A cough that won't go away: when should it be checked?

If you have been coughing for weeks after a cold, you most likely have no great cause for concern. But you should not wait indefinitely for a cough that won’t leave. This article sets out the criteria that reliable sources give. The diagnosis comes from a doctor’s examination and, sometimes, tests.

When does a cough count as “long”?

The sources do not agree on the cut-off.

• The NHS writes that a cough usually clears up within three to four weeks. It calls a cough lasting more than three weeks a “persistent cough” and advises having it seen by a doctor.
• The ATS sorts coughs into three groups: acute (under three weeks), subacute (three to eight weeks) and chronic (more than eight weeks without going away).

So if your cough has gone past three weeks, seeing a doctor is reasonable, and if it has gone past eight weeks, both sources say it now needs to be investigated. But the number of weeks is not the only yardstick. The accompanying signs matter more, and they are listed below.

Common causes

The NHS writes that most coughs are caused by a cold or flu, and that a cough is rarely a sign of something serious such as lung cancer. Other causes the NHS lists: smoking, acid reflux, allergies such as hay fever, infections such as bronchitis and COVID, and postnasal drip.

For chronic cough, the ATS considers these causes common:

• Inflammation of the nose or sinuses because of allergy or infection.
• Asthma that is not well controlled. The ATS reminds readers that a cough may be the first sign that asthma is not under control.
• A lung problem with infection, such as bronchiectasis (the cough is usually productive, with phlegm).
• Smoking, marijuana or e-cigarettes.
• Acid reflux from the stomach into the oesophagus.

Medicines can also be a cause. The ATS writes that one common group of blood pressure and heart failure medicines (ACE inhibitors) causes a cough. If you started coughing after beginning a new medicine, tell your doctor and do not stop the medicine yourself.

In COPD, a persistent cough with phlegm is common, and the NHS says many people call it a “smoker’s cough” and don’t take it seriously. In pulmonary fibrosis, a dry cough is seen (NHS).

Which signs mean you shouldn’t wait?

Urgent (call 115, Iran’s emergency number, right now):

• You are coughing up blood and the amount is more than a few spots or streaks (NHS).
• The cough comes with severe shortness of breath, blue lips or skin, sudden confusion or severe chest pain. The NHS says that if you are gasping and cannot get words out, you should get emergency help.

See a doctor the same day:

• Any amount of blood in your phlegm, even a few spots (the NHS says this needs to be seen promptly).
• A very severe cough, a rapidly worsening cough, or when you cannot stop coughing.
• Feeling generally unwell, chest pain, swelling and pain at the side of the neck, or breathlessness (NHS).

Book an appointment soon:

• The ATS also counts these as reasons to contact a doctor: a cough that makes you vomit, unexplained weight loss, a cough that first improved and then got worse, and, in someone with asthma or another lung disease, a cough that keeps coming back. A cough lasting more than eight weeks is on the same list.
• The NHS also lists unexplained weight loss and a weakened immune system (for example during chemotherapy or with diabetes), together with a cough lasting more than three weeks, as reasons to see a doctor.

When should we think about tuberculosis?

The NHS writes that the symptoms of TB usually start gradually: a cough lasting more than three weeks that may bring up phlegm, sometimes bloody, a fever or night sweats, unexplained weight loss and loss of appetite, and tiredness. So if a cough of more than three weeks comes with fever, night sweats or weight loss, or you have had close contact with someone who has TB with symptoms, tell your doctor so that TB can be looked into as well. The NHS says diagnosis is by a chest scan and a phlegm test, and that active TB is treated with antibiotics, usually for at least six months. The ATS also reminds readers that TB spreads to other people through coughing. An important point: if the medicines are started, take them to the end, even when you feel better.

This reminder is not meant to frighten you. Most long coughs are not TB. But because TB can be treated and looking for it is straightforward, it is worth telling your doctor the symptoms.

What to do before the appointment

• The ATS says to note how long you have been coughing. The doctor will ask whether it is dry or productive, whether it wakes you at night, and whether anything other than illness sets it off.
• Bring a list of all your medicines, including blood pressure medicine.
• Bring any previous CT scans and X-rays, and, if you have asthma or COPD, your inhalers.
• Say whether you smoke, use a hookah or use e-cigarettes. This question is not about judging you; it is about finding the cause.

What should we do until it has been checked?

The ATS says that if you have a lung disease, you should talk to your doctor before using over-the-counter cough medicines, because they may have side effects or interactions. The NHS and ATS recommend giving up smoking and avoiding smoke. To prevent spreading infection, cover your mouth and nose with a tissue or your sleeve when you cough, and wash your hands (ATS). Do not use herbs or home syrups in place of an assessment.

If no cause is found even after investigation, the ATS says to tell your doctor and ask about referral to a specialist cough clinic. “Just live with this cough” is not the end of the road.

In short

A cough that has gone past three weeks should be shown to a doctor. Past eight weeks, without fail. If there is blood, shortness of breath, unexplained weight loss, fever or night sweats, sooner. If there is a lot of blood or you are gasping for breath, call 115.