🧾 Cause	🤒 Clinical Features	🔬 Investigations	💊 Management
🍽️ Refeeding Syndrome	Weakness, respiratory failure, arrhythmias, confusion after feeding malnourished patient	Check PO₄, Ca²⁺, K⁺, Mg²⁺; monitor during refeeding	Slow nutrition, PO/IV phosphate, close monitoring
🍷 Chronic Alcoholism	Weakness, tremor, seizures; often with low Mg²⁺ & K⁺	Serum PO₄, Mg²⁺, K⁺; LFTs, renal function	PO/IV phosphate, nutrition, treat alcohol dependence
💉 Diabetic Ketoacidosis (DKA)	Occurs during insulin therapy: weakness, confusion	Glucose, ketones, PO₄, blood gases, K⁺, Mg²⁺	IV fluids, insulin, phosphate if very low
🦴 Hyperparathyroidism	Bone pain, stones, weakness; hypercalcaemia features	Ca²⁺, PO₄, PTH, urine phosphate	Treat underlying cause ± phosphate support
🥀 Malnutrition	Fatigue, weakness, bone pain, infection risk	Serum PO₄, Ca²⁺, Mg²⁺, albumin; nutrition review	PO/IV phosphate, nutritional support
🧪 Renal Tubular Disorders (e.g., Fanconi)	Polyuria, rickets/osteomalacia, growth delay	PO₄, Ca²⁺, bicarbonate, K⁺; urine glucose, amino acids	PO phosphate, bicarbonate & K⁺ supplements, treat cause
💊 Medications (antacids, diuretics)	Weakness, bone pain, low phosphate symptoms	Check PO₄, Ca²⁺, Mg²⁺; review meds	Stop offending drug, PO phosphate, correct electrolytes
🌬️ Respiratory Alkalosis	Cramps, tetany, confusion from hyperventilation	ABG, PO₄, Ca²⁺, K⁺	Treat cause of hyperventilation, phosphate if severe

🧠 Clinical Features

Asymptomatic → muscle weakness, myalgia, rhabdomyolysis
Seizures, delirium, tremor, paraesthesia
Respiratory failure (weak diaphragm)
Cardiac failure (myocardial weakness)
Osteomalacia, haemolysis, coma

🔗 Associations

Osteomalacia, bone pain, insulin resistance
Glycosuria, hypercalciuria, hypermagnesaemia

🔬 Investigations

U&E, Creatinine
Ca²⁺, Mg²⁺, PO₄, ALP, VBG

💊 Management

Mild (0.6–0.69 mmol/L)
- Usually outpatient: manage cause, diet rich in phosphate
- Oral replacement (e.g. Phosphate Sandoz)
Moderate (0.4–0.59 mmol/L)
- Replace if symptomatic or high risk
- Phosphate Sandoz 1–2 tablets PO TDS
- If severe symptoms → IV phosphate (e.g. 25 mmol over 12h)
Severe (<0.4 mmol/L)
- IV phosphate (e.g. 100 mmol in 500 mL over 8–12h)
- ⚠️ Avoid if hypercalcaemic or oliguric

⚠️ Cautions

Rapid phosphate infusion → hypocalcaemia, calcification
Renally cleared → use with caution in CKD

📚 References

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Hypophosphataemia (Low phosphate)

📏 About

🧬 Aetiology

🩺 Causes