Diagnosing a cough

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Most acute/short-terms coughs will go away on their own, and many people don’t even go and see a doctor. 

“Cough remedies” such as cough mixtures and lozenges don’t speed up the healing process, but may reduce the cough intensity to some degree. Thus, the cause of the cough is often never really evaluated as most of us self-medicate our coughs and colds.

If, however, the simple cough doesn’t go away, or if it’s accompanied by more than just a runny nose, a doctor is often consulted.

The starting point in diagnosing the cause of the cough, and thus appropriate treatment, is taking a detailed history: 

  • When did the cough start? 
  • When does it occur (e.g. day/night, after food, when lying/standing)?  
  • Does anything come up when you cough (in other words, is it a “productive” cough)? 
  • What does the phlegm or mucus look like, and how much comes up?Is anything else associated with the cough (e.g. fever, weight loss, night sweats)? 

These are the most important questions your doctor will ask you. 

It’s often more important and helpful to get the whole picture of the cough with a consultation than doing any special investigations. These investigations are usually only used just to confirm the cause – for example, a foreign body seen on a chest X-ray after the cough began when a Lego piece disappeared down a child’s throat!

Acute cough

If your doctor suspects:

Investigations your doctor might consider:

A foreign body


Heart failure

Blood tests
ECG (electrocardiogram)

Exacerbation of asthma / COPD

Lung-function tests
X-ray to exclude infection

Infective cause

Sputum test for tuberculosis
Blood tests in certain cases

Chronic cough

If your doctor suspects:

Investigations your doctor might consider:

Infective causes (excluding TB)

Sputum testing


Sputum testing
Mantoux testing (in children)


Lung-function testing
Bronchodilator testing

GORD-related cough

24-hour oesophageal pH monitoring

Cough of cardiac origin


Interstitial lung disease

CT scan

A clinical examination usually gives a healthcare practitioner a very clear indication of the cause of the cough. Special investigations will be considered by your doctor if the cause of the cough remains unclear, or to support a diagnosis.

Read more:
Treating a cough

Reviewed by Professor Richard van Zyl-Smit, Head of the Lung Clinical Research Unit at the University of Cape Town. MBChB, MRCP(UK), Dip HIV(Man), MMED, FCP(SA), Cert Pulm(SA), PhD. February 2018. 

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