EMed

HypoPhosphataemia: Approach and management in the ED

Mx Doses

Hypophosphataemia = <0.7mmol/L.

  • PO: 1-2 tablets PO4 Sandoz® q8h orally or
  • IV: 20mL ampule POTASSIUM-PO4 DILUTED & slow (not EM slow, proper slow) over 3 hrs

Background

Phosphate is an element which is absorbed through our diets. Found in dairy, grains and meats.

Required for many of the processes in the human body:

  • Essential constituent of cytoplasm
  • Intracellular compounds
  • Bone formation
  • Neuromuscular functioning

Phosphate is absorbed in the GIT distal to the duodenum (aided by Vit D) and excreted via the kidneys (aided by PTH).

Normal serum levels: 0.8 - 1.3mmol/L.

Major stores of phosphate:

  • Bone (85%)
  • Intracellular (in soft tissues) (14%)
  • Extracellular fluid (1%)

Aetiology hypophosphataemia

↓ GI Absorption

  • Alcoholism (commonest)
  • Vitamin D deficiency
  • Malabsorptive disease
  • PO4 binders
    • Ca2+
    • Al3+ / Mg2+ antacids
  • TPN
  • Fasting states (anorexia)

↑ renal excretion

  • Hyperparathyroidism
  • Glycosuria (DKA)
  • Osteomalacia (tumour induced)
  • Renal tubular acidosis
  • Acute tubular necrosis
  • HypoMagnesaemia / HypoKalaemia
  • Multiple myeloma
  • Fanconi syndrome:
    • Proximal tubular dysfxn
    • Wilson's disease (children)
    • Cystinosis (children)

Metabolic conditions

  • Resp. alkalosis
  • Hungry bone synd.
  • DKA
  • Starvation refeeding

Other

  • Medications
  • Anabolic steroids
  • Diuretics
  • Sever burns

Clinical

Mechanism

Early signs PO4 1-2mg/dl

Late signs PO4 <1mg/dl
Dysfunctional
bone metabolism		 ↓ Bone Mineralisation
Bone pain		 Rickets (children)
Osteomalacia (adults)
Intracellular ATP ↓ Myocardial contractility
Proximal muscle weakness
Muscle pain
↑RBC rigidity
Encephalopathy		 Heart Failure
Arrythmias
Rhabdomyolysis
Haemolysis
Seizures/Coma
↓ RBC 2,3 DPG ↑ affinity of Hb for O2 Systemic ischaemia
Leucocyte & platelet dysfunction

Investigations

FE PO4-3 = Urine[PO4] x Plasma[Cr]Urine[Cr] x Plasma[PO4]x100

Management ↓PO4

Treat the underlying cause.

Oral

Phosphate-Sandoz® tablets

Each effervescent tablet contains:

  • Phosphate – 16mmol, Sodium – 20.4mmol

Dose: 1-2 tablets (in 100mL water) q8h.

Diarrhoea is a common side effect (? ↓ dose).

Intravenous

Preparation Sodium Phosphate Addiphos®
Contents Each 20mL ampoule contains:
  • Phosphate 12 mmol
  • POTASSIUM 20 mmol
 Each 20mL ampoule contains:
  • Phosphate 40 mmol
  • POTASSIUM 30 mmol
  • Sodium 30 mmol
Dose One 20 mL ampoule 10-20mL of one ampoule
Preparation Dilute 1 ampoule in ≥500mL of NaCl 0.9% or DW5 Dilute 1 20mL ampoule in 750mL of DW5
Infusion Administer over at least 2 hours:
  • Max. POTASSIUM peripherally is 10mmol/hour
  • Contains POTASSIUM
  • BOLUS INJECTION may be FATAL
 Admin. over 3 - 12 hours
  • Max. POTASSIUM peripherally is 10mmol/hour
  • Contains POTASSIUM
  • BOLUS INJECTION may be FATAL

Content by Dr Tammy Storrier. Last review Dr Tammy Storrier, Dr ÍOS 22/12/25.