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Electrolytes & Minerals

Phosphate (Phosphorus)

Normal range 2.5-4.5 mg/dL (0.81-1.45 mmol/L SI). Specimen: Serum.

Also known as: serum phosphorus, PO4, inorganic phosphate.

2.5-4.5 mg/dLCritical value: read below

Reference range

Conventionalmg/dL
2.54.5
SImmol/L
0.811.45

Combined adult band. LabVals does not publish separate men's, women's, or pediatric ranges for Phosphate (Phosphorus); those can be narrower than the band shown.

Phosphate (Phosphorus) reference range, specimen, and conversion details
SpecimenSerum
Conventional range2.5-4.5 mg/dL
SI range0.81-1.45 mmol/L
Conversion factor×0.323 (conventional → SI)
Critical value< 1.0 mg/dL
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Convert any Phosphate (Phosphorus) result between units on the unit converter.

What is the normal range for Phosphate (Phosphorus)?

The standard teaching reference range for Phosphate (Phosphorus) is 2.5-4.5 mg/dL in conventional units, or 0.81-1.45 mmol/L in SI units. This value is measured in serum.

What is a critical Phosphate (Phosphorus) value?

For Phosphate (Phosphorus), the commonly taught critical (panic) value is: < 1.0 mg/dL. Critical results are reported to the provider immediately under your facility's policy.

Source: Adult reference values compiled from Pagana & Pagana, Mosby's Diagnostic and Laboratory Test Reference, and Fischbach & Dunning, A Manual of Laboratory and Diagnostic Tests. Reference ranges vary by laboratory, method, age, sex, and population - always use the range printed on the actual result.

At the bedside

Nursing considerations

  • Phosphate moves inversely to calcium.
  • Watch for severe hypophosphatemia during refeeding - it can cause respiratory failure.
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