Hypophosphatemia

Last updated: March 4, 2026

Summary

Hypophosphatemia is defined as a serum phosphate of < 2.5 mg/dL. It is more common in patients with alcohol use disorder and in critically unwell patients, who have high phosphate demands. Particularly in mild deficiency, symptoms can be nonspecific or absent entirely. However, severe hypophosphatemia can cause serious complications such as seizures, respiratory failure, and arrhythmias. Treatment may be oral or intravenous, depending on the severity of the deficiency, and should occur in conjunction with investigation of underlying causes. Supplementation regimens are covered in electrolyte repletion.

Definitions

Serum phosphate of < 2.5 mg/dL (< 0.8 mmol/L) ^[1]
Severe hypophosphatemia occurs at < 1 mg/dL (< 0.32 mmol/L) ^[1]

Etiology

Mechanism	Cause ^[2]^[3]^[4]
Increased renal excretion	FGF23-mediated Post-renal transplant X-linked hypophosphatemia Autosomal dominant hypophosphatemic rickets Fibrodysplasia of bone Tumor-induced osteomalacia ^[5]
Increased renal excretion	Non-FGF23-mediated Hyperparathyroidism Fanconi syndrome Post-hepatic resection hypophosphatemia ^[6] Hereditary hypophosphatemic rickets with hypercalciuria Dialysis ^[7] Gout Hyperglycemia ^[3] Medications ^[8] Diuretic use Theophylline use Rapid intravenous volume expansion Bisphosphonates Glucocorticoids ^[9] Estrogens Imatinib Acyclovir Carbonic anhydrase inhibitors (e.g., acetazolamide)
Insufficient intestinal absorption	Impaired dietary intake/malnutrition Alcohol use disorder ^[8] Malabsorption Total parenteral nutrition (without additional phosphate supplementation) Vomiting Chronic diarrhea Chemotherapy Vitamin D deficiency Premature birth ^[3] Medications ^[8] Phosphate binder use Antacid use
Transcellular phosphate shifts	Refeeding syndrome ^[3] Diabetic ketoacidosis ^[10] Hungry bone syndrome Respiratory alkalosis ^[11] Medications ^[8] Salicylate poisoning Insulin Glucose Beta-2 receptor agonists (e.g., salbutamol) Erythropoietin GM-CSF Catecholamine Dopamine Epinephrine
Extreme catabolic states	Burns Sepsis Trauma Hepatic encephalopathy Acute kidney injury
Pseudohypophosphatemia	Mannitol

Clinical features

Although mild hypophosphatemia rarely causes symptoms, moderate to severe hypophosphatemia is associated with various cardiac, musculoskeletal, neurological, and hematological abnormalities. ^[3]^[4]

Cardiac
Musculoskeletal
- Generalized muscle weakness
- Respiratory muscle dysfunction, which can lead to:
  - Respiratory failure
  - Ventilator dependence and/or difficult ventilator weaning
- Muscle pain (secondary to rhabdomyolysis)
- Loss of bone mass
  - Osteomalacia in adults, rickets in children
  - Bone pain
Neurological
- Fatigue
- Anorexia
- Dysarthria
- Paresthesia, numbness
- Altered mental state (e.g., disorientation)
- Seizures
- Coma
Hematological
- Hemolysis
- Anemia, RBC dysfunction
- Thrombocytopenia, thrombocytopathy
- WBC dysfunction, leading to impaired immune response
Metabolic: reduced insulin sensitivity ^[12]

Treatment

Identify and treat the underlying cause (see etiology of hypophosphatemia).
Consider discontinuation or dose reduction of any contributing medications.
Phosphate supplementation (see repletion regimens for hypophosphatemia)

Electrolyte repletion - Hypophosphatemia

Complications

We list the most important complications. The selection is not exhaustive.

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