Preferred Sample Type


Suitable Specimen Types

  • Plain Spot Urine
  • Serum
  • Li Hep Plasma
1.0 mL blood or urine. (Paed min.vol. 40 uL blood, including K+)

Sample Processing in Laboratory


Sample Preparation


Turnaround Time

1 day

Sample Stability

4 'C


General Information

Sodium is required in the circulation to maintain fluid balance. Concentrations vary in a variety of situations. The following is a synopsis of some of the conditions to illustrate some of those.

Hypernatremiaoccurs in dehydration. For instance, nasogastric protein feeding with insufficient fluids may cause hypernatremia. Hypernatremia without obvious cause may relate to Cushing syndrome, central or nephrogenic diabetes insipidus with insufficient fluids, primary aldosteronism, and other diseases. Severe hypernatremia may be associated with volume contraction, lactic acidosis, azotemia, weight loss, and increased hematocrit as evidence of dehydration. The corrected serum sodium is often high in nonketotic hyperosmolar coma. The corrected serum sodium level calculated in nonketotic hyperosmolar coma: apparent mild hyponatremia with very high glucose may actually mean (corrected) hypernatremia.

Hyponatremia occurs with nephrotic syndrome, cachexia, hypoproteinemia, intravenous glucose infusion, in congestive heart failure, and other clinical entities. Serum sodium is a predictor of cardiovascular mortality in patients in severe congestive heart failure. Hyponatremia without congestive failure or dehydration may occur with hypothyroidism, the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), renal failure, or renal sodium loss. The differential diagnosis of hyponatremia includes Addison disease, hypopituitarism, liver disease including cirrhosis, hypertriglyceridemia, and psychogenic polydipsia. Diuretics and other drugs may cause hyponatremia. Sodium decreasing to levels <115 mmol/L can lead to significant neurological dysfunction with cerebral edema and increased intracranial pressure.

Patient Preparation



Random and 24 hour urine sodiums are also valid

Note: Diuretics, Carbamazepine, Fluoxetin can decrease sodium

Grossly haemolysed samples will not be analysed.

An artifactual rise in sodium due to sample contamination (sodium citrate or Cirta-Lock™) can be identified by measuring both serum chloride and osmolality.  Pseudohypernatraemia (due to hypoproteinaemia) can also be excluded by measuring sodium via a direct ISE method.

Reference Range

Serum: 133 – 146 mmol/L

(Source : Pathology Harmony Recommendations)


  • EQA Scheme?: Yes
  • EQA Status:


The laboratories at Heartlands Hospital, Good Hope Hospital and Solihull Hospital form part of the services provided by University Hospitals Birmingham and are UKAS (United Kingdom Accreditation Service) accredited to the ISO 15189:2012 standard. For a list of accredited tests and other information please visit the UKAS website using the following link:

  • Heartlands, Good Hope and Solihull Hospital pathology laboratories are a UKAS accredited medical laboratory No.8217
  • United Kingdom Health Security Agency laboratory is a UKAS accredited medical laboratory No.8213

Tests not appearing on the UKAS Schedule of Accreditation currently remain outside of our scope of accreditation. However, these tests have been validated to the same high standard as accredited tests and are performed by the same trained and competent staff.

For further test information, please visit the test database:

Protection of personal information - Laboratory Medicine comply with the Trust Data Protection policy and have procedures in place to allow the Directorate and its employees to comply with the Data Protection act  1998 and associated best practice and guidance.

For further information contact Louise Fallon, Quality Manager, 0121 424 1235