Hypercalcaemia of malignancy

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Malignant hypercalcaemia most often results from tumour secretion of parathyroid-hormone-related peptide, osteoclast activation by bone metastases or myeloma, or calcitriol production in lymphoma. Rarely ectopic parathyroid hormone contributes. These mechanisms can coexist, and extensive bone disease is neither necessary nor sufficient for the diagnosis.

Calcium excess reduces renal concentrating ability, causing polyuria and salt-water loss; dehydration then lowers glomerular filtration and raises calcium further. Gastrointestinal smooth muscle slows, producing constipation and nausea. Neural and muscular function deteriorates, causing fatigue, weakness, confusion and coma, while cardiac conduction changes can lead to a shortened QT interval and arrhythmia.

Ask about oral intake, thirst, urine, vomiting, bowel function, mobility, cognition and recent medicines or supplements. Examine volume status, lying and standing pressure when safe, urine output, mental state, abdomen and neuromuscular function. A mildly raised stable calcium may not explain every symptom, whereas a rapid rise can cause marked illness before an extreme threshold is reached.

Confirm the result rather than relying on one adjusted value. Albumin-correction formulae differ and become unreliable with severe hypoalbuminaemia, acid-base disturbance or critical illness; ionised calcium is then more informative. Measure renal function, phosphate and magnesium and obtain an ECG. Parathyroid hormone should be suppressed in malignancy-related disease; an inappropriately normal or high value suggests coexisting primary hyperparathyroidism.

Restore intravascular volume with 0.9% sodium chloride at a rate matched to blood pressure, renal function, urine output, heart failure and frailty. There is no safe universal litre target. Reassess lungs, oedema, weight and electrolytes repeatedly. Routine furosemide after fluids does not improve calcium clearance sufficiently to justify volume and electrolyte harm, but it can treat genuine fluid overload.

Antiresorptive treatment takes time. Zoledronic acid is a common first choice after renal assessment and usually lowers calcium over two to four days, with a nadir later in the week. Pamidronate is an alternative with dose related to severity and a longer infusion. Both can injure kidneys and cause hypocalcaemia and flu-like symptoms; dental risk matters more with repeated exposure than one emergency dose.

For life-threatening symptoms, calcitonin may provide a rapid temporary reduction while hydration and antiresorptive treatment act. Denosumab can help bisphosphonate-refractory disease and is not cleared renally, but severe prolonged hypocalcaemia is more likely with advanced kidney disease. Glucocorticoids suit calcitriol-driven lymphoma or granulomatous mechanisms. Dialysis is a specialist rescue when severe disease cannot be controlled with fluid because of renal or cardiac failure.

Recurrence is common unless the cancer responds. Explain that treatment may restore alertness, comfort and oral intake, but repeated admissions may offer less benefit as disease advances. Document whether the patient would want another biochemical rescue, what symptoms would prompt testing and how community and oncology teams will respond.

Key points

Suspect hypercalcaemia with new thirst, polyuria, dehydration, constipation, nausea, weakness, drowsiness or delirium, especially in breast, lung, renal, myeloma and advanced squamous cancers.
Severity depends on symptoms, speed of rise, renal function and ECG as well as the number; adjusted calcium above 3.5 mmol/L is a medical emergency.
First-line confirmation uses repeat adjusted calcium with albumin, or ionised calcium when albumin, acid-base state or critical illness makes correction unreliable.
Check ECG, renal function, phosphate, magnesium, full blood count and medicines immediately; stop calcium, vitamin D, thiazide and other contributors where safe.
Initial management is intravenous 0.9% sodium chloride titrated to volume depletion, comorbidity and urine output, with frequent reassessment for overload.
Give an intravenous bisphosphonate after hydration and renal review; zoledronic acid usually works within several days, so clinical and biochemical monitoring must bridge the delay.
Calcitonin can reduce calcium within hours in severe symptomatic disease but loses effect rapidly and is a short bridge, not durable monotherapy.
Denosumab is an option for persistent or recurrent hypercalcaemia despite bisphosphonate, with substantial delayed hypocalcaemia risk, especially in kidney failure or vitamin D deficiency.
Loop diuretics are not routine calcium-lowering therapy; use them only to treat fluid overload after adequate circulating volume is restored.
Before repeated hospital treatment, discuss likely recurrence, anticancer options, expected symptom benefit and whether future episodes should be managed in hospital, community or comfort-focused care.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Humoral tumour secretion

Parathyroid-hormone-related peptide from squamous and other cancers increases bone resorption and renal calcium retention despite suppressed native parathyroid hormone.

Osteolytic tumour activity

Bone metastases and myeloma release cytokines that stimulate osteoclasts locally and systemically, mobilising calcium from the skeleton.

Calcitriol production

Some lymphomas produce active vitamin D outside the kidney, increasing intestinal calcium absorption and sometimes phosphate alongside bone effects.

Coexisting contributors

Dehydration, immobility, thiazides, calcium or vitamin D treatment and primary hyperparathyroidism can amplify a malignant calcium rise.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Accelerated bone resorption
Tumour mediators increase osteoclast formation and activity, releasing skeletal calcium faster than bone and kidney regulation can compensate.
2
Renal concentrating failure
High calcium impairs tubular water conservation, causing polyuria, dehydration and reduced filtration that further limits calcium excretion.
3
Neuromuscular suppression
Raised extracellular calcium alters membrane excitability, producing weakness, reduced reflexes, cognitive slowing, delirium and eventually coma.
4
Gastrointestinal dysmotility
Smooth-muscle and autonomic effects reduce intestinal propulsion, causing anorexia, nausea, abdominal discomfort, constipation and occasionally ileus.
5
Cardiac conduction change
Repolarisation shortens and severe biochemical or accompanying electrolyte disturbance increases the risk of bradyarrhythmia and other rhythm instability.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Renal and thirst pattern

Polyuria, nocturia, intense thirst, dry mucosa, postural symptoms and falling urine output later suggest calcium-driven volume depletion.

Gastrointestinal slowing

New anorexia, nausea, constipation or abdominal distension may precede obvious neurological features and should prompt medicine and metabolic review.

Neurological change

Fatigue, proximal weakness, drowsiness, irritability, confusion and reduced consciousness become more likely as calcium rises quickly or severely.

ECG effect

A shortened QT interval can support the diagnosis, but severe illness may produce bradycardia or other arrhythmia requiring monitored care.

Recurrent malignant pattern

Return of thirst, constipation or confusion weeks after successful treatment often signals tumour-driven recurrence rather than antiemetic or opioid failure alone.

Severe symptomatic elevationRed flag

Adjusted calcium above 3.5 mmol/L, coma, arrhythmia, profound dehydration or acute kidney injury requires urgent monitored treatment.

Red flags requiring action

Reduced consciousness, seizure, aspiration or rapidly progressive delirium indicates severe neurological involvement.
Syncope, bradycardia, shortened QT or another arrhythmia requires monitored cardiac and electrolyte management.
Oliguria, rising creatinine or profound postural hypotension suggests significant renal and volume compromise.
Adjusted calcium above 3.5 mmol/L requires emergency assessment even if the symptom history is incomplete.
Breathlessness, crackles or rising oedema during rehydration indicates fluid overload and requires immediate rate reassessment.
Severe kidney disease magnifies both bisphosphonate nephrotoxicity and denosumab-related hypocalcaemia risk.
Persistent delirium after calcium improves requires a renewed search for infection, medicines, brain disease, retention and other causes.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Repeat adjusted and ionised calciumFirst step
Why
Confirm true elevation with concurrent albumin and use ionised calcium when correction is unreliable because of albumin, pH or critical illness.
Interpretation and limitations
The confirmed concentration, change from baseline and symptoms determine urgency; formula-corrected calcium is not infallible.
02
Immediate renal and electrolyte profile
Why
Measure urea, creatinine, sodium, potassium, phosphate and magnesium before fluid and antiresorptive treatment.
Interpretation and limitations
Volume depletion and renal impairment guide infusion rate, drug choice and monitoring; low phosphate or magnesium can complicate recovery.
03
Twelve-lead ECG and monitoring
Why
Look for shortened QT, bradycardia and other rhythm effects in severe or symptomatic hypercalcaemia.
Interpretation and limitations
Electrical instability, rather than the calcium value alone, determines need for monitored acute care.
04
Parathyroid hormone
Why
Separate suppressed malignant physiology from an inappropriately normal or high parathyroid-driven process.
Interpretation and limitations
Suppression supports non-parathyroid causes; a non-suppressed result prompts assessment for primary hyperparathyroidism or rare mixed disease.
05
Mechanism-directed biochemistry
Why
Use parathyroid-hormone-related peptide, vitamin D metabolites and myeloma studies selectively when the mechanism or diagnosis remains uncertain.
Interpretation and limitations
These tests refine recurrent or unexplained disease but must not delay hydration and urgent calcium-lowering treatment.
06
Cancer assessment and response review
Why
Reassess known tumour burden, skeletal disease and disease-directed options once immediate physiology is stabilised.
Interpretation and limitations
Control of the underlying cancer is the gold standard for preventing recurrence; repeated antiresorptive rescue alone is temporary.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Primary hyperparathyroidism

An inappropriately normal or raised parathyroid hormone with hypercalcaemia suggests autonomous parathyroid disease rather than purely malignant suppression.

Medicine or supplement excess

Thiazides, lithium, vitamin D, calcium and vitamin A can cause or worsen the result and may remain clinically relevant in cancer.

Other delirium causes

Sepsis, opioid toxicity, renal failure, brain disease, urinary retention and dehydration can mimic or compound calcium-related cognitive change.

Immobilisation hypercalcaemia

Prolonged loss of weight bearing increases bone resorption, especially with high skeletal turnover, but alternative malignant mechanisms still require assessment.

Laboratory distortion

Albumin abnormality, sampling error and pH change can make total or adjusted calcium misleading and justify repeat or ionised measurement.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Immediate correctionRestore volume and lower calcium safelyFirst stepHypercalcaemia is symptomatic, rapidly rising or above the severe threshold.

1EscalationConfirm calcium and albumin or ionised calcium, obtain ECG and renal-electrolyte baseline, stop contributing treatment and assess goals and escalation.
2Infuse 0.9% sodium chloride at an individual rate with frequent respiratory, fluid and urine review; treat genuine overload rather than routinely forcing diuresis.
3Give a renal-appropriate intravenous bisphosphonate and consider calcitonin for life-threatening symptoms while monitoring the delayed biochemical response.

02Renal or cardiac constraintAvoid exchanging calcium toxicity for overloadSevere heart failure, kidney failure or oliguria prevents ordinary rehydration or bisphosphonate use.

1Use small reassessed fluid aliquots or a controlled infusion with senior renal, endocrine and acute-oncology input and monitor lungs, weight and urine closely.
2Select calcitonin, adjusted antiresorptive treatment or denosumab only after mechanism, prior therapy and hypocalcaemia risk are reviewed.
3Consider dialysis for refractory life-threatening hypercalcaemia when fluid cannot be given safely or severe renal failure prevents adequate clearance.

03Persistent or recurrent diseaseEscalate antiresorption and address tumourEscalationCalcium remains high after the expected bisphosphonate response or returns repeatedly.

1Check that volume is restored, sufficient response time has elapsed and renal function, vitamin D, phosphate and magnesium are known before redosing.
2Discuss denosumab for bisphosphonate-refractory disease or glucocorticoid treatment for a calcitriol-driven lymphoma mechanism with the relevant specialist.
3Review anticancer treatment, prognosis and the benefit and burden of future admissions and record an agreed recurrence and community-testing plan.

04Comfort-focused decisionTreat symptoms when biochemical rescue no longer fitsThe person is dying, declines hospital treatment or has recurrent disease with little achievable benefit from reversal.

1Explain likely effects and uncertainty, confirm the person's wishes and avoid implying that non-treatment means abandonment.
2Relieve nausea, constipation, thirst, agitation and pain through a reliable route and provide frequent mouth care and proportionate hydration decisions.
3Give carers a clear plan for reduced consciousness and expected dying, review burdensome monitoring and document whether further calcium testing is wanted.

Key medicines and prescribing safety4 treatments · regimens, roles and cautions

Potent osteoclast inhibition produces durable calcium lowering over several days and is a common initial antiresorptive treatment.

Zoledronic acid after volume assessment

A usual adult tumour-hypercalcaemia dose is 4 mg intravenously as a single infusion over at least 15 minutes after adequate hydration; verify renal function, product criteria and local acute-oncology protocol before administration.

Renal toxicity, hypocalcaemia, flu-like reaction and rare jaw osteonecrosis occur; avoid automatic early redosing before the expected nadir and monitor calcium and renal function.

Provides antiresorptive treatment when zoledronic acid is unsuitable or local oncology practice favours pamidronate.

Pamidronate as an intravenous alternative

Use a single intravenous dose selected from 30 to 90 mg according to initial calcium and local protocol, infused slowly with particular attention to renal function and total treatment history.

Response takes days; monitor kidney function, calcium, phosphate and magnesium and do not use a rapid infusion in a frail or renally impaired patient.

Lowers calcium within hours while fluid and antiresorptive treatment take effect in severe neurological or cardiac presentations.

Short calcitonin bridge for severe symptoms

Specialist protocols commonly start salmon calcitonin 4 international units/kg by subcutaneous or intramuscular injection every 12 hours for no more than 48 hours, with escalation only under acute guidance.

Tachyphylaxis develops quickly and nausea, flushing and hypersensitivity occur; availability varies and it must not become prolonged monotherapy.

Blocks RANK ligand and can control persistent osteoclast activity when intravenous bisphosphonate has not produced or maintained response.

Denosumab after bisphosphonate failure

For tumour hypercalcaemia refractory to bisphosphonate, use the licensed oncology regimen under specialist care, commonly 120 mg subcutaneously with loading doses on days 8 and 15 before four-weekly dosing.

Correct vitamin D and electrolyte deficits where safe and monitor prolonged hypocalcaemia closely, especially in severe renal impairment; dental and jaw risk requires review.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Acute kidney injury

Polyuria, vasoconstriction, dehydration and calcium deposition reduce filtration and can make both fluid and antiresorptive treatment more hazardous.

Coma and aspiration

Progressive encephalopathy impairs airway protection and oral medicine delivery and can lead to aspiration, injury and complete dependency.

Arrhythmia

Severe calcium elevation and associated potassium or magnesium disturbance can destabilise cardiac conduction and cause syncope or arrest.

Ileus and nutritional decline

Constipation, nausea and reduced gut motility worsen pain, oral intake, dehydration and absorption of essential symptom medicines.

Treatment-related hypocalcaemia

Bisphosphonate or denosumab can produce symptomatic low calcium, particularly with kidney disease, vitamin D deficiency or extensive osteoblastic response.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

During rehydration track respiratory status, blood pressure, pulse, urine output, fluid balance, weight and oedema rather than prescribing a fixed volume blindly.
Repeat calcium and renal function at a frequency matched to severity, recognising that bisphosphonate response begins after two to four days.
Monitor potassium, phosphate and magnesium and replace deficits according to renal function and local protocol.
Follow mental state, thirst, constipation, nausea, strength and a patient-important function alongside biochemical change.
After calcitonin document the early response and stop within the short protocol window because tachyphylaxis is expected.
After denosumab continue calcium surveillance beyond discharge because hypocalcaemia can be delayed and prolonged.
After recovery agree how recurrent symptoms will be recognised, tested and treated and whether future hospital transfer remains goal concordant.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

The trend matters

A rapid rise can cause severe symptoms at a lower concentration than a chronic stable elevation in another person.

Correction formulae have limits

Ionised calcium is particularly useful when albumin is very low, pH is abnormal or the clinical picture conflicts with adjusted calcium.

Fluid is an active prescription

Rehydration improves renal calcium excretion but needs the same monitoring and stop criteria as any other potentially harmful treatment.

Bisphosphonate response is delayed

A calcium result checked too early can prompt unsafe redosing before the first dose reaches its full effect.

Denosumab changes the risk

Lack of renal clearance does not make it harmless in kidney failure because profound hypocalcaemia becomes more likely.

Recurrence needs advance planning

A successful admission should end with a decision about cancer control, future testing and whether another hospital rescue would be wanted.

11Common pitfallsFrequent interpretation and management errors.

01
Attributing all delirium in advanced cancer to disease progression without checking calcium.
02
Trusting a single albumin-adjusted result when critical illness makes it unreliable.
03
Using a rigid high-volume fluid prescription despite heart or kidney failure.
04
Giving loop diuretic routinely before adequate circulating volume is restored.
05
Expecting an intravenous bisphosphonate to work within hours.
06
Redosing antiresorptive treatment before the expected nadir without specialist review.
07
Using denosumab in advanced kidney disease without a prolonged hypocalcaemia plan.
08
Forgetting magnesium, phosphate and vitamin D context when calcium falls.
09
Stopping assessment once calcium improves despite persistent delirium from another cause.
10
Repeating burdensome admissions without discussing recurrence, prognosis and patient preference.