Adjusting Calcium for Albumin
Corrected Calcium Formula
Corrected calcium = Measured calcium + 0.02 × (40 − albumin). Low albumin lowers total calcium without affecting ionised (biologically active) calcium — adjusted calcium corrects for this. Ionised calcium measurement avoids this confusion.
Causes of Hypercalcaemia (High Calcium)
| Cause | % of Cases | Clue |
|---|---|---|
| Primary hyperparathyroidism | 50% | High PTH with high Ca²⁺ |
| Malignancy | 25–30% | Low PTH; weight loss, anaemia |
| Vitamin D toxicity | <5% | History of high-dose supplementation |
| Sarcoidosis | Uncommon | Lung involvement, raised ACE |
| Thiazide diuretics | Drug cause | Recent drug history |
| Milk-alkali syndrome | Uncommon | Excessive calcium supplement use |
Symptoms of Hypercalcaemia
- Remembered as 'Bones, Stones, Groans, Moans, Psychic Overtones'
- Bones: bone pain, fractures
- Stones: renal calculi (kidney stones)
- Groans: constipation, nausea, vomiting
- Moans: muscle weakness, fatigue
- Psychic: confusion, depression, lethargy
PTH Is Always the Next TestAlways check PTH alongside calcium. High PTH with high calcium = primary hyperparathyroidism. Low/suppressed PTH with high calcium = malignancy or vitamin D excess until proven otherwise.
What is hypercalcaemia of malignancy?
Cancer can raise calcium via PTHrP (parathyroid-hormone-related protein), bone metastases, or ectopic vitamin D production. It's a sign of advanced disease and requires urgent management.
What causes low calcium (hypocalcaemia)?
Vitamin D deficiency, hypoparathyroidism (post-thyroid surgery), magnesium deficiency (blocks PTH), acute pancreatitis, renal failure, and malabsorption syndromes.
What are symptoms of low calcium?
Tingling in fingers/lips, muscle cramps (tetany), Trousseau's sign (carpal spasm with BP cuff), Chvostek's sign (facial twitch with tap), and in severe cases, seizures and laryngospasm.
How is hypercalcaemia treated?
IV fluids (rehydration) is the first step. Bisphosphonates (zoledronic acid) for malignancy-related hypercalcaemia. Treat the underlying cause. Steroids work for sarcoidosis and vitamin D toxicity.
Medical Disclaimer: This page is for general education only and does not replace professional medical advice. Always consult a qualified healthcare provider.