Serum phosphorus < normal levels Repeat and if < normal levels Urinary fractional excretion of phosphorus if available (if > 20% or > 10% and hypophosphatemia: referral to a specialist 0.65 – normal level 0.32 – 0.65 mmol/L < 0.32 mmol/L Repeat in 3 months Repeat in 1 month Treat immediately Referral to nephrologist Treat immediately Referral to nephrologist