Kidney blood tests – what’s normal and abnormal?
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Kidney doctors love blood tests. Full stop.
Why? It is because it is impossible for them to judge the function of the kidneys solely by asking you questions (doctors call this the ‘history’) and physical examination. So, what is normal and abnormal? Here goes.
So. Kidney blood tests – what’s normal?
Two normal functioning kidneys will maintain the following tests and symptoms in the normal range. The kidney function that is reflected by the test or symptom is given in brackets.
- Normal creatinine = 60-120 mcmol/L (waste removal)
- Normal eGFR = 90-120 mls/min (45-60 mls/min for a single kidney). This number is derived from the creatinine, and goes down as creatinine goes up in CKD (waste removal)
- Normal urea = 3-7 mmol/L (waste removal)
- Normal sodium (Na) = 135-145 mmol/L (salts removal)
- Normal potassium (K) = 3.5-5.3 mmol/L (salts removal)
- Normal glucose = 4-6 mmol/L (diabetes). May be raised if patient has diabetes
- Normal bicarbonate = 22-28 mmol/L (acid removal)
- Normal calcium = 2.2-2.6 mmol/L (bone health)
- Normal phosphate = 0.8-1.4 mmol/L (bone health)
- Normal PTH <5 pcmol/L (bone health)
- Normal haemoglobin (‘Hb’) = 110-150 g/L in a woman, 130-170 g/L in a man (red cell production)
- Normal blood pressure = 130/80 mmHg or less – though not a blood test, this is a key sign of kidney health.
Kidney blood tests – what’s abnormal (i.e. in CKD)?
- Increased creatinine >120 mcmol/L (waste removal)
- Decreased GFR <60 mls/min (< 30 mls/min for a single kidney).
- Increased urea >7 mmol/L (waste removal)
- Normal sodium (Na) = 135-145 mmol/L (salts removal)
- Increased potassium (K) >5.3 mmol/L (can be normal or low) (salts removal)
- Normal glucose = 4-5 mmol/L (diabetes)
- Decreased bicarbonate <22 mmol/L (acid removal)
- Decreased calcium <2.2 mmol/L (bone health)
- Increased >1.4 mmol/L (bone health)
- Increased PTH >5 pcmol/L (bone health)
- Decreased haemoglobin (‘Hb’) <110 g/L in a woman, <130 in a man (red cell production). This is called anaemia
- Increased blood pressure >140/90 mmHg.
Note. Even though this is the typical pattern for CKD, 1. most tests only start to become abnormal when the patient gets to CKD4 (creatinine > 200 mcmol/L), and, 2. patients vary a lot and may not have abnormal results in them all. For example, they may have no anaemia.
Summary
We have described kidney blood tests – what’s normal and abnormal. We hope it has been helpful.
Last Reviewed on 5 April 2024