Phosphate Imbalances: Causes and Manifestations


  • Primary anion in ICF
    • Essential to function of muscle, red blood cells, and nervous system
    • Involved in acid-base buffering system, ATP production, cellular uptake of glucose, and metabolism of carbohydrates, proteins, and fats
    • Serum levels controlled by parathyroid hormone
    • Maintenance requires adequate renal functioning
    • Reciprocal relationship with calcium
  • Hyperphosphatemia
    • High serum PO43- caused by
      • Acute kidney injury or chronic kidney disease
      • Chemotherapy
      • Excess intake of phosphate or vitamin D
      • Hypoparathyroidism
    • Manifestations
      • Neuromuscular irritability and tetany (hypocalcemia)
      • Calcified deposits in soft tissue like, arteries, skin, kidneys, and corneas (can cause organ dysfunction)
      • Numbness and tingling in extremities and region around mouth
      • Hyperreflexia, muscle cramps
      • Tetany, seizures
    • Management
      • Identify and treat underlying cause
      • Restrict foods and fluids containing phosphorus
      • Oral phosphate-binding agents
      • Volume expansion and forced diuresis
      • Correct any hypocalcemia
      • Hemodialysis
  • Hypophosphatemia
    • Low serum PO43- caused by
      • Malnourishment/malabsorption/diarrhea
      • Use of phosphate-binding antacids
      • Inadequate replacement during parenteral nutrition
    • Manifestations
      • CNS depression
      • Muscle weakness and pain
      • Respiratory and heart failure
      • Rickets and osteomalacia
      • Cardiac problems (dysrhythmias, heart failure)
      • Osteomalacia, rickets
      • Rhabdomyolysis
    • Management
      • Oral supplementation
      • Ingestion of foods high in phosphorus
      • IV administration of sodium or potassium phosphate

Phosphate Imbalances: Causes and Manifestations

Hyperphosphatemia (PO43− >4.4 mg/dL [1.42 mmol/L])

Hypophosphatemia (PO43− <2.4 mg/dL [0.78 mmol/L])


  • Renal failure
  • Malabsorption syndromes
  • Phosphate enemas (e.g., Fleet Enema)
  • Chronic diarrhea
  • Excessive ingestion (e.g., phosphate-containing laxatives)
  • Malnutrition, vitamin D deficiency
  • Rhabdomyolysis
  • Parenteral nutrition
  • Tumor lysis syndrome
  • Chronic alcoholism
  • Thyrotoxicosis
  • Phosphate-binding antacids
  • Hypoparathyroidism
  • Diabetic ketoacidosis
  • Sickle cell anemia, hemolytic anemia
  • Hyperparathyroidism
  • Hyperthermia
  • Refeeding syndrome
  • Respiratory alkalosis


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