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Andy Stein

A normal blood calcium level

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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
  • Hyperphosphataemia – 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.

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