Blood in Your Cough: Causes and When to See a GP Immediately

• 03 Nov 2025

Coughing up blood — even in small amounts — can be alarming. Whether it’s streaks of red in your phlegm or a noticeable amount of blood when you cough, this symptom should never be ignored. In most cases, blood in your cough (haemoptysis) results from a minor issue such as a throat irritation or a chest infection. However, it can sometimes be a sign of a more serious underlying condition that needs medical attention.

In this article, we’ll explain the common causes of coughing up blood, when it’s time to see a GP, and what to expect during a medical evaluation. Understanding the difference between mild and serious causes can help you act quickly and appropriately if this symptom appears.

What Does It Mean If You’re Coughing Up Blood?

Coughing up blood — medically known as haemoptysis — means that blood from somewhere in your airways, lungs, or throat has mixed with your saliva or mucus. The blood may appear bright red, pink, or rusty in colour and can vary in amount from tiny streaks to larger clots.

It’s important to distinguish between coughing up blood and bleeding from elsewhere in the mouth or digestive tract. Blood from the stomach, for example, tends to look darker and may appear with vomiting rather than coughing.

Even if the bleeding appears mild, it’s crucial to contact a GP. Persistent or unexplained blood in your cough should always be professionally assessed.

Common Causes of Blood in the Cough

While coughing up blood can sound serious, it’s not always caused by life-threatening conditions. Some cases are mild and resolve on their own, while others need prompt treatment.

Here are some of the most common causes:

1. Respiratory Infections

Infections such as bronchitis, pneumonia, or tuberculosis can cause inflammation and small blood vessel damage in the lungs or airways. When you cough forcefully, these tiny vessels can rupture, leading to small streaks of blood in your mucus.

1. Chronic Cough or Throat Irritation

A persistent cough from allergies, viral infections, or acid reflux can irritate your throat and cause capillaries to burst. This usually leads to small amounts of blood rather than heavy bleeding and is not typically dangerous — but it still warrants a GP review if it continues.

1. Smoking

Tobacco smoke damages the lining of your airways, increasing the risk of chronic bronchitis, lung infections, and even lung cancer. Smokers are more likely to experience occasional bleeding due to irritation or inflammation in the lungs.

1. Chest Infections or Bronchiectasis

Bronchiectasis is a condition where the airways become widened and scarred, often leading to chronic infections, excessive mucus production, and occasional bleeding. A chest infection can also inflame airways, causing temporary blood-streaked sputum.

1. Lung Cancer or Tumours

In some cases, coughing up blood may be a symptom of lung cancer or another tumour in the respiratory tract. This is especially concerning if the blood is accompanied by unexplained weight loss, shortness of breath, or a persistent cough lasting longer than three weeks.

1. Pulmonary Embolism (Blood Clot in the Lung)

This is a medical emergency. A pulmonary embolism occurs when a blood clot blocks an artery in the lung. It can cause chest pain, sudden breathlessness, and coughing up blood. Call 999 immediately if these symptoms occur.

1. Trauma or Injury

Physical injuries to the chest or airways, or even medical procedures like bronchoscopy, can sometimes cause minor bleeding.

1. Underlying Medical Conditions

Certain heart or blood disorders, autoimmune diseases, or use of blood-thinning medications can make bleeding more likely, even from mild irritation.

When Should You See a GP Immediately?

It can be difficult to know whether coughing up blood requires an urgent GP visit or emergency care. The general rule: if in doubt, always err on the side of caution.

You should see a GP immediately if:

• You’ve noticed blood in your cough more than once
• The bleeding persists beyond a day or two
• You have a persistent cough that’s lasted more than 3 weeks
• You have accompanying symptoms such as fever, chest pain, or unexplained fatigue
• You are a smoker or have a history of lung disease

Call 999 or go to A&E right away if:

• You are coughing up large amounts of blood (more than a few teaspoons)
• You experience shortness of breath or chest pain
• You feel faint, dizzy, or have a rapid heartbeat
• You recently had a chest injury or surgery

Even small amounts of blood in your cough should never be ignored, especially if it happens repeatedly or is accompanied by other symptoms.

What Will the GP Do?

When you visit your GP, they will begin by taking a thorough medical history — asking about your smoking habits, past illnesses, medications, and when the bleeding started. They may then carry out a physical examination and order additional tests to find the cause.

Common diagnostic tests include:

• Chest X-ray: To identify infections, tumours, or other lung abnormalities.
• CT scan: Provides detailed imaging for more complex or uncertain cases.
• Sputum test: Examines mucus for infection, bacteria, or cancer cells.
• Blood tests: To check for anaemia, clotting problems, or infection.
• Bronchoscopy: A small camera inserted into the airways to directly inspect the source of bleeding.

Your GP may refer you to a respiratory specialist if the cause is not immediately clear or if more advanced evaluation is needed.

How Is Coughing Up Blood Treated?

The treatment for coughing up blood depends on the underlying cause.

• Infections: Usually treated with antibiotics (for bacterial causes) or rest and hydration (for viral infections).
• Bronchiectasis or chronic conditions: Managed with medication, physiotherapy, and regular monitoring.
• Lung cancer or tumours: May require surgery, chemotherapy, or radiotherapy.
• Pulmonary embolism: Requires urgent hospital treatment with blood-thinning medication.
• Minor irritation or injury: Usually resolves once the underlying irritation or cough subsides.

Your GP will tailor the treatment plan based on the diagnosis and your overall health.

Preventing Blood in Your Cough

You can lower your risk of experiencing blood in your cough by following these preventive measures:

1. Quit smoking: This is the single most effective way to protect your lungs.
2. Treat respiratory infections early: Don’t let chest infections linger — seek treatment promptly.
3. Stay hydrated: Adequate fluids keep your airways moist and help prevent irritation.
4. Avoid environmental irritants: Limit exposure to pollution, dust, and chemical fumes.
5. Follow medical advice carefully: Especially if you’re on blood thinners or have chronic lung conditions.
6. Get vaccinated: Annual flu and pneumonia vaccines can help prevent severe respiratory infections that cause bleeding.

When Coughing Up Blood Is Not Serious

Sometimes, a tiny streak of blood in mucus may result from vigorous coughing, throat irritation, or even dry air. If it happens once and resolves quickly, it’s usually not a cause for alarm. However, if it recurs or worsens, always book a GP appointment to rule out more serious causes.

Key Takeaway

Coughing up blood should never be ignored — even small streaks can indicate something that needs medical attention. Early diagnosis is crucial for successful treatment, especially if the bleeding is linked to infection, lung disease, or another serious condition.

If you ever experience blood in your cough, don’t wait to see if it disappears. A qualified GP can assess your symptoms, perform necessary tests, and provide peace of mind.

Conclusion

Noticing blood in your cough can be unsettling, but prompt medical evaluation helps identify the cause and ensures you receive the right care quickly. Whether the reason is a minor infection or a more serious lung condition, early intervention is key to protecting your health.

If you are experiencing this symptom or need an urgent GP consultation in London, reach out to the trusted medical professionals at Private Doctor London. Their experienced GPs offer same-day appointments, advanced diagnostics, and compassionate care — helping you get answers and relief when it matters most.