Why the kidneys are checked
The kidneys filter the blood, remove waste and regulate fluids, salts and blood pressure. Chronic kidney disease can progress for years without any symptoms — by the time complaints appear, the damage is often already advanced. Early detection with simple tests allows treatment that slows it down.
Who should be checked
- people with diabetes
- people with hypertension
- people with cardiovascular disease
- a family history of kidney disease
- long-term use of certain medicines (e.g. anti-inflammatory drugs)
The frequency of checks is set individually — for most patients with diabetes or hypertension, once a year.
The two main tests
1. Creatinine and eGFR
Creatinine is measured in the blood and from it the estimated glomerular filtration rate (eGFR) is calculated — how well the kidneys filter.
- eGFR is influenced by age, muscle mass and clinical condition.
- In selected cases, measuring cystatin C makes the assessment more accurate.
2. Urine albumin/creatinine ratio (ACR)
It measures the loss of albumin in the urine — an early sign of kidney damage, even when eGFR is normal.
- The most suitable sample is the first-morning urine.
- Fever, intense physical activity, urinary infection and menstruation can raise it temporarily — which is why a raised value is usually repeated.
eGFR and ACR together determine the stage of the disease and the risk.
Diagnosis takes time
A single abnormal result does not automatically mean chronic kidney disease. The diagnosis is made when the damage or reduced function lasts at least 3 months. If acute injury is suspected, assessment is done immediately.
Other tests
- Urinalysis — may show blood, protein or signs of infection.
- Urine culture — only when infection is suspected; it does not assess kidney function.
- Potassium, sodium and other electrolytes, urea, blood count — and, in advanced stages, calcium, phosphorus and PTH.
- Urea is influenced by hydration and diet, so it is not interpreted on its own.
- 24-hour urine — only for special indications.
- Kidney ultrasound — for size, structure, stones or obstruction.
How to protect your kidneys
- keep blood pressure and diabetes well controlled
- do not take anti-inflammatory drugs (ibuprofen, diclofenac etc.) for long periods without advice
- do not change medicine doses on your own — many medicines are adjusted according to eGFR
- avoid products that promise “kidney cleansing”
- drink fluids as needed, except when your doctor has restricted them
Key sources
This information is educational and does not replace a visit to the doctor. Do not change your treatment without consulting your doctor. Updated: October 2026.