area around the eyes.

There are several reasons why swelling occurs in kidney disease. When the kidneys are unable to remove excess fluid efficiently, water is retained in the body. In addition, damaged kidneys may leak albumin into the urine. Albumin helps keep fluid inside blood vessels, and low levels can cause fluid to leak into surrounding tissues.

Kidney disease can also lead to sodium retention, which causes the body to hold onto more water. The combination of these effects results in visible swelling.

It is important to note that swelling can also be caused by other conditions, including heart failure, liver disease, problems with leg veins, or certain medications. Any new or worsening swelling should be assessed by a doctor to determine the underlying cause.

BREATHLESSNESS AND OTHER LATER SIGNS

Shortness of breath is usually a later sign of kidney disease and suggests more advanced involvement.

One cause is anaemia. The kidneys produce a hormone called erythropoietin, which helps stimulate red blood cell production. When kidney function declines, this hormone is produced in lower amounts, leading to anaemia and reduced oxygen delivery to the body.

Fluid overload can also cause breathlessness. Excess fluid may build up in the lungs when the heart is unable to cope with the increased volume. This can cause breathlessness on exertion or when lying flat.

Sudden onset breathlessness should always be treated as a medical emergency. Gradual breathlessness developing over weeks or months should still be assessed promptly by a healthcare professional.

WHAT DOES IT MEAN WHEN KIDNEY FUNCTION IS LOW?

When a kidney function test is low, it means your kidneys are filtering less blood than expected. The main measurement used is eGFR, or estimated glomerular filtration rate. A healthy eGFR is typically above 90. An eGFR between 60 and 89 may suggest early changes, while values below 60 can indicate reduced kidney function.

Low results can be temporary or long-term. For example, dehydration or certain medications can reduce kidney function for a short period. However, consistently low readings over several tests may point to chronic kidney disease, where kidney performance gradually declines over time.

Doctors often repeat testing over several months to confirm whether the problem is ongoing. A single low result isn’t always a cause for alarm, but it’s an important signal to monitor your kidney health closely.

NORMAL EGFR RANGES AND WHAT THEY MEAN

There is no single normal kidney function result that applies to everyone. eGFR results are interpreted using ranges that help classify kidney health and identify chronic kidney disease if present.

An eGFR above 90 is considered normal kidney function. However, if blood or protein is detected in the urine, this may still be classified as chronic kidney disease stage 1.

An eGFR between 60 and 89 is generally considered satisfactory and is very common, particularly in people over the age of 60. If urine abnormalities are present alongside this range, it may be classified as chronic kidney disease stage 2.

An eGFR between 30 and 59 indicates reduced kidney function and is classed as chronic kidney disease stage 3. This stage is often divided into stage 3a, which ranges from 45 to 59, and stage 3b, which ranges from 30 to 44.

An eGFR between 15 and 29 is classified as chronic kidney disease stage 4 and represents significant kidney impairment. People at this stage are usually reviewed by a kidney specialist.

An eGFR below 15 is classified as chronic kidney disease stage 5, also known as end stage kidney disease. At this point, dialysis may be considered depending on overall health and symptoms.

Although many people know little about it, CKD is very important. If your kidneys aren’t functioning properly, it can cause a huge range of problems from anaemia to osteoporosis but, beyond that, chronic kidney disease is itself a risk factor for heart attacks and strokes. It is therefore best to identify the problem early and start making changes that will prevent it getting worse.

One Day Tests offer you the power to monitor and understand your health like never before. Whether it’s for routine health checks, managing a chronic condition, or just staying informed about your body, our range of blood tests provides the convenience, accuracy, and peace of mind you deserve.

Whether you choose to visit a clinic for your blood work or opt for the convenience and comfort of using our at-home blood test kits , we ensure a service that is not only dependable but also tailored to suit your preferences.

For additional assistance, guidance or queries regarding our custom panels, do not hesitate to get in touch. Our team is here to help you with any questions and provide you with the information you need. You can contact us at 0845 527 07 67, send an email to hello@onedaytests.com, or reach out to us via WhatsApp.