Hypocalcaemia

Key Points
- Mild Hypocalcaemia (1.9mmol/L – 2.2mmol/L):
- Initiate Oral Calcium Supplementation –> e.g. Sandocal 1000: 2 tablets BD; Adcal: 3 tablets BD; Cacit: 4 tablets BD; Calcichew Forte: 2 tablets BD
- Replace vitamin D and magnesium as needed – discontinue any precipitating medications:
- Give IV Magnesium if level <0.5mmol/L:
- Infuse 24 mmol/24h (e.g., 6g MgSO₄ in 500 mL Normal Saline or 5% Dextrose) – otherwise oral replacement is suitable
- Monitor serum magnesium and aim for normal levels
- Other causes –> identify and treat underlying condition:
- Post-thyroidectomy patient will require monitoring – seek specialist advice before discharging patient
- Initiate Oral Calcium Supplementation –> e.g. Sandocal 1000: 2 tablets BD; Adcal: 3 tablets BD; Cacit: 4 tablets BD; Calcichew Forte: 2 tablets BD
- Severe Hypocalcaemia (<1.9mmol/L):
- Immediate IV Calcium Gluconate Administration:
- Bolus Dose:
- 10–20 mL of 10% calcium gluconate in 50–100 mL of 5% dextrose
- Administer IV over 10 minutes with ECG monitoring
- Repeat until the patient is asymptomatic
- Follow-Up Infusion:
- 100 mL of 10% calcium gluconate (10 vials) diluted in 1L Normal Saline or 5% Dextrose
- Infuse at 50–100 mL/h, titrated to achieve normocalcaemia
- Calcium chloride can be used but is more irritant (use only via central line)
- Bolus Dose:
- Treat underlying cause:
- Post-operative hypocalcaemia / hypoparathyroidism will require monitoring +/- active vitamin D (e.g. alfacalcidol) – seek specialist advice before initiating any further treatment
- Correct Vitamin D Deficiency & Hypomagnesaemia
- Risks of IV Calcium Administration:
- Uncommon but possible complications:
- Local: Thrombophlebitis
- Systemic: Cardiotoxicity, hypotension, flushing, nausea, vomiting, sweating
- Patients at high risk (i.e. patient with cardiac arrhythmias or on digoxin):
- Require continuous ECG monitoring during IV calcium replacement
- Uncommon but possible complications:
- Immediate IV Calcium Gluconate Administration:
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
Cause | Examples/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 |
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
Test | Reason |
---|---|
Serum calcium (adjusted for albumin) | Confirm hypocalcaemia; note severity level (<1.9 mmol/L often symptomatic). |
Phosphate | Elevated phosphate can accompany hypoparathyroidism. |
Parathyroid hormone (PTH) | Distinguishes between hypoparathyroidism (low/absent PTH) and other causes. |
Urea and electrolytes | Check renal function and associated electrolyte abnormalities. |
Magnesium | Hypomagnesaemia can cause or exacerbate hypocalcaemia. |
Vitamin D | Identifies deficiency and guides supplementation. |
6. Immediate Management
Defining Mild vs Severe Hypocalcaemia
Severity | Serum Calcium | Clinical 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) |
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).
- If post-thyroidectomy and patient is asymptomatic, recheck serum calcium in 24 h.
- 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.
- Follow bolus with a continuous infusion:
- 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).
- Treat the underlying cause:
- 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
- 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
- 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