When Does a Cough Need a Doctor? Red Flag Checklist

Most coughs after a respiratory infection last around three weeks and resolve without treatment. The question is which ones do not fit that pattern.

Go to the emergency room for

• Severe difficulty breathing, or inability to speak a full sentence
• Blue or grey lips, face, or fingertips
• Coughing up a significant amount of blood
• Chest pain with breathlessness
• Confusion or extreme drowsiness
• Choking, or a cough that began after inhaling something
• Severe throat swelling or noisy breathing on inhaling
• Oxygen saturation below 92%

Call a doctor the same day for

• Fever above 101°F with a cough for more than three days
• Breathlessness on light activity such as walking across a room
• Streaks of blood in mucus, or rust-coloured mucus
• Chest pain that worsens on deep breath
• Fever that returned after you had recovered — a key warning sign for pneumonia
• Wheezing that is new for you
• Coughing that causes fainting
• You have COPD, asthma, heart failure, or a weakened immune system and the cough is worsening

Book an appointment for

• A cough lasting more than three weeks without clear improvement
• A cough getting worse rather than better after the second week
• A cough with unexplained weight loss
• A cough with night sweats
• A cough with hoarseness lasting more than three weeks
• A cough with swallowing difficulty
• A cough disrupting sleep every night for weeks
• A persistent cough in a current or former smoker

Usually fine to manage at home

• A cough in the first two to three weeks after a cold or flu — see post-viral cough
• A cough that is gradually improving even if slowly
• A cough with clear mucus and no fever
• A cough triggered only by cold air or talking

The three-week rule and why it exists

Coughs are classified as acute (under three weeks), subacute (three to eight weeks), and chronic (over eight weeks). Three weeks is the point at which a simple post-viral explanation becomes less likely and other causes deserve investigation.

The main causes of a cough lasting beyond eight weeks in non-smokers are postnasal drip, asthma, and acid reflux — together accounting for the large majority of cases. ACE inhibitor blood pressure medication is a fourth common cause that is frequently missed; drugs ending in “-pril” cause a dry cough in roughly one in ten users. See dry cough versus wet cough.

What to tell your doctor

Come prepared with:

• How long the cough has lasted, and whether it began with an illness
• Dry or productive, and if productive, the colour and amount
• What triggers it and what time of day it is worst
• Any fever, breathlessness, chest pain, or weight loss
• Your complete medication list — particularly any blood pressure medication
• Smoking or vaping history
• Any occupational exposure to dust, chemicals, or fumes

That list will get you a much better consultation than “I have had a cough for a while.”

What they may do

Listen to your chest, check oxygen saturation, and depending on findings order a chest X-ray, spirometry to test lung function, or a trial of treatment for reflux or asthma. A trial of treatment is often used diagnostically — if it works, that confirms the cause.

What will not help

Repeated antibiotic courses for a viral or post-viral cough. If you have had two or more courses with no benefit, the diagnosis needs revisiting rather than another prescription. See why antibiotics do not work on viruses and bronchitis versus pneumonia.

Related reading

• Night Sweats in Adults: Causes and When to See a Doctor
• Post-Viral Cough That Will Not Go Away: Why It Happens
• Dry Cough vs Wet Cough: What Each One Tells You

Sources

• MedlinePlus Medical Encyclopedia — U.S. National Library of Medicine
• Centers for Disease Control and Prevention
• Poison Help — 1-800-222-1222