What is a Renal (Kidney) Ultrasound?
What is a renal (kidney) ultrasound? An ultrasound scan uses ultrasound, or high-frequency sound waves, to create an image (picture) of part of the inside of your body, such as your kidney. It is used...

Chronic Kidney Disease (CKD) can be a scary diagnosis, but the truth is that for many people, it is a manageable condition rather than an immediate emergency.
If you’ve been looking at your blood test results and wondering, “When should I worry about CKD?”, this guide breaks down the stages, symptoms, and the clinical “red flags” that doctors look for.
As kidneys become damaged, they struggle to filter creatinine (a waste product) out of your blood.
To understand when to worry, you first need to understand eGFR (Estimated Glomerular Filtration Rate). This is calculated by putting the blood creatinine level into an equation. Think of GFR as the “percentage” of kidney function you have left.
The medical community divides CKD into five stages. While Stage 4 is typically the point of significant clinical concern, your individual situation depends on how fast the numbers are changing.
eGFR: 60–120 mL/min
What it means: You have evidence of kidney damage (like protein in the urine) or a structural issue, but your kidneys are still filtering waste effectively.
Symptoms: None.
Should you worry? Generally, no. Focus on managing “insult factors” like high blood pressure or diabetes to keep your kidneys healthy.
eGFR: 30–59 mL/min
What it means: 3A is early mild loss; 3B is later mild-to-moderate loss.
Symptoms: Usually none, though some experience mild fatigue or fluid retention in 3B.
Should you worry? This is the “action stage.” Doctors will focus on slowing progression. If you hit Stage 3B, your GP should consult with a nephrologist (kidney specialist).
eGFR: 15–29 mL/min
What it means: Your kidneys are significantly impaired.
Symptoms: Moderate symptoms start appearing—swollen ankles, fatigue, and changes in urination frequency.
Should you worry? Yes. This is the stage where you must be under the direct care of a nephrologist. This is also when doctors begin discussing future options like dialysis or a kidney transplant.
eGFR: Below 15 mL/min
What it means: Your kidneys are close to or at failure.
Symptoms: Severe—nausea, itching, shortness of breath, and significant swelling.
Should you worry? Yes, very much. This is a critical stage requiring life-sustaining treatment, such as dialysis, a transplant, or supportive care (not having dialysis).
A single eGFR result is just a snapshot. Doctors are much more interested in the trend over time. This is where the “worry” becomes relative.
The “Stable” vs. “Progressive” Rule
CKD does not always get worse. Many people stay at Stage 3 for their entire lives.
Stable CKD: If your eGFR stays at 40 for five years, it is often not a major concern.
Progressive CKD: If your eGFR drops from 80 to 40 in six months, that is a medical red flag, regardless of the stage.
The Age Factor
Kidney function naturally declines as we get older.
An 89-year-old with an eGFR of 25 (Stage 4) might never need dialysis; they are likely to “die with the problem, not of it.”
A 29-year-old with an eGFR of 55 (Stage 3A) is a high-priority patient because they have decades of life ahead and need their kidneys to last.
While Stage 4 is the formal threshold for high concern, you should seek a specialist’s opinion if:
Red Flag Symptoms (Seek Urgent Medical Attention)
Note. Any of these symptoms could mean CKD4 is worsening, or you have reached CKD5 (kidney failure), or Acute Kidney Injury (AKI) on top of CKD.
Red Flag Investigations (Seek Medical Attention Soon)
Bottom Line: Don’t panic over one blood test. Look at the trend, manage your blood pressure, and keep your follow-up appointments. However ..
Note 1. A blood potassium of 6.0 mmol/L or over needs to be addressed today. If its over 6.5 mmol/L it is a medical emergency. Go to A&E today.
Note 2. If the blood urea is over 50 mmmol/L, you need to be considered for dialysis today.
Are you currently tracking your eGFR results, or are you looking for advice on how to interpret a recent test?
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