Hypocalcaemia

1. Epidemiology
  • Acute hypocalcaemia can be life-threatening.
  • The most common cause of acute symptomatic hypocalcaemia in hospital practice is disruption of parathyroid gland function following total thyroidectomy (hypoparathyroidism may be temporary or permanent).
2. Aetiology
CauseExamples/Details
Surgical Disruption of the Parathyroid Glands– Post-thyroidectomy (most common in hospital practice)
– Following selective parathyroidectomy
Hypoparathyroidism– Autoimmune 
– Congenital 
– Haemochromatosis 
– Low Magnesium (↓Mg²⁺)
Vitamin D-Related– Severe vitamin D deficiency
– Insufficient synthesis (e.g. chronic kidney disease)
Magnesium Deficiency– Consider PPI-associated hypomagnesaemia
Chelation or Depletion– High phosphate (tumour lysis syndrome, pancreatitis)
– Citrate in blood transfusions
Drug-Induced– Cytotoxic drugs
– Phenytoin
– Large-volume blood transfusions (citrate)
Others– Rhabdomyolysis
Causes of Hypocalcaemia

3. Risk Factors
  • Recent neck surgery (especially total thyroidectomy or parathyroidectomy).
  • Underlying hypoparathyroidism of any cause.
  • Severe vitamin D deficiency.
  • Proton pump inhibitor use (risk of hypomagnesaemia).
  • Chronic kidney disease (impairment of vitamin D activation).
  • Certain medications (e.g. cytotoxic agents, phenytoin).
4. Symptoms
General Clinical Features
  • Mild hypocalcaemia may present with:
    • Cramps
    • Perioral numbness/paraesthesiae
  • Severe or more pronounced hypocalcaemia may present with:
    • Tetany and carpopedal spasm (Trousseau’s sign)
    • Facial muscle twitching (Chvostek’s sign)
    • Laryngospasm
    • Seizures
    • Prolonged QT interval on ECG
    • Arrhythmias
Additional Mnemonic (SPASMODIC)
  • Spasms (carpopedal spasms = Trousseau’s sign)
  • Perioral paraesthesiae
  • Anxious, irritable, irrational
  • Seizures
  • Muscle tone increased in smooth muscle (colic, wheeze, dysphagia)
  • Orientation impaired (confusion)
  • Dermatitis
  • Impetigo herpetiformis (rare in pregnancy)
  • Chvostek’s sign, choreoathetosis, cataract, cardiomyopathy (long QT)
5. Diagnosis

History and Examination

  • Elicit any history of recent neck surgery (thyroidectomy, parathyroidectomy).
  • Assess for symptoms typical of hypocalcaemia (e.g. paraesthesiae, tetany).
  • Evaluate for possible vitamin D deficiency (diet, sunlight exposure) or magnesium-lowering medications (e.g. PPIs).

Investigations

TestReason
Serum calcium (adjusted for albumin)Confirm hypocalcaemia; note severity level (<1.9 mmol/L often symptomatic).
PhosphateElevated phosphate can accompany hypoparathyroidism.
Parathyroid hormone (PTH)Distinguishes between hypoparathyroidism (low/absent PTH) and other causes.
Urea and electrolytesCheck renal function and associated electrolyte abnormalities.
MagnesiumHypomagnesaemia can cause or exacerbate hypocalcaemia.
Vitamin DIdentifies deficiency and guides supplementation.
Key Laboratpry Investigations in Hypocalcaemia

6. Immediate Management
Defining Mild vs Severe Hypocalcaemia
SeveritySerum CalciumClinical Presentation
Mild>1.9 mmol/L (asymptomatic)Minimal or no symptoms
Severe<1.9 mmol/L (or symptomatic at any level)Potentially life-threatening symptoms (tetany, seizures, arrhythmias)
Hypocalcaemia Severity Levels

Mild Hypocalcaemia
  • Oral Calcium Supplementation
    • Sandocal 1000, 2 tablets twice daily (BD)
    • Alternatives:
      • Adcal 3 tablets BD
      • Cacit 4 tablets BD
      • Calcichew Forte 2 tablets BD
  • Monitoring and Adjustment
    • If post-thyroidectomy and patient is asymptomatic, recheck serum calcium in 24 h.
      • If adjusted calcium >2.1 mmol/L, patient can be discharged with follow-up in 1 week.
      • If serum calcium remains between 1.9 and 2.1 mmol/L, increase Sandocal 1000 to 3 tablets BD.
      • If still hypocalcaemic beyond 72 h post-operatively despite oral calcium, start alfacalcidol 0.25 micrograms/day (or calcitriol).
  • Vitamin D Deficiency
    • Load with approximately 300,000 units of colecalciferol or ergocalciferol over 6–10 weeks if this is the identified cause.
  • Hypomagnesaemia
    • Stop any precipitating medication (e.g. PPIs if possible).
    • Give intravenous Mg²⁺ replacement (e.g. 24 mmol/24 h, typically 6 g MgSO₄ in 500 mL Normal saline or 5% dextrose).
    • Aim for normal serum magnesium levels.
  • Address Other Underlying Conditions
    • Treat pancreatitis, rhabdomyolysis, or other causes as appropriate.

Severe Hypocalcaemia
  • Overview
    • Serum calcium <1.9 mmol/L and/or symptomatic → Medical emergency.
    • Administer intravenous (IV) calcium gluconate with ECG monitoring.
  • Initial Bolus
    • 10–20 mL of 10% calcium gluconate in 50–100 mL of 5% dextrose over 10 minutes.
    • Repeat until patient is asymptomatic (monitor ECG throughout).
  • Calcium Infusion
    • Follow bolus with a continuous infusion:
      • Dilute 100 mL of 10% calcium gluconate (10 vials) in 1 L Normal saline or 5% dextrose.
      • Infuse at 50–100 mL/h, titrating to achieve normocalcaemia.
  • Further Steps
    • Treat the underlying cause:
      • In post-operative hypoparathyroidism, commence alfacalcidol or calcitriol (0.25–0.5 micrograms daily).
      • Address vitamin D deficiency or hypomagnesaemia if present.
    • Note: Large-volume calcium infusions are not suitable for patients with end-stage renal failure or on dialysis (refer to NKF KDOQI guidelines for renal-specific management).
  • Potential Hazards of IV Calcium
    • Local thrombophlebitis
    • Cardiotoxicity, hypotension
    • ‘Calcium taste’, flushing, nausea, vomiting, sweating
    • Continuous ECG monitoring needed in patients with arrhythmias or on digoxin therapy
7. Long-term Management

7.1 Addressing Underlying Causes

  • Definitive management of primary hyperparathyroidism may involve parathyroidectomy, especially in severe cases or those resistant to medical therapy
  • Malignancy-related hypercalcaemia may require ongoing oncology treatments (e.g. chemotherapy) and additional agents (e.g. calcimimetics)

7.2 Ongoing Monitoring

  • 1-alpha Hydroxylated Vitamin D Metabolites (e.g. Alfacalcidol, Calcitriol):
    • Start at approximately 0.25–0.5 micrograms daily (oral or IV if absorption is in question).
    • Monitor frequently for hypercalcaemia during stabilisation.
  • Monitoring Schedule
    • Check adjusted serum calcium about one week post-discharge.
    • If stable, recheck at 1, 3, and 6 months.
    • Further monitoring intervals depend on clinical stability.
  • Specialist Follow-Up:
    • Long-term follow-up by a specialist experienced in calcium disorders is recommended.

Written by Dr Ahmed Kazie MD, MSc
  • References
    1. Turner J, Gittoes N, Selby P, _ _. SOCIETY FOR ENDOCRINOLOGY ENDOCRINE EMERGENCY GUIDANCE: Emergency management of acute hypocalcaemia in adult patients. Endocrine Connections [Internet]. 2016 Sep [cited 2025 Feb 3];5(5):G7–8. Available from: https://ec.bioscientifica.com/view/journals/ec/5/5/G7.xml?body=fullhtml-62407
    2. Wilkinson I, Raine T, Wiles K, Hateley P, Kelly D, McGurgan I. OXFORD HANDBOOK OF CLINICAL MEDICINE International Edition. 11th ed. Oxford University Press; 2024.

Last Updated: February 2025