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Electrolytes
Phosphate (inorganic) (PO4)
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This is the date the draft was written, not a medical review date.
Serum inorganic phosphate reflects renal handling, intestinal absorption and shifts between the intracellular and extracellular compartments; it is regulated by PTH, vitamin D and FGF23.
Reference interval
| Conventional (mg/dL) | SI (mmol/L) | |
|---|---|---|
| Adults | 2.8–4.5 mg/dL | 0.9–1.45 mmol/L |
Specimen: Serum · Conventional × 0.3229 = SI
Causes of high values
Chronic kidney disease (the commonest cause), hypoparathyroidism, vitamin D excess, tissue breakdown (rhabdomyolysis, tumour lysis), and acidosis. Children have physiologically higher values.
Causes of low values
Primary hyperparathyroidism, vitamin D deficiency, refeeding syndrome, alcohol use disorder, respiratory alkalosis, insulin therapy, malabsorption and renal tubular losses.
Pre-analytical and method notes
Values show diurnal variation (lowest in the late morning) and rise after meals; haemolysis and delayed separation raise them. Reference intervals are age-dependent and vary by laboratory; results may be reported as phosphorus.
References
- Rifai N, Horvath AR, Wittwer CT. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Elsevier, 6th edition (2018) — Tier 3 (textbook)
- Loscalzo J, et al.. Harrison's Principles of Internal Medicine. McGraw-Hill, 21st edition (2022) — Tier 3 (textbook)
- KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Disease: Improving Global Outcomes (2013) — Tier 2 (guidelines / primary literature)
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