Endogenous

• Rhabdomyolysis
• Tumour lysis syndrome
• Crush injury
• Malignant hyperpyrexia

Exogenous

• Phosphate-containing medications (laxatives, fosphenytoin)
• Intestinal uptake (vitamin D toxicity)

Cellular shift

• Acidosis, for example lactic acidosis or diabetic ketoacidosis

Decreased renal clearance

• Reduced glomerular filtration rate
• Acute kidney injury
• Chronic kidney disease

Increased tubular reabsorption

• Hypoparathyroidism or pseudohypoparathyroidism
• Acromegaly
• Bisphosphonates
• Vitamin D toxicity (also increases intestinal absorption)
• Familial tumoral calcinosis

Pseudohyperphosphataemia

• In vitro haemolysis
• Delayed sample delivery