Specimen Name Result Units Range
Plasma Sodium 120 mmol/L (135-145)
Potassium 3.8 mmol/L (3.5-5.5)
Chloride 87 mmol/L (100-109)
Bicarbonate 20 mmol/L (22-32)
Anion Gap 17 mmol/L (7-17)
Glucose 10.5 mmol/L (3.8-5.5)
Urea 8.2 mmol/L (2.7-7.2)
Creatinine 110 μmol/L (60-110)
Osmolality 281 mmol/kg (275-295)

Obese 49yo male with known IHD.

Xanthelasma on examination
Factitious Hyponatraemia - Hyperlipidaemia

Serum cholesterol : 21 mmol/L
Triglycerides : 81 mmol/L

Hypo-Na+ from hyperlipidaemia usually TG > 50 mmol/L
?? may also result in mild hyperchloraemia acidosis

Actual [Na+] ≈ [Na+]Pl * (measured osmo / calculated osmo)
≈ 120 * (281/259) ≈ 130 mmol/L

Hyponatraemia with normal (slightly low) osmolality aetiology:

  1. drip-arm sample with hypoosmolar IVT
  2. hyperlipidaemia
  3. hyperproteinaemia (low AG)