What is a normal phosphorus level?

Normal phosphorus is 3.0–4.5 mg/dL. Use your facility's reference range.

Phosphorus (PO₄³⁻)

Muscle weakness — including respiratory muscles, Confusion, Difficulty weaning from the vent.

Mostly shows as LOW-calcium signs (tingling, spasm), Itching in renal patients, Calcium-phosphate deposits long-term.

Normal 3.0–4.5 mg/dL

Why it matters

Energy (ATP) and cell membranes. See-saws with calcium.

LOW — Hypophosphatemia (< 3.0)

Causes

REFEEDING syndrome — starting nutrition on the malnourishedAlcohol use disorderDKA treatmentAntacid binding

Signs

Muscle weakness — including respiratory musclesConfusionDifficulty weaning from the vent

Nursing actions

Starting feeds on a malnourished/alcohol-use patient: watch phos daily for the first days
Watch work of breathing at severe lows
Replace per orders

HIGH — Hyperphosphatemia (> 4.5)

Causes

Renal failureTumor lysis syndromeRhabdomyolysis

Signs

Mostly shows as LOW-calcium signs (tingling, spasm)Itching in renal patientsCalcium-phosphate deposits long-term

Nursing actions

Phosphate binders WITH meals (they bind food phosphorus — timing is the whole point)
Renal diet teaching
Watch the calcium

Source: Ignatavicius, Medical-Surgical Nursing, 10th ed.Reference only — verify against your facility's policy.