Hypocalcaemia DDx

Causes of HYPOcalcaemia

Commonest causes: HYPOalbuminaemia and HYPERventilation

  1. Factitious (commonest)
    • Low albumin
  2. Metabolic (transcellular as for potassium)
    • Primary respiratory alkalosis (HYPERventilation)
    • Chronic alkalosis
  3. Endocrine (Decreased Ca uptake, increased excretion)
    • Reduced PTH (associated raised PO4 as cannot excrete)
      • Hypoparathyroidism (raised PO4)
      • Pseudohypoparathyroidism (raised PO4)
      • Thyroid or parathyroid surgery
    • Increased calcitonin (decreased Ca and PO4)
      • Medullary thyroid carcinoma
    • Decreased Vitamin D (decreased GIT calcium absorption (small))
  4. Increased PHOSPHATE(precipitates calcium in serum)
    • Tumour lysis syndrome (↑K+ ,↑PO4, ↓Ca++)
    • Rhabdomyolysis
    • Chronic renal failure
  5. Excessive CITRATE in circulation (precipitates calcium)
    • Whole blood transfusion
    • Plasmapheresis
  6. Increased bone formation and turnover (Osteoblastic activity)
    • Malignancy (Breast, lung, thyroid, kidney, prostate)
    • Osteomalacia (Increased alkaline phosphatase)
  7. Other
    • Sepsis and Toxic shock syndrome
    • Pancreatitis (PO4 normal)
    • Overhydration
  8. Drugs
    • B blocker OD, phenytoin, gentamicin, heparin
    • Cimetidine, Ca channel blocker


Calcium is excitable membrane stabiliser. Neuromuscular excitability and irritability is predominant

  • Neurological
    • Hyperreflexia and seizures
    • Paraesthesia of extremities and face (Digital and peri-oral)
    • Confusion, hallucinations, dementia
  • Muscular
    • Laryngospasm, stridor, tetany
    • Muscle spasm, cramps and tetany
      • Chvostek sign (Facial nerve tap….twitch corner of mouth)
      • Trousseau sign (BP cuff on arm for 3mins induces carpopedal spasm)
  • Cardiac
    • Decreased myocardial contractility and heart failure


  • Arrhythmia
  • ECG changes
  • QTc prolongation (With low K+, Mg2+, Ca2+)
  • T wave inversion
  • Complete heart block
  • Torsades des Pointes


  • Assess and treat underlying cause
  • Correct acidosis and hypomagnesaemia
  • Replace Calcium


  • Oral Calcium supplements and Vitamin D rich milk


  • Parenteral Calcium
    • Calcium chloride (10ml 10% 13.6mEq)
    • Calcium gluconate (10ml 10% 4.6mEq)

CCC Differential Diagnosis Series


Anosmia, Ataxia, Blepharospasm, Bulbar and Pseudobulbar palsy, Central Pontine Myelinosis, Cerebellar Disease, Chorea, Cranial nerve lesions, Dementia, Dystonia, Exophthalmos, Eye trauma, Facial twitches, Fixed dilated pupil, Horner syndrome, Loss of vision, Meningism, Movement disorders, Optic disc abnormality, Parkinsonism, Peripheral neuropathy, Radiculopathy, Red eye, Retinal Haemorrhage, Seizures, Sudden severe headache, Tremor, Tunnel vision


Bronchial breath sounds, Bronchiectasis, High airway pressures, Massive haemoptysis, Sore throat, Tracheal displacement


Atrial Fibrillation, Bradycardia, Cardiac Failure, Chest Pain, Murmurs, Post-resuscitation syndrome, Pulseless Electrical Activity (PEA), Pulsus Paradoxus, Shock, Supraventricular tachycardia (SVT), Tachycardia, VT and VF, SVC Obstruction


Abdominal distension, Abdominal mass, Abdominal pain, Asterixis, Dysphagia, Hepatomegaly, Hepatosplenomegaly, Large bowel obstruction, Liver palpation abnormalities, Lower GI haemorrhage, Malabsorption, Medical causes of abdominal pain, Rectal mass, Small bowel obstruction, Upper GI Haemorrhage


Genital ulcers, Groin lump, Scrotal mass, Urine colour, Urine Odour, Urine transparency


Arthritis, Shoulder pain, Wasting of the small muscles of the hand


Palmar erythema, Serious skin signs in sick patients, Thickened Tethered Skin, Leg ulcers, Skin Tumour, Acanthosis Nigricans


Diabetes Insipidus, Diffuse Goitre, Gynaecomastia, Hirsutism, Hypoglycaemia, SIADH, Weight Loss




Floppy infant 


Anaphylaxis, Autoimmune associated diseases, Clubbing, Parotid Swelling, Splinter haemorrhages, Toxic agents and abnormal vitals, Toxicological causes of cardiac arrest


CHEST: Atelectasis, Hilar adenopathy, Hilar enlargement on CXR, Honeycomb lung, Increased interstitial markings, Mediastinal widening on mobile CXR, Pulmonary fibrosis, Pseudoinfiltrates on CXR, Pulmonary opacities on CXR,
Gas on abdominal X-ray, Kidney mass,
Intracranial calcification, Intracranial structures with contrastVentriculomegaly,
OTHER: Pseudofracture on X-Ray


LOW: Anaemia, Hypocalcaemia, hypochloraemia, Hypomagnesaemia

HIGH: Bilirubin and Jaundice, HyperammonaemiaHypercalcaemia, Hyperchloraemia, Hyperkalaemia, Hypermagnesaemia

ACID BASE: Acid base disorders, Resp. acidosis, Resp. alkalosis,

Creatinine, CRP, Dipstick Urinalysis, Laboratory Urinalysis, Liver function tests (LFTs), Pleural fluid analysis, Urea, Urea Creatinine Ratio, Uric acid, Urinalysis, Urine Electrolytes


CCC 700 6

Critical Care


BA MA (Oxon) MBChB (Edin) FACEM FFSEM. Emergency physician, Sir Charles Gairdner Hospital.  Passion for rugby; medical history; medical education; and asynchronous learning #FOAMed evangelist. Co-founder and CTO of Life in the Fast lane | Eponyms | Books | Twitter |

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