The Killer Hidden in the Admission Bloods: A Guide to Hypercalcaemia

That bleep from your on-call phone in the middle of the night can be daunting. You’re asked to see a patient with new-onset confusion, and the list of potential causes feels a mile long. It's a classic challenge for any resident doctor, but in patients with a known cancer diagnosis, there’s a metabolic emergency you must keep in mind: severe hypercalcaemia.

Let’s walk through a typical case and break down exactly what you need to know to manage this life-threatening condition confidently.

The Case: Presentation to A&E

A 75-year-old woman is brought into Accident & Emergency by ambulance. Her GP has sent her in with a letter flagging altered consciousness.

Until recently, she was living independently. However, her family reports that over the last five days, she has become progressively unwell with vague abdominal pain, a poor appetite, and increasing drowsiness. On the day of admission, they struggled to wake her up. When you assess her, she responds to painful stimuli and intermittently follows simple commands. Her GCS is 12.

Her past medical history includes:

• Multiple myeloma

• Hypertension

• Type 2 diabetes

• Hypercholesterolaemia

She is receiving palliative care for bone pain and takes regular oral morphine, with no recent change in dose.

Her vital signs are stable. Her pupils are equal and reactive, and a neurological examination reveals no focal deficits. The on-call registrar starts the standard investigations for altered consciousness. An initial set of bloods and a CT head come back with no clear cause.

Given her active cancer, should you be considering anything specific?

The answer arrives with the blood gas analysis: the ionised calcium is critically high. A follow-up lab test confirms a corrected calcium level of 3.9 mmol/L. This is severe, life-threatening hypercalcaemia.

Oncological Vigilance: The Differential Diagnosis

While patients with cancer can become confused for all the usual reasons (infection, dehydration, etc.), you need to maintain a high index of suspicion—what we call oncological vigilance—for emergencies specific to their condition.

For a patient with cancer and altered consciousness, your differential should always include:

• Hypercalcaemia of Malignancy (HCM): The most common metabolic emergency in oncology.

• CNS Metastases: Space-occupying lesions in the brain.

• Acute Kidney Injury (AKI): May be due to various causes, including cast nephropathy in myeloma.

• Opioid Toxicity: Opioid metabolites can accumulate rapidly if a patient develops AKI.

• Hyperviscosity Syndrome: Particularly in conditions like myeloma or Waldenström's macroglobulinaemia.

The good news is that you don’t need specialist tests to begin your assessment. A solid foundation includes a thorough medication history, a CT head scan, and routine bloods—including a corrected calcium, a full blood count, and urea & electrolytes (U&Es)—which will point you in the right direction.

What is Hypercalcaemia of Malignancy?

Hypercalcaemia is the most common metabolic emergency seen in oncology, affecting an estimated 20–30% of patients with cancer at some point during their illness. It's most frequently associated with:

• Multiple myeloma

• Breast cancer

• Lung cancer (especially squamous cell carcinoma)

• Renal cell carcinoma

Signs and Symptoms: Stones, Bones, Groans, and Moans

The clinical presentation of hypercalcaemia depends not just on the absolute calcium level, but also on how quickly it has risen. The normal range for adjusted total calcium is typically 2.20–2.60 mmol/L.

A crucial clinical pearl: Calcium is bound to albumin in the blood. Many patients with cancer are malnourished and have low albumin levels (hypoalbuminaemia). This means a laboratory result for total calcium may appear falsely low. You must always calculate the corrected calcium.

The standard UK formula is:
Corrected Calcium (mmol/L) = Total Calcium (mmol/L) + 0.02 x [40 - patient’s albumin (g/L)]

Symptoms of an acute hypercalcaemic crisis, often seen with levels above 3.5 mmol/L, can be remembered using the classic mnemonic:

• Stones: Renal colic, polyuria (leading to dehydration), and nephrolithiasis.

• Bones: Bone pain and pathological fractures.

• Groans: Nausea, vomiting, constipation, and abdominal pain (which can even mimic an acute abdomen or pancreatitis).

• Moans: Poor concentration, confusion, lethargy, and coma.

Hypercalcaemia: ECG Changes

Severe hypercalcaemia is cardiotoxic and can produce distinct ECG findings. It is commonly tested in exams and a vital abnormality to spot on the wards.

The hallmark change is a shortened QT interval (<350 ms).

In more severe cases, you may also see:

• PR interval prolongation

• QRS complex widening

• Osborne waves (J waves)

• ST-segment elevation

• Ultimately, bradyarrhythmias, AV block, and cardiac arrest.

The ECG from our patient showed a prominent Osborne wave in lead II and ST elevation in lead III, confirming the severity of her condition.

Hypercalcaemia Management: An Emergency Algorithm

You've identified severe hypercalcaemia (>3.5 mmol/L) with neurological symptoms. This is a medical emergency requiring immediate action. Follow these steps, guided by NICE and Royal College guidelines.

• Aggressive IV Fluid Resuscitation
  This is the single most important first step. Patients with HCM are almost always significantly dehydrated due to vomiting and calcium-induced nephrogenic diabetes insipidus (polyuria).

  • Action: Start with 0.9% sodium chloride. Give a 500-1000 mL bolus in the first hour, then continue with an infusion of 200-300 mL/h.

  • Goal: Aim for a urine output of 100–150 mL/h. Rehydration alone can significantly lower the calcium level.

• Loop Diuretics (e.g., Furosemide)
  This used to be a routine step, but guidelines have changed.

  • Action: DO NOT give furosemide until the patient is euvolaemic (i.e., fully rehydrated). Giving it to a dehydrated patient will worsen AKI. Once fluid status is restored, IV furosemide (e.g., 20–40 mg) can help promote calcium excretion.

• Bisphosphonates (The Definitive Treatment)
  These are the cornerstone of HCM management. They work by inhibiting osteoclast activity.

  • Action: Zoledronic acid 4 mg given as a slow IV infusion (over at least 15 minutes) is the standard choice.

  • Caveat: Bisphosphonates are effective but have a delayed onset of action (2–4 days). They are also nephrotoxic, so you must check the patient's renal function first. The dose may need to be reduced or withheld in severe AKI.

• Calcitonin
  Calcitonin acts quickly (within 4-6 hours) but its effect is short-lived. It's often used as a bridge until bisphosphonates take effect.

  • Action: The dose is 4–8 IU/kg, given subcutaneously or intramuscularly every 6–12 hours. However, availability varies between hospital trusts.

• Corticosteroids
  Steroids are particularly effective in haematological malignancies (like myeloma and lymphoma) or in hypercalcaemia driven by excess 1,25-dihydroxyvitamin D.

  • Action: Use hydrocortisone 100 mg IV every 6 hours or prednisolone 40–60 mg orally daily. They work by reducing intestinal calcium absorption and have a cytotoxic effect on the malignant cells.

• Denosumab
  This monoclonal antibody (a RANKL inhibitor) is a great alternative to bisphosphonates, especially in patients with severe renal impairment where zoledronic acid is contraindicated.

  • Action: A single 120 mg dose is given subcutaneously.

• Haemodialysis
  This is a last resort for the most severe and refractory cases.

  • Indications:

    • Severe renal failure with oliguria or anuria.

    • Failure of pharmacological treatment.

    • Life-threatening symptoms like severe arrhythmias or coma.

Key Takeaways for Your Next On-Call Shift

• Think Calcium: In any patient with cancer presenting with confusion, drowsiness, or delirium, corrected calcium must be included in your initial bloods.

• Emergency Threshold: A corrected calcium level >3.5 mmol/L is a medical emergency.

• Fluids First: Aggressive rehydration with 0.9% sodium chloride is the immediate, life-saving priority. Everything else follows.

By keeping hypercalcaemia in your differential and knowing these critical management steps, you can confidently handle one of the most dangerous metabolic emergencies in medicine.