# Hypercalcemia: read the whole pattern

Andrew Bland, MD, FACP, FAAP · October 21, 2026

## Start with PTH in the context of calcium

A PTH inside its reference interval is not necessarily appropriate: high calcium should suppress it. A clearly suppressed PTH directs the workup toward PTH-independent causes. Use the assay and clinical context rather than a universal cutoff.

## The vitamin D tests answer different questions

25-hydroxyvitamin D reflects stores and exposure. 1,25-dihydroxyvitamin D is the active hormone; an elevated value with suppressed PTH can suggest extrarenal production. A low 25-hydroxy level does not exclude calcitriol-driven hypercalcemia.

## Phosphate and alkaline phosphatase are supporting clues

AKI and CKD can raise phosphate and blur a typical phosphaturic pattern. Total alkaline phosphatase includes liver and bone sources; normal ALP does not exclude myeloma or lytic bone disease. These tests help interpret a mechanism but cannot identify one alone.

## The table is a pattern guide, not an order set

Not every patient needs all seven tests at once. Confirm calcium, assess symptoms and volume, interpret PTH, then choose PTHrP, vitamin D metabolites and monoclonal-protein testing as indicated. Mixed mechanisms and drug exposures can coexist.

## Additional causes remain part of the differential

Thiazides can unmask primary hyperparathyroidism; lithium can shift calcium sensing. Vitamin A excess, immobilization, thyrotoxicosis, adrenal insufficiency and pediatric syndromes require the appropriate history and targeted tests. None has a single obligatory seven-test signature.

## Laboratory comparison

|Mechanism|Ca|PO4|ALP|1,25 D|25 D|PTH|PTHrP|Interpretation|
|---|---|---|---|---|---|---|---|---|
|Primary hyperparathyroidism|↑|↓ or N|N or ↑|N or ↑|Variable|↑ or inappropriately N|Not elevated|PTH should be suppressed by high calcium; check urine calcium in the appropriate setting.|
|PTHrP-mediated malignancy|↑|↓ or N|Variable|↓ or N|Variable|↓|↑|PTHrP mimics some PTH effects. An abnormal SPEP is not required.|
|Calcitriol-mediated disease|↑|N or ↑|Variable|↑|N or ↓|↓|Usually not elevated|Consider lymphoma or granulomatous disease; the lab pattern does not identify which.|
|Vitamin D₂/D₃ excess|↑|N or ↑|N or ↓|N or ↑|Markedly ↑|↓|Not elevated|Excess nutritional vitamin D raises 25(OH)D; active-vitamin-D medications are a different exposure.|
|Osteolytic malignancy / myeloma|↑|Variable|Variable; often N in myeloma|↓ or N|Variable|↓|Usually not elevated|ALP can remain normal despite lytic lesions; evaluate monoclonal protein when indicated.|
|Calcium–alkali syndrome|↑|↓ or N; affected by kidney function/intake|Usually N|↓ or N|Variable|↓|Not elevated|Calcium/alkali exposure, alkalosis and AKI; medication history matters.|
|Tertiary hyperparathyroidism|↑|Often ↑ in advanced CKD; may fall after transplant|Variable|Variable; often low in advanced CKD|Variable|Markedly ↑|Not elevated|Longstanding secondary HPT becomes autonomous; CKD alone does not prove this diagnosis.|
|Familial hypocalciuric hypercalcemia|Usually mildly ↑|N or ↓|Usually N|Variable|Variable|N or mildly ↑|Not elevated|Lifelong/familial pattern and relative hypocalciuria; CKD, low vitamin D and thiazides confound urine calcium.|

## Sources

- [ARUP Laboratories: hypercalcemia testing algorithm](https://arupconsult.com/sites/default/files/Hypercalcemia%20Testing%20algorithm.pdf)
- [Fifth International Workshop: primary hyperparathyroidism (2022)](https://pubmed.ncbi.nlm.nih.gov/36245251/)
- [Endocrine Society: hypercalcemia of malignancy guideline](https://www.endocrine.org/clinical-practice-guidelines/hypercalcemia)
- [Society for Endocrinology: emergency management of acute hypercalcaemia](https://pubmed.ncbi.nlm.nih.gov/27935816/)
- [Alkaline phosphatase in myeloma and solid cancers with bone lesions](https://pubmed.ncbi.nlm.nih.gov/33304804/)
- [Vitamin D intoxication and hypercalcemia](https://pubmed.ncbi.nlm.nih.gov/8548936/)