REASONING GP · Clinical algorithm · Quick reference

Hypercalcaemia in adults — triage and diagnostic approach

Two causes account for about 90% of cases — primary hyperparathyroidism and malignancy — and the PTH separates them in one test. Correct for albumin, then act on the adjusted value.
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AdultsLab resultAdjusted Ca²⁺ above 2.60v1.0 · Sep 2026
Core rule. Use the albumin-adjusted calcium, never the total — a low albumin hides significant hypercalcaemia and a high one invents it. Then: adjusted Ca²⁺ above 3.40 mmol/L is an emergency at any level of wellness, and any symptomatic hypercalcaemia needs same-day assessment — drowsiness, confusion, vomiting or dehydration, because the calcium and the dehydration drive each other upward. The single most useful next test is a PTH on a fresh uncuffed sample. A raised or inappropriately normal PTH means primary hyperparathyroidism; a suppressed PTH means look for malignancy, and look urgently.
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On seeing the result: is this an emergency now? Arrange emergency admission — 999 or immediate discussion with the acute team
Adjusted Ca²⁺ above 3.40 mmol/L, however well the patient seems — IV fluids and bisphosphonate are needed, and the level rises further without them · adjusted Ca²⁺ above 3.00 with any symptom: drowsiness, confusion, delirium, severe weakness, persistent vomiting, dehydration, abdominal pain, or reduced urine output · reduced GCS, seizure or coma · cardiac features — bradycardia, a shortened QT interval, arrhythmia, or the patient is on digoxin (hypercalcaemia precipitates toxicity) · severe dehydration or acute kidney injury with a rising creatinine · known or suspected malignancy with a rapid rise. Hand over the adjusted calcium with albumin, previous values and dates, U&E, the drug list and the fluid status.
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Adjust, grade, then send one test The adjusted value decides urgency; the PTH decides the cause

Adjust first

Always use the laboratory's albumin-adjusted (corrected) calcium. A low albumin — common in malignancy, liver disease, malnutrition and inflammation — makes the total calcium look normal while the adjusted value is clearly raised. If only an ionised calcium is available, use that. Confirm on a repeat uncuffed sample before labelling anyone, unless the level or symptoms demand action now.

Grade by adjusted value

Above 3.40: emergency admission at any level of wellness. 3.00–3.40: same-day assessment — admission if symptomatic, dehydrated or with AKI. 2.80–2.99: urgent primary-care investigation within days. 2.61–2.79: confirm and investigate in primary care. Symptoms override the number in either direction.

Send the PTH — the one test that splits the diagnosis

A PTH with a paired calcium on a fresh sample. Raised or inappropriately normal PTH: primary hyperparathyroidism (or tertiary, or familial hypocalciuric hypercalcaemia). Suppressed PTH: malignancy, myeloma, vitamin D toxicity, sarcoidosis, thyrotoxicosis or immobility — and it should prompt an urgent search for cancer.

Symptoms to ask about directly

"Stones, bones, groans and psychic moans": renal colic, bone pain, constipation and abdominal pain, low mood, poor concentration. Also polyuria and thirst (the calcium causes a concentrating defect, hence the dehydration), fatigue, muscle weakness, anorexia, vomiting, and unexplained weight loss.
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Red-flag screen: trigger → concern → destination → what to do before handover One row is enough; do not add up reassuring features
Trigger / red flagLeading concern · destinationDo now · do not delay
Adjusted Ca²⁺ above 3.40 mmol/L, or above 3.00 with drowsiness, confusion, vomiting, dehydration or reduced urine output; reduced GCS or seizure. Hypercalcaemic crisis · needs IV saline and an IV bisphosphonate
Emergency admission now		 This is a self-amplifying problem: hypercalcaemia causes polyuria, the dehydration reduces calcium excretion, and the level climbs further — so the patient deteriorates while waiting. Oral rehydration at home is not treatment above 3.40. Stop calcium and vitamin D supplements, thiazides and lithium now, and say what was stopped. Send the adjusted calcium with albumin, U&E and the previous values.
Cardiac or drug risk: bradycardia, shortened QT, arrhythmia, or the patient takes digoxin. Arrhythmia · digoxin toxicity precipitated by hypercalcaemia
Emergency admission; ECG now		 Hypercalcaemia potentiates digoxin and can precipitate toxicity at a previously stable dose. ECG before or alongside transfer. Do not continue digoxin unreviewed, and do not wait for a repeat calcium to act.
Hypercalcaemia with acute kidney injury: creatinine rising, eGFR falling, oliguria, or a patient unable to maintain oral intake because of vomiting. Hypercalcaemic AKI
Emergency admission now		 Dehydration and AKI make the hypercalcaemia worse and vice versa; this needs IV volume replacement with monitoring, not oral fluids and a repeat next week. Hold ACE inhibitors, ARBs, NSAIDs, diuretics and metformin as appropriate and record what was held (NG148).
Adjusted Ca²⁺ 3.00–3.40 mmol/L in a patient who is alert, hydrated and without AKI. Moderate-to-severe hypercalcaemia needing assessment today
Same-day clinical assessment and bloods		 Assess hydration, GCS and orientation face to face; this cannot be judged on the telephone. Send PTH with a paired calcium, U&E, phosphate, magnesium, ALP, vitamin D, FBC, ESR or CRP, LFTs and TSH the same day. Stop calcium and vitamin D supplements, thiazides and lithium. Encourage oral fluids and repeat within 24–48 hours — with a named person to look at the result.
Known or suspected malignancy with a raised calcium — breast, lung, myeloma, renal, prostate, head and neck, lymphoma — or a rapid rise on serial results with a suppressed PTH. Malignant hypercalcaemia · bone metastases · PTHrP-secreting tumour
Same-day oncology or acute assessment		 Malignant hypercalcaemia rises quickly and carries a poor prognosis untreated; it is an oncological emergency, not a metabolic finding to monitor. Contact the patient's oncology team directly rather than arranging routine review. In a patient already on the palliative pathway, the treatment decision belongs with the specialist team and the patient's wishes.
Suppressed PTH with no obvious cause, or hypercalcaemia with high-dose vitamin D, calcium carbonate, lithium, a thiazide, teriparatide, excess vitamin A, or antacid or milk excess. Non-parathyroid hypercalcaemia · drug or supplement cause
Same-day review of the drug; urgent investigation of the cause		 Ask directly about over-the-counter supplements and high-dose vitamin D — these will not be on the repeat prescription and the patient may not volunteer them. Stop the culprit, and recheck at 1–2 weeks. A suppressed PTH that does not resolve on stopping supplements still needs the malignancy and granulomatous workup below.
Granulomatous or endocrine features: breathlessness with bilateral hilar changes, erythema nodosum or uveitis; tremor, weight loss and heat intolerance; recent immobility or a long bed-bound period; postural hypotension with fatigue. Sarcoidosis · tuberculosis · thyrotoxicosis · immobilisation · adrenal insufficiency
Same-day or urgent investigation depending on severity		 Send TSH, ACE, chest X-ray and vitamin D metabolites as indicated. These causes also present with a suppressed PTH, so they are on the same limb of the algorithm as malignancy and must not be assumed until cancer has been addressed.
Hypercalcaemia with a myeloma or cancer feature: unexplained bone pain (especially back pain), fractures on minimal trauma, anaemia, weight loss, fatigue, unexplained renal impairment, a raised ESR or plasma viscosity, or hypercalcaemia at 60 or over with no parathyroid explanation. Myeloma · metastatic bone disease · other malignancy
Very urgent FBC, calcium, plasma viscosity/ESR and protein electrophoresis with Bence Jones protein — within 48 hours; urgent suspected-cancer referral if positive · NICE NG12		 NG12: in anyone 60 or over with hypercalcaemia or leucopenia and a presentation consistent with possible myeloma, arrange a very urgent FBC, calcium, plasma viscosity or ESR and serum protein electrophoresis with urinary Bence Jones protein — within 48 hours — and refer on the urgent suspected-cancer route if the results suggest myeloma. Hypercalcaemia with unexplained bone pain or renal impairment should not be investigated at a leisurely pace. Normal results with persisting symptoms still need review and a decision on referral.
Safety rule. Never act on the total calcium — use the albumin-adjusted value. Wellness is not reassurance above 3.40. Do not give a loop diuretic at home to "flush out" calcium: it worsens the dehydration that is driving the level. Do not give IV fluids without monitoring in a patient with heart failure or CKD. And a suppressed PTH is not a benign finding — it is the limb of the algorithm that leads to cancer.
Colour is semantic: red = emergency now · amber = same-day assessment · blue = define/assess · green = primary-care management · purple = uncertain / specialist route (including 2WW). Continued on page 2: investigation, classification, cause classifier, routine referral, primary-care management, endpoint.
REASONING GP · Hypercalcaemia in adults — triage and diagnostic approach
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Assessment and investigation Hydration and cognition cannot be assessed remotely

Assess

GCS and orientation; hydration — lying and standing BP, pulse, mucous membranes, skin turgor, urine output. Examine for a breast lump, chest signs, nodes, an abdominal mass, bone tenderness (spine, ribs), prostate if indicated, goitre.

The bloods

PTH with a paired calcium on a fresh uncuffed sample, plus albumin · U&E · phosphate, magnesium · ALP · vitamin D · FBC · ESR or plasma viscosity · LFTs · TSH · and in the 60-and-overs, protein electrophoresis with Bence Jones protein (NG12). Add a 24-hour urinary calcium if FHH is possible.

Reading them together

Raised PTH, low-normal phosphate: primary hyperparathyroidism. Suppressed PTH, raised ALP: bone metastases. Suppressed PTH with anaemia, renal impairment, raised ESR: myeloma — electrophoresis urgently. Raised PTH in CKD: tertiary. Raised PTH, low urinary calcium: FHH — no surgery.

Do not

Do not diagnose on a cuffed sample alone, or label hyperparathyroidism without a PTH. Do not repeat the calcium for months with the PTH unmeasured. Do not skip electrophoresis in an older patient with bone pain — that is the missed myeloma.
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Classify: three exits, not two "Mildly raised calcium, repeat in 6 months" is only safe once the PTH is known

Emergency or same-day

Above 3.40, above 3.00 with symptoms, AKI, cardiac features or digoxin, or malignancy with a rapid rise. Output: destination, adjusted calcium with albumin, hydration, U&E, drugs stopped.

Mild, PTH-driven, managed in primary care

Adjusted Ca²⁺ 2.61–2.79, asymptomatic, normal renal function, PTH raised or inappropriately normal, no cancer feature. Output: diagnosis, drugs stopped, monitoring interval, escalation thresholds.

Unclassified or PTH-suppressed

Suppressed PTH with no cause found, persisting after supplements stop, or a raised calcium with unexplained bone pain. Output: state the uncertainty, take the §6 route or the NG12 panel.
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Cause classifier: the PTH splits it in two Only once the urgency is settled
Primary hyperparathyroidism
PTH raised or inappropriately normal		The commonest cause in the community, usually incidental in an asymptomatic older woman: mildly raised calcium, low-to-normal phosphate, raised or unsuppressed PTH. Assess the end-organ consequences — renal function, stones on imaging, DEXA — because these, not the calcium alone, decide whether surgery is offered (NG132).
Malignancy
PTH suppressed		Must be excluded first when the PTH is low: PTHrP secretion (squamous lung, renal, breast, head and neck), osteolytic metastases (breast, lung, prostate, renal), and myeloma — hypercalcaemia with anaemia, renal impairment and bone pain. Typically higher, faster-rising, with a raised ALP. Investigate urgently; do not monitor.
Drugs, then the granulomatous and endocrine causes
PTH usually suppressed		Drugs — the commonest reversible cause in primary care: high-dose vitamin D and calcium carbonate (including antacids), thiazides, lithium (raises PTH), teriparatide, excess vitamin A. Most often missing from the drug history because the patient buys it — ask directly. Then: sarcoidosis and tuberculosis (excess 1,25-dihydroxyvitamin D), thyrotoxicosis, adrenal insufficiency, phaeochromocytoma — all on the same suppressed-PTH limb as malignancy, so they do not remove the need to look for cancer.
FHH, tertiary, immobility and spuriousFamilial hypocalciuric hypercalcaemia: lifelong mild hypercalcaemia, raised or normal PTH, low 24-hour urinary calcium, family history, no end-organ damage — needs no treatment and no surgery, and mistaking it for primary hyperparathyroidism leads to an unnecessary parathyroidectomy. Tertiary: long-standing CKD, raised PTH with a high phosphate. Immobilisation: especially in Paget's or prolonged bed rest. Spurious: a cuffed sample, dehydration or a high albumin — hence the adjusted value on a repeat.
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Refer routinely from this consultation Not same-day — the cases that leave by letter; §7 is what primary care does today
Confirmed primary hyperparathyroidism → endocrinology for parathyroidectomy, the only curative treatment (NG132). Refer rather than monitor where the adjusted calcium is 2.85 mmol/L or above, or there is symptomatic disease, a renal stone, renal impairment, osteoporosis or a fragility fracture, or the patient is under 50; send the PTH, paired calcium, U&E, vitamin D, urinary calcium and DEXA in the letter · asymptomatic and not meeting those criteria → discuss and monitor, cinacalcet only where surgery is unsuitable · suspected FHH → endocrinology for genetic confirmation, to prevent an unnecessary operation · suspected sarcoidosis → respiratory · tertiary hyperparathyroidism → renal · osteoporosis on DEXA → treat alongside (NG146).
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The only decisions that belong in this consultation What primary care manages today — mild, asymptomatic, PTH-driven hypercalcaemia
Confirm on the adjusted value, and send the PTHRepeat the calcium uncuffed with albumin and send a PTH with a paired calcium at the same time — not after another six months of watching the calcium. Add U&E, phosphate, ALP, vitamin D, FBC, ESR and, in the 60-and-overs, the NG12 48-hour myeloma panel. Without a PTH there is no diagnosis, only a number.
Stop the culpritsStop calcium and vitamin D supplements (prescribed and bought), calcium-containing antacids and thiazides, switching antihypertensive class. Review lithium with mental-health input rather than stopping it unilaterally, and check the level. Review digoxin. Recheck at 1–2 weeks. Encourage 2–3 litres of fluid daily if cardiac and renal function allow, since dehydration raises the calcium further, and avoid prolonged immobility — but do not give a loop diuretic at home, which worsens the dehydration driving the level.
Assess the end-organ damage — it decides the referralArrange renal function, DEXA, and imaging for renal stones where indicated. These findings, not the calcium alone, determine whether parathyroid surgery is offered, so the letter is far more useful with them (NG132). Treat confirmed osteoporosis in parallel (NG146).
Monitor and the escalation rule — write it downFor mild asymptomatic disease: adjusted calcium, U&E and eGFR at least annually, DEXA periodically. Write the triggers down: adjusted Ca²⁺ above 3.40, or above 3.00 with drowsiness, confusion, vomiting or dehydration → emergency admission; 2.85 or above, or new symptoms, stones, fractures or falling eGFR → endocrine referral.
What not to doDo not act on a total calcium. Do not monitor a suppressed PTH — that is the cancer limb. No loop diuretic at home. Do not restart the thiazide. Do not file a raised calcium as "borderline" with no PTH and no reviewer — that is how myeloma is missed for years.
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Endpoint and documentation Finish with one of four conclusions

1 · Emergency

Admission arranged; adjusted calcium with albumin, previous values, symptoms, GCS, hydration, U&E, ECG if done, drugs stopped.

2 · Same-day

Assessment today; hydration and cognition recorded; PTH with paired calcium and the panel sent; supplements and thiazide stopped; repeat in 24–48 h.

3 · Mild, PTH-driven, managed

Adjusted level, PTH result and cause recorded; drugs stopped; end-organ assessment arranged; monitoring interval and escalation thresholds written down.

4 · Unclassified or PTH-suppressed

Uncertainty stated; NG12 48-hour panel or §6 referral sent, with date; imaging arranged; review owner and timeframe.
Why primary-care management is safe today, in one line: the value is the albumin-adjusted one, confirmed on a repeat uncuffed sample · 2.61–2.79 mmol/L · asymptomatic — no drowsiness, confusion, vomiting, thirst or polyuria · hydrated, normal renal function · PTH raised or inappropriately normal, so the malignancy limb is not in play · supplements, thiazide and lithium reviewed · NG12 considered and the 48-hour panel sent in the 60-and-overs · end-organ assessment arranged · monitoring interval and escalation thresholds written down with a named reviewer. Safety-net wording: contact us or 111 the same day if you become confused, unusually drowsy or weak, start vomiting or cannot keep fluids down, become very thirsty or pass much more urine than usual; call 999 for a fit or collapse. Keep fluids up, take no calcium or vitamin D unless agreed, and attend the tests even if you feel well.
Remote and result-handling limitation. Hydration and cognition cannot be judged on the telephone, so an adjusted calcium above 3.00 needs a face-to-face assessment. Convert to face-to-face or emergency assessment where the patient cannot attend, is vomiting or unable to drink, is frail or lives alone, a relative reports confusion, or the result arrives out of hours — above 3.40 must never sit in an inbox overnight.
Clinical decision support only; follow local acute-transfer, renal and prescribing policies and check doses against the current BNF. Source hierarchy: NICE guidelines and CKS first, then BNF/MHRA for doses and safety, then national specialty guidance. Sources: NICE NG132 Hyperparathyroidism (primary) · NG12 Suspected cancer (May 2025) · NG146 Osteoporosis · NG148 Acute kidney injury · NG203 Chronic kidney disease · NICE CKS Hypercalcaemia, Primary hyperparathyroidism · Society for Endocrinology emergency guidance on acute hypercalcaemia · UK Kidney Association · BNF · MHRA. Review after any guidance or medicines-safety update, otherwise every 6 months. © Reasoning GP · gpreasoning.uk