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Your kidneys are vital organs that quietly work around the clock to remove waste and keep your body in balance. One of the most important indicators of how well your kidneys are functioning is your eGFR, or estimated glomerular filtration rate. Whether you’re managing a chronic condition or simply monitoring your health, understanding your eGFR can offer early clues about kidney health, before symptoms even appear. But what exactly is eGFR, what do different values mean, and how can you improve it?
Table of Contents
- What is eGFR?
- What is a good eGFR value?
- The causes of an eGFR value that is too low
- What does a low eGFR value mean?
- Symptoms of an eGFR value that is too low
- eGFR Testing
- How can I increase my eGFR?
- Summary
What is eGFR?
eGFR stands for estimated glomerular filtration rate and reflects how well the kidneys filter blood. It is calculated based on blood creatinine levels, a waste product produced when muscles break down energy. Healthy kidneys continuously filter creatinine from the blood, removing it through urine. When kidney function declines, creatinine builds up in the blood. The eGFR result estimates how much blood the kidneys filter per minute and serves as an important indicator of kidney function.
What is the difference between eGFR and creatinine?
Creatinine is a waste product produced by muscles and filtered out of the blood by the kidneys. eGFR is a calculated value based on creatinine levels, age, sex, and other factors, and provides an estimate of how well the kidneys are filtering blood.
Why is eGFR important?
The kidneys play a vital role in removing waste products from the body through urine. When kidney function declines, waste can build up in the blood, leading to serious health issues. A low eGFR can indicate kidney damage or reduced kidney function, which may require further investigation or treatment.
eGFR is particularly important for people with risk factors such as:
- Diabetes
- High blood pressure
- Family history of kidney disease
- Older age
- Use of medications that affect kidney function
What is a good eGFR value?
The value of the filtration rate differs from person to person. For example, in a healthy individual, the result of an eGFR test is more than 90 milliliters per minute. However, the speed decreases as you get older. People with an advanced age therefore usually have a lower eGFR (an average of 30 to 45 milliliters per minute). This is not seen as an abnormal value due to age.
Which eGFR value is critical?
A GFR value below 60 mL/min/1.73 m² is considered critical, as it may indicate chronic kidney disease. A lower eGFR value corresponds to different stages of kidney disease severity (Netherlands General Practitioners Association, 2019):
| Stage | eGFR (mL/min/1.73 m²) | Description |
|---|---|---|
| G1 | 90 or higher | Normal kidney function (if no other signs of disease) |
| G2 | 60 – 89 | Mild decrease; usually no symptoms |
| G3a | 45 – 59 | Mild to moderate decrease |
| G3b | 30 – 44 | Moderate to severe decrease |
| G4 | 15 – 29 | Severe decrease; may require specialist care |
| G5 | Below 15 | Kidney failure; possible need for dialysis or transplant |
The causes of an eGFR value that is too low
There are various causes of an eGFR value that is too low. One reason can be natural causes, because with age it is normal for kidney function to decline. Black people also naturally have a lower eGFR. However, there are many possible reasons why eGFR may be lower than normal. Some common causes include:
- Chronic kidney disease
- Diabetes
- High blood pressure
- Kidney infections (e.g., glomerulonephritis)
- Polycystic kidney disease
- Dehydration (temporary)
- Certain medications or toxins
In older adults, lower eGFR values may reflect age-related decline in kidney function, and may not always indicate disease.
What does a low eGFR value mean?
An eGFR value that is too low can mean that the kidneys no longer function optimally, so that the blood is not properly purified. This gives waste products the opportunity to accumulate in the body. Kidneys that no longer function optimally are often unable to properly regulate the fluid balance in the body (Albert Schweitzer Hospital). Furthermore, reduced kidney function can cause problems with bone health. That’s because the kidneys are less able to make vitamin D, which makes bones weaker and possibly more likely to break. People with a lowered eGFR have a higher risk of chronic kidney disease (CKD) progressing to kidney failure. The earlier that kidney disease is found, the greater the chance of slowing or stopping it from getting worse.
Symptoms of an eGFR value that is too low
The symptoms of an eGFR value that is too low are not always immediately noticeable. During mild stages when the value is only slightly lowered, there are sometimes no symptoms at all. When low eGFR ha progressed to moderate or severe renal failure, the following symptoms may occur:
- Itchiness
- Nausea
- Feeling unwell
- Fluid retention
- Swollen ankles
- Urinating either too much or too little
- Shortness of breath
- Bone weakness
- High blood pressure
- Feeling cold
- Fatigue
eGFR Testing
Testing your eGFR with Homed-IQ provides insight into the filtration rate of the kidneys. This biomarker is part of the Liver and Kidney Function Test. This home test consists of a urine test and a finger prick for blood collection, after which a certified laboratory carries out the analysis. In addition to the eGFR value, this test provides insight into a number of other biomarkers, such as ALT, AST, GammaGT, Bilirubin, Albumin, Creatinine, eGFR, and Alkaline Phosphatase. With this, the test offers several parameters to determine your kidney and liver function. In the initial stages of kidney or liver disease, symptoms are not always noticeable. Therefore, testing can offer early detection.
How can I increase my eGFR?
eGFR can be increased by following a specific diet. It is important to avoid salt as much as possible and to limit protein intake (UMCG). Depending on the level of the kidney function, it may also be necessary to take medication. For example, medicines that lower blood pressure or a vitamin D supplement. If eGFR is severely low, medication to support the filtration function of the kidneys in the removal of waste may also be prescribed. More severe kidney failure may require dialysis or a kidney transplant.
- Diet can help improve eGFR: it is important to reduce salt intake; protein consumption should be limited.
- Medication may be needed to support kidney function: blood pressure-lowering drugs or vitamin D supplements may be prescribed.
- Severely low eGFR may require medication to support filtration; advanced kidney failure may require dialysis or a transplant.
Summary
eGFR is a key marker of kidney function, calculated using creatinine levels, age, and other factors. A value above 90 mL/min/1.73 m² is generally considered normal, while lower values may indicate decreased kidney performance. Causes of low eGFR include age, chronic kidney disease, diabetes, high blood pressure, and certain medications. Although early stages may show no symptoms, advanced kidney damage can lead to fatigue, fluid retention, and bone weakness. eGFR can be supported through a kidney-friendly diet, medication, and—if necessary—dialysis or transplant. With Homed-IQ’s at-home test, tracking your kidney health is simple, accessible, and informative.
