Hyponatraemia - Diagnosis

How is hyponatraemia diagnosed?

The presence of hyponatraemia is based on the blood levels. However, this may yield little information regarding why the hyponatraemia has occurred. This is why a full assessment has to be undertaken by a healthcare professional. They will be trying to determine whether the hyponatraemia is acute or chronic and be looking for clues as to the underlying cause. They will also decide on whether urgent admission to hospital is required. They will be particularly assessing you for levels of body fluid, which is crucial in determining the cause. The assessment will then help guide them as to the next appropriate tests.

Some of the tests requested include:

  • Blood tests: checking sodium and potassium levels and kidney function. Thyroid function tests and the cortisol hormone (released from the adrenal glands) will also be checked. Blood inflammatory markers, such as C-reactive protein may also be checked - for example, if there are other features of infection. Sodium levels will need to be checked frequently, especially within the first 24-48 hours.
  • Urine sample: looking for sodium levels which are useful in determining the cause.
  • Urine and blood osmolality levels: osmolality is a measure of the solute concentration and may help to determine the cause.
  • Imaging: this depends on the suspected cause and the presentation - for example, a chest X-ray may be required in suspected heart failure, or a computerised tomography (CT) brain scan may be necessary in patients with confusion.
  • Other investigations: some other tests which may be undertaken include a 12-lead heart tracing (electrocardiogram, or ECG), an ultrasound scan of the heart (echocardiogram, or echo) in cardiac failure and, in kidney disease, a renal ultrasound scan.

Did you find this information useful?

Thanks for your feedback!

Why not subcribe to the newsletter?

We would love to hear your feedback!

Dr Gurvinder Rull
Peer Reviewer:
Dr Adrian Bonsall
Document ID:
29395 (v1)
Last Checked:
22 May 2017
Next Review:
26 June 2020

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Patient Platform Limited has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.