What is a normal blood calcium level?
Normal blood calcium level
Normal adjusted calcium level is 2.2.-2.6 mmol/L.
Note. Normal ionised calcium level is 1.2.-1.3 mmol/L. This is the level reported in an arterial blood gad (ABG).
Low calcium level (hypocalcaemia)
Hypocalcaemia is defined as an adjusted calcium level of <2.2 mmol/L.
Causes include:
- Hypoparathyroidism
- Vitamin D deficiency
- Hyperphosphatemia – phosphate binds to calcium to form calcium phosphate, reducing free calcium
- Chronic kidney disease (CKD) – reduced calcitriol synthesis
- Acute pancreatitis – free fatty acids bind calcium, reducing levels of free calcium.
- Respiratory alkalosis – in alkalosis, calcium ions associate with albumin with greater affinity, thus reducing free and active calcium.
High calcium level (hypercalcaemia)
Hypercalcaemia is defined as an adjusted calcium level of >2.6 mmol/L.
Causes include:
- Hyperparathyroidism
- Myeloma
- Malignant tumour – some tumours secrete parathyroid-hormone-related peptide (PTHrP). This mimics PTH, leading to hypercalcaemia
- Vitamin D intoxication – excess vitamin D causing increased intestinal absorption of calcium
- Thiazide diuretics – increase renal reabsorption of calcium causing excess calcium in the blood
- Other – Milk-alkali syndrome (excess calcium consumption, usually due to calcium carbonate), Paget’s disease, sarcoidosis.
