Causes of Persistent Cough and When to See a GP

• 26 Sep 2025

A cough is one of the body’s natural defence mechanisms, helping to clear the airways of mucus, irritants, or infections. But when a cough lingers for weeks without improvement, it raises concern. A persistent cough can be more than just a minor irritation — it may be a sign of an underlying condition that needs medical attention.

In this guide, we’ll explain the common causes of a persistent cough, highlight when it could signal something serious, and discuss when to see a GP for cough symptoms.

What Is a Persistent Cough?

Doctors generally define a persistent or chronic cough as one that lasts longer than 3 weeks. While most short-term coughs are caused by viral infections like the common cold, a lingering cough can have many other possible triggers.

A cough lasting more than 8 weeks in adults (or 4 weeks in children) should always be taken seriously. If you’ve been wondering, “How long should a cough last before seeing a doctor?” — the answer is straightforward: if it goes beyond 3 weeks, you should book an appointment.

Common Causes of Persistent Cough

There are several possible explanations for an ongoing cough that won’t go away. Some of the most common include:

1. Post-Viral Cough

After a cold, flu, or respiratory infection, irritation in the airways may remain even after the infection has cleared. This can cause a persistent dry cough lasting weeks.

2. Asthma

Asthma is a frequent cause of chronic cough, especially in children and young adults. It may be accompanied by wheezing, breathlessness, or chest tightness.

3. Allergies and Hay Fever

Exposure to dust, pollen, pet dander, or mould can trigger an ongoing cough as part of the body’s allergic response.

4. Acid Reflux (GORD)

Gastro-oesophageal reflux disease (GORD) can cause stomach acid to flow back into the throat, irritating the airways and leading to a cough, particularly at night.

5. Smoking

Smokers often experience a persistent cough with phlegm due to irritation and long-term lung changes. This is sometimes referred to as a “smoker’s cough.”

6. Medication Side Effects

Certain blood pressure medications, such as ACE inhibitors, list chronic cough as a common side effect.

Serious Causes of Persistent Cough

While most cases are harmless, sometimes a persistent cough is a sign of something serious. It’s important to be aware of potential red flags:

• Chronic Obstructive Pulmonary Disease (COPD): Often linked to smoking, COPD includes conditions like chronic bronchitis and emphysema.
• Pneumonia or other infections: If accompanied by fever, chest pain, or coloured phlegm.
• Tuberculosis (TB): Less common but still a possible cause of a cough lasting more than 8 weeks.
• Lung Cancer: A persistent cough, particularly when paired with coughing up blood or unexplained weight loss, requires urgent assessment.

If you’re concerned about underlying conditions, your GP may recommend investigations such as blood testing in London, chest X-rays, or specialist referrals. For more information on diagnostic options, see Private Doctor London’s blood testing services .

When to See a GP for a Persistent Cough

Not every cough requires a doctor’s visit, but there are clear situations where you should seek medical help.

You should see a GP if your cough:

• Lasts longer than 3 weeks.
• Produces blood or rust-coloured phlegm.
• Is accompanied by chest pain, shortness of breath, or wheezing.
• Comes with unexplained weight loss, night sweats, or fatigue.
• Gets worse instead of improving.

Seek urgent medical attention if:

• You’re coughing up significant amounts of blood.
• You experience sudden shortness of breath or chest pain.
• Your cough is accompanied by high fever or confusion.

Wondering “Could a persistent cough be a sign of something serious?” — the answer is yes, which is why timely medical evaluation is so important.

What to Expect at a GP Appointment

During your appointment, a GP will take a full history and may perform a physical examination of your chest, lungs, and throat. Depending on your symptoms, possible next steps include:

• Blood tests to check for infections or other conditions.
• Chest X-rays or CT scans for a closer look at the lungs.
• Spirometry to assess lung function in suspected asthma or COPD.
• Referral to specialists for further investigation if necessary.

Private practices can often arrange same-day appointments and diagnostic tests. For example, you can review transparent private GP consultation fees in London before booking.

Treating a Persistent Cough

The right treatment depends on the underlying cause. Some common approaches include:

• Asthma: Inhalers or other medications to control inflammation.
• Allergies: Antihistamines or avoidance strategies.
• Acid reflux: Dietary adjustments, medication, and lifestyle changes.
• Infections: Antibiotics (if bacterial) or supportive care (if viral).
• Smoking-related cough: Quitting smoking and lung health monitoring.

Remember, self-medicating with cough syrups won’t always solve the problem if the cause is something more serious.

FAQs About Persistent Cough

How long should a cough last before seeing a doctor?

If your cough continues for more than 3 weeks, book a GP appointment.

Is a persistent cough always serious?

Not always — common causes include allergies or post-viral irritation. But some cases can indicate serious illness.

What does a persistent dry cough mean?

It may be linked to asthma, acid reflux, or even certain medications.

Can a persistent cough be treated at home?

While you can soothe symptoms with fluids and rest, the root cause often requires medical evaluation.

Could my cough be due to smoking?

Yes — smoking is a leading cause of chronic cough in adults.

Final Thoughts

A persistent cough can be irritating, worrying, and disruptive to daily life. While most cases are linked to minor causes like allergies, infections, or acid reflux, sometimes they signal more serious conditions. Knowing when to see a GP for cough symptoms is crucial for timely diagnosis and effective treatment.

If you’ve been dealing with a cough that won’t go away, don’t ignore it. Booking a consultation with a private GP in London ensures you get fast access to care, personalised attention, and same-day testing when needed. For expert help and discreet medical support, visit Private Doctor London.